Arctic Sea Ice : Forum

AGW in general => Science => Topic started by: ArcticMelt2 on May 30, 2019, 05:11:33 AM

Title: Magnitude of future warming
Post by: ArcticMelt2 on May 30, 2019, 05:11:33 AM
It is interesting to know the opinion of people on the forum about the magnitude of future warming. Official (conservative) forecasts indicate a warming of 2 degrees by 2100.

Other studies are inclined to 10 degrees.

https://phys.org/news/2016-06-future-global-warmer.html
Quote
"Our results show that the amount of carbon that drove the PETM warming was about the same amount as the current 'easily accessible' fossil fuel reserves of about 4,000 billion tons. But the warming that would result from adding such large amounts of carbon to the climate system would be much greater today than during the PETM and could reach up to 10 degrees.

Finally, third scientists believe that warming will turn the planet into a Venusian steam room, and space colonization will be the only salvation.

https://www.forbes.com/sites/ericmack/2017/11/07/stephen-hawking-apocalypse-2600-fireball-earth-breakthrough-starshot/

Quote
Speaking at the Tencent WE Summit Sunday, Hawking warned that overpopulation and extreme energy consumption will turn Earth into a fire ball by the year 2600.
Title: Re: How big is AGW?
Post by: ArcticMelt2 on May 30, 2019, 05:54:51 AM
There are estimates that the climate sensitivity may be 12 degrees.

(https://www.climateemergencyinstitute.com/uploads/climate_sensitivity_NASA_blocks.png)
Title: Re: How big is AGW?
Post by: ArcticMelt2 on May 30, 2019, 05:59:25 AM
Another interesting thing is that with the growth of the starting temperature increases and the size of warming.

That is, it can be a vicious circle. Slight warming with each step further increases the warming (due to feedbacks - water vapour, the decrease in albedo due to melting ice, melting methanehydrates and permafrost, deforestation).
Title: Re: Magnitude of future warming
Post by: be cause on May 30, 2019, 11:03:46 AM
Vote closes in 2099 ? b.c.
Title: Re: Magnitude of future warming
Post by: b_lumenkraft on May 30, 2019, 11:12:43 AM
Are you impatient or what?  ;)
Title: What units?
Post by: pietkuip on May 30, 2019, 12:58:22 PM
Centigrade or Fahrenheit? Please clarify the question.
Title: Re: Magnitude of future warming
Post by: b_lumenkraft on May 30, 2019, 01:11:24 PM
Why would anyone using Fahrenheit??  ???
Title: Re: Magnitude of future warming
Post by: Tom_Mazanec on May 30, 2019, 06:25:52 PM
I assumed C, since this is on the World Wide Web and not the United States Wide Web.
Title: Re: Magnitude of future warming
Post by: interstitial on May 30, 2019, 08:22:07 PM
Why would anyone using Fahrenheit??  ???
to confuse foreigners. ;D
Title: Re: Magnitude of future warming
Post by: Shared Humanity on May 31, 2019, 01:50:49 AM
The problem with this question is that it involves the value for ECS but it also has to take into account whether we will take effective action to curb CO2 emissions. I do not think we will act quickly enough to eliminate anthropogenic emissions and expect us to blow past a doubling of ppm from preindustrial (560 ppm) by shortly after mid century at the latest. My uneducated guess is 4C to 5C.

A temperature increase that has been described as incompatible with human civilization.
Title: Re: Magnitude of future warming
Post by: Tom_Mazanec on May 31, 2019, 03:39:08 AM
I expect about 4 C. I voted 3-4, but could just as easily have voted for 4-5.
Title: Re: Magnitude of future warming
Post by: KiwiGriff on May 31, 2019, 04:14:34 AM
I just voted 3 to 4C for this century.
The consensus value for Equilibrium Climate Sensitivity appears to be around 3C.
I doupt we will mange to contain CO2e under 2X. Some processes like cement  and steel manufacturing will involve some on going emissions even if with do away with FF use. At these levels of warming the outlook for a coherent effort from human civilization is dire. A fractured human civilization will find it harder to maintain a reduced level of emissions long term.
The  Longer term Earth System Sensitivity will drive us well over 4C by the end of  next century unless we discover an as yet unknown technology to economically remove CO2 from the atmosphere.
Title: Re: Magnitude of future warming
Post by: Sleepy on May 31, 2019, 08:13:50 AM
The problem with this question is that it involves the value for ECS but it also has to take into account whether we will take effective action to curb CO2 emissions. I do not think we will act quickly enough to eliminate anthropogenic emissions and expect us to blow past a doubling of ppm from preindustrial (560 ppm) by shortly after mid century at the latest. My uneducated guess is 4C to 5C.

A temperature increase that has been described as incompatible with human civilization.
Indeed. And it's not uneducated at all.
The rosy picture is that current policies gives a median of 3.3°C.

http://claimthesky.org/ (http://claimthesky.org/)
Title: Re: Magnitude of future warming
Post by: ArcticMelt2 on May 31, 2019, 09:05:19 AM
I personally tend to believe that the final warming will be from 10 or more degrees Celsius.

This is due to the fact that the rate of today's greenhouse gas emissions is tens and hundreds of times past events.

For example, 10-20 thousand years ago, the ocean threw CO2 in 100 times slower than people throw out now:

(https://ane4bf-datap1.s3-eu-west-1.amazonaws.com/wmocms/s3fs-public/styles/featured_media_detail/public/news/featured_media/pr_1.jpg?.Q4AcBvO2Z_6ZlQvSG6LBtlu4J0Vh3Pc&itok=cHU8MN_9)

In this regard, the ice sheets will collapse 100 times faster than 10-20 thousand years ago. This will cause an unprecedented destabilization of tectonic plates and degassing of the mantle.

It reminds me of a fresh film in which a small jolt leads to the formation of a monstrous wave.

https://www.youtube.com/watch?v=6Tko0bctqrY
Title: Re: Magnitude of future warming
Post by: b_lumenkraft on May 31, 2019, 09:24:56 AM
This will cause an unprecedented destabilization of tectonic plates and degassing of the mantle.

... which will cause volcano eruptions all around the world, which will reduce the temperatures again. At least, this is my layman understanding. Correct me if i'm wrong.

A plus 10-degree scenario is a scenario where humans most likely can't exist, right?

The question is, when will tectonics kick in and cause these disruptions? We can't possibly know, or can we?

Which leads to the question, for how long humanity manages to make this planet uninhabitable for higher life?
Title: Re: Magnitude of future warming
Post by: ArcticMelt2 on May 31, 2019, 09:50:09 AM
... which will cause volcano eruptions all around the world, which will reduce the temperatures again. At least, this is my layman understanding. Correct me if i'm wrong.

Unfortunately, long-term cooling does not work. Sulfur sprays precipitate much faster than carbon dioxide. After the volcanoes calm down, the temperature will rise to huge values.

A plus 10-degree scenario is a scenario where humans most likely can't exist, right?

At 10 degrees, the average temperature of the planet will be about 24 degrees Celsius. It will be more tolerable for people. But if this value is exceeded, the planet will turn into a total desert.

The question is, when will tectonics kick in and cause these disruptions? We can't possibly know, or can we?

Which leads to the question, for how long humanity manages to make this planet uninhabitable for higher life?

Tectonics due to melting glaciers is already growing. In the 21st century, the number of the strongest earthquakes is much higher than the average in the 20th century.

But the melting rate of glaciers has not yet exceeded the average melting rate of 10-20 thousand years. Warming requires several more decades to disperse and incorporate all feedbacks (warming the ocean and releasing water vapor, melting permafrost, etc.).
Title: Re: Magnitude of future warming
Post by: b_lumenkraft on May 31, 2019, 10:05:51 AM
Unfortunately, long-term cooling does not work. Sulfur sprays precipitate much faster than carbon dioxide. After the volcanoes calm down, the temperature will rise to huge values.

That's a good point.  :-\
Title: Re: Magnitude of future warming
Post by: Wherestheice on May 31, 2019, 10:15:01 AM
5-6 C. Feedback loops tend to be forgotten often. Tons of people think we just have to stop emitting co2 and then we will be fine, but that is false.

This 5-6 C rise in temp is likely going to wipe out most life on the planet as well as our species.... or at least a large percent of us. Civilization probably has till mid century
Title: Re: Magnitude of future warming
Post by: Klondike Kat on May 31, 2019, 02:18:20 PM
5-6 C. Feedback loops tend to be forgotten often. Tons of people think we just have to stop emitting co2 and then we will be fine, but that is false.

This 5-6 C rise in temp is likely going to wipe out most life on the planet as well as our species.... or at least a large percent of us. Civilization probably has till mid century

Negative feedback loops tend to be forgotten also.  But that is not my main reason that 5-6 C will not occur this century.  Assuming the current rate of rise for CO2 continues unabated, we will hit a doubling of pre-industrial levels around 2100.  At a climate sensitivity of 3C/doubling, that level of temperature rise will not occur, especially since that is for equilibrium.  Equilibrium will not be obtained for some time thereafter, so the more apt number to use for near-term temperature rise would be the transient climate sensitivity, which is much less.  Hence, 3C should be considered a maximum for temperature rise this century, and the likelihood exists for a lower rise.
Title: Re: Magnitude of future warming
Post by: Archimid on May 31, 2019, 02:46:46 PM
I voted not enough information.  Whatever the ECS is today, it won't be by 2100.  Changes like no arctic sea ice with its corresponding changes in atmospheric and oceanic behaviors,  SLR, Ocean warming changing oceanic patterns, melting permafrost, etc  make ECS estimates unstable.

Honestly, I'm not even sure if warming will continue after the first BOE. I think that chances are that the first BOE leads to a very significant increase of the ECS. But there  is a chance that the opposite happens but it would require truly extraordinary snow cover, significantly decreasing NH albedo.

In either case it wouldn't matter. It will suck for us.

I would love to see a poll for "what is a safe ECS?" or something like that.
Title: Re: Magnitude of future warming
Post by: Shared Humanity on May 31, 2019, 09:31:35 PM
Assuming the current rate of rise for CO2 continues unabated, we will hit a doubling of pre-industrial levels around 2100. 

How do you figure this? We are currently at nearly 415 ppm and recent annual increases, week over week are > 3 ppm.

https://forum.arctic-sea-ice.net/index.php/topic,2541.100.html

Meanwhile, increases in atmospheric CO2 are accelerating.

https://www.esrl.noaa.gov/gmd/ccgg/trends/full.html

https://www.esrl.noaa.gov/gmd/ccgg/trends/gr.html

A 3 ppm increase year over year is the best we can expect over the next couple of decades and that is only if we first hold and then reduce emissions which we currently are not doing. At 3 ppm increase per year, we will have doubled CO2 concentrations over preindustrial by 2070 and this is assuming that positive feedbacks that reduce natural carbon sinks (drying of rainforests) or increase carbon release (permafrost thawing) do not kick in.
Title: Re: Magnitude of future warming
Post by: Shared Humanity on May 31, 2019, 09:44:35 PM

At 10 degrees, the average temperature of the planet will be about 24 degrees Celsius. It will be more tolerable for people. But if this value is exceeded, the planet will turn into a total desert.


Please tell me I am reading this wrong. You are not suggesting that a 10C rise in average temperature will be more tolerable are you?
Title: Re: Magnitude of future warming
Post by: FrostKing70 on May 31, 2019, 09:53:51 PM
I went with 4-5, as the current consensus is 3.3, but that has increased in the last decade as we understand the world better.   

I project that it will increase again over the next decade as our knowledge grows and, unfortunately, our emissions stay the same or increase slightly.
Title: Re: Magnitude of future warming
Post by: Klondike Kat on May 31, 2019, 11:45:50 PM
Assuming the current rate of rise for CO2 continues unabated, we will hit a doubling of pre-industrial levels around 2100. 

How do you figure this? We are currently at nearly 415 ppm and recent annual increases, week over week are > 3 ppm.

https://forum.arctic-sea-ice.net/index.php/topic,2541.100.html

Meanwhile, increases in atmospheric CO2 are accelerating.

https://www.esrl.noaa.gov/gmd/ccgg/trends/full.html

https://www.esrl.noaa.gov/gmd/ccgg/trends/gr.html

A 3 ppm increase year over year is the best we can expect over the next couple of decades and that is only if we first hold and then reduce emissions which we currently are not doing. At 3 ppm increase per year, we will have doubled CO2 concentrations over preindustrial by 2070 and this is assuming that positive feedbacks that reduce natural carbon sinks (drying of rainforests) or increase carbon release (permafrost thawing) do not kick in.

Not sure where you are getting your numbers, but the annual CO2 rise has averaged 2.2 pts over the past decade.  Doubling would occur shortly before we reach the end of the century.  That is assume no change in positive or negative feedbacks.
Title: Re: Magnitude of future warming
Post by: Shared Humanity on June 01, 2019, 12:46:48 AM
And the annual increase for 3 of the last 4 years is over 2.8 ppm...

https://www.esrl.noaa.gov/gmd/ccgg/trends/gr.html

...while the linear trend suggests CO2 will increase by 2.6 ppm this year and we should expect this to continue to increase.
Title: Re: Magnitude of future warming
Post by: KiwiGriff on June 01, 2019, 06:04:19 AM
Global financial crisis 2007 to 2008. Emissions shrank along with the global economy for a number of years.
So the start point was effected by circumstance .
We then use an average for the entire period rather than the much more important trend
After all the the measurement of CO2 is  referred to as the keeling curve for a very simple reason. Acceleration.

As this forum is mostly populated by the informed an interesting distraction .
But for our purpose .
The important number for humanity is  CO2e not CO2.

 
Title: Re: Magnitude of future warming
Post by: Klondike Kat on June 01, 2019, 02:50:18 PM
True on both points.  Projecting long term trends using short term data is a questionable practice.  Using an inappropriate dataset makes it worse.
Title: Re: Magnitude of future warming
Post by: Shared Humanity on June 01, 2019, 03:02:37 PM
True on both points.  Projecting long term trends using short term data is a questionable practice.  Using an inappropriate dataset makes it worse.

Not sure how the data set collected by the Scripps Institution of Oceanography is inappropriate.

https://www.esrl.noaa.gov/gmd/ccgg/trends/full.html

https://www.esrl.noaa.gov/gmd/ccgg/trends/gr.html

Both of these charts clearly show that the growth rate in atmospheric CO2 is increasing. Between 1960 and 1970, CO2 increased by 1ppm annually. Between 1990 to 2000, it increased by 2ppm annually.

What data set would you use to evaluate the growth rates in atmospheric CO2?
Title: Re: Magnitude of future warming
Post by: gerontocrat on June 01, 2019, 03:40:06 PM
True on both points.  Projecting long term trends using short term data is a questionable practice.  Using an inappropriate dataset makes it worse.
We have long-term data to show that CO2 emissions have increased.
We have many studies to show that the efficiency of the world's carbon sinks have declined over time.
We know that over the life of the CO2 keeling curve CO2 ppm annual increase has gradually accelerated.

We know that on a BAU basis CO2 emissions will increase and environmental degradation will increase.

So it is reasonable to project what that means for CO2 ppm for the future based on certain assumptions, including the pessimistic scenario - including that carbon capture and sequestration efforts will at best be marginal, which the IPCC scenarios do or do not accept?

Me, what was my Armageddon scenario (made 2 years ago) of CO2 450 ppm by the early 2030's is now looking somewhat more reasonable. (Mind you, Trump's antics might be the trigger that tips the world economy into recession or even depression).

Beware left field...
Title: Re: Magnitude of future warming
Post by: crandles on June 01, 2019, 04:04:01 PM

At 10 degrees, the average temperature of the planet will be about 24 degrees Celsius. It will be more tolerable for people. But if this value is exceeded, the planet will turn into a total desert.


Please tell me I am reading this wrong. You are not suggesting that a 10C rise in average temperature will be more tolerable are you?

Sounds a bit like like one foot in liquid nitrogen and one in boiling water such that average temp is a nice comfortable level so everything must be ok.
Title: Re: Magnitude of future warming
Post by: Klondike Kat on June 01, 2019, 04:29:05 PM
True on both points.  Projecting long term trends using short term data is a questionable practice.  Using an inappropriate dataset makes it worse.

Not sure how the data set collected by the Scripps Institution of Oceanography is inappropriate.

https://www.esrl.noaa.gov/gmd/ccgg/trends/full.html

https://www.esrl.noaa.gov/gmd/ccgg/trends/gr.html

Both of these charts clearly show that the growth rate in atmospheric CO2 is increasing. Between 1960 and 1970, CO2 increased by 1ppm annually. Between 1990 to 2000, it increased by 2ppm annually.

What data set would you use to evaluate the growth rates in atmospheric CO2?

There was nothing wrong with the dataset.  It was your extrapolation of the past decade out to the end of the century that I was criticizing.
Title: Re: Magnitude of future warming
Post by: Shared Humanity on June 01, 2019, 08:55:49 PM
True on both points.  Projecting long term trends using short term data is a questionable practice.  Using an inappropriate dataset makes it worse.

Not sure how the data set collected by the Scripps Institution of Oceanography is inappropriate.

What data set would you use to evaluate the growth rates in atmospheric CO2?

There was nothing wrong with the dataset.  It was your extrapolation of the past decade out to the end of the century that I was criticizing.

But, of course, that is not what you said. You pointed out that my extrapolation using only a decade of data was wrong (perhaps you are correct) and then you specifically stated that the data set I drew it from was inappropriate.

The reason I used the last decade is that it suggests this trend that we see over the last 60 years of accelerating growth in CO2 levels is continuing to grow. The growth rate in three of the last four years is very close to 3 ppm.

I would suggest using an arbitrary annual growth rate (say 2.2 ppm per year) that we have already blown past and will never see again in my lifetime to project a doubling of atmospheric CO2 by 2100 is far more inappropriate than my suggesting the acceleration in the growth of atmospheric CO2 will continue into the future.
Title: Re: Magnitude of future warming
Post by: Klondike Kat on June 01, 2019, 09:51:13 PM
True on both points.  Projecting long term trends using short term data is a questionable practice.  Using an inappropriate dataset makes it worse.

Not sure how the data set collected by the Scripps Institution of Oceanography is inappropriate.

What data set would you use to evaluate the growth rates in atmospheric CO2?

There was nothing wrong with the dataset.  It was your extrapolation of the past decade out to the end of the century that I was criticizing.

But, of course, that is not what you said. You pointed out that my extrapolation using only a decade of data was wrong (perhaps you are correct) and then you specifically stated that the data set I drew it from was inappropriate.

The reason I used the last decade is that it suggests this trend that we see over the last 60 years of accelerating growth in CO2 levels is continuing to grow. The growth rate in three of the last four years is very close to 3 ppm.

I would suggest using an arbitrary annual growth rate (say 2.2 ppm per year) that we have already blown past and will never see again in my lifetime to project a doubling of atmospheric CO2 by 2100 is far more inappropriate than my suggesting the acceleration in the growth of atmospheric CO2 will continue into the future.

The inappropriate comment was based on the intervening post, and was most likely a mistake on my part.  Sorry, I commented before thinking it through.  With regards to the annual rise, the trend starts during the recession, and ends just after the most recent El Niño, so I think that we have only “blown past” the average growth rate on a temporary basis.  Remember, the annual rise was higher during the 1998 El Niño, but fell back down during the ensuing decade.  While we will probable experience a 3 ppm rise during the next strong El Niño, I seriously doubt we will average that type of rise this century. Although most of this century remains to be played, so anything could happen.
Title: Re: Magnitude of future warming
Post by: oren on June 02, 2019, 09:32:52 AM
When CO2 annual growth shows long term acceleration over several decades, and when supporting trends like population growth and rising affluence are continuing, picking a desired constant number for that growth is what I personally consider as cherry-picking.
Title: Re: Magnitude of future warming
Post by: Shared Humanity on June 02, 2019, 04:12:51 PM
When CO2 annual growth shows long term acceleration over several decades, and when supporting trends like population growth and rising affluence are continuing, picking a desired constant number for that growth is what I personally consider as cherry-picking.

Agreed.

What is interesting about the NOAA data is that we see a doubling in the growth rate in 4 decades, 1 ppm annually from 1960 to 1970 to 2 ppm annually from 2000 to 2010. Will this trend of accelerating growth result in a doubling in the next 4 decades? If so, we will have an annual increase of 4 ppm in 2040 to 2050. This depends, I think, on the sources of CO2. How much of the current and future growth is and will be due directly to the burning of fossil fuels etc.? How much is and will be due to a shift in the behavior of carbon sinks?

I think we will make significant progress in cutting CO2 emissions by 2050 as the catastrophic nature of climate change becomes more obvious. Not sure about the behavior of carbon sinks. Sure hope we are not at 4 ppm annual increase in 2050. Fairly certain we will not be at 2.2 ppm annually.
Title: Re: Magnitude of future warming
Post by: Klondike Kat on June 02, 2019, 06:25:50 PM
When CO2 annual growth shows long term acceleration over several decades, and when supporting trends like population growth and rising affluence are continuing, picking a desired constant number for that growth is what I personally consider as cherry-picking.

Agreed.

What is interesting about the NOAA data is that we see a doubling in the growth rate in 4 decades, 1 ppm annually from 1960 to 1970 to 2 ppm annually from 2000 to 2010. Will this trend of accelerating growth result in a doubling in the next 4 decades? If so, we will have an annual increase of 4 ppm in 2040 to 2050. This depends, I think, on the sources of CO2. How much of the current and future growth is and will be due directly to the burning of fossil fuels etc.? How much is and will be due to a shift in the behavior of carbon sinks?

I think we will make significant progress in cutting CO2 emissions by 2050 as the catastrophic nature of climate change becomes more obvious. Not sure about the behavior of carbon sinks. Sure hope we are not at 4 ppm annual increase in 2050. Fairly certain we will not be at 2.2 ppm annually.

I do not think we will see a doubling of CO2 over that timeframe, even if we do absolutely nothing to cut emissions.  The main reason is that the global population doubled during the same timeframe that CO2 emissions doubled.  The population growth rate has slowed, and will likely continue to do so, possibly reaching s maximum before the end of the century.  This will naturally lead to slower emission growth.
Title: Re: Magnitude of future warming
Post by: SteveMDFP on June 02, 2019, 06:29:59 PM

I do not think we will see a doubling of CO2 over that timeframe, even if we do absolutely nothing to cut emissions.  The main reason is that the global population doubled during the same timeframe that CO2 emissions doubled.  The population growth rate has slowed, and will likely continue to do so, possibly reaching s maximum before the end of the century.  This will naturally lead to slower emission growth.

Possibly, but economic growth and thus standards of living and consumption are increasing in poorer countries, particularly in Asia.  Global GDP may be a better measure than population numbers.
Title: Re: Magnitude of future warming
Post by: bbr2314 on June 02, 2019, 07:12:47 PM
Check out the water thread. I would wager that countries like India et al will run out of the most basic essentials well before they reach developed standards of living outside of their 1era. Mass death will be the correction, not willfully sufficient adoption of green tech (IMO).
Title: Re: Magnitude of future warming
Post by: SteveMDFP on June 02, 2019, 07:28:58 PM
Check out the water thread. I would wager that countries like India et al will run out of the most basic essentials well before they reach developed standards of living outside of their 1era. Mass death will be the correction, not willfully sufficient adoption of green tech (IMO).

It will take a few years for India to divert rivers to cities to supply their masses adequately.  They run a clunky democracy there, but democracies do a pretty good job making sure their people don't starve or die of thirst.  It's dictatorships that allow mass deaths.
Title: Re: Magnitude of future warming
Post by: Archimid on June 02, 2019, 07:43:55 PM
Plan A is to bet our lives that climate change will not be harmful. This is nothing but religion and fear psychology.

Plan B is to let natural selection lower population and then the "fittest" will survive. LOLs at those who think that's plan. Climate change will redefine fitness. Those fit today can't possibly prepare for the changes at hand. And if they seal themselves into a vault with an army and enough food for a millennia, they still lose.
Title: Re: Magnitude of future warming
Post by: Tom_Mazanec on June 24, 2019, 06:55:14 PM
Warming in 2050 1.4 K to 3 K:
https://www.nature.com/articles/ngeo1430
Title: Re: Magnitude of future warming
Post by: vox_mundi on July 01, 2019, 06:22:10 PM
'Committed' CO2 Emissions Jeopardize International Climate Goals, Study Finds
https://phys.org/news/2019-07-committed-co2-emissions-jeopardize-international.html

The nations that have signed agreements to stabilize the global mean temperature by 2050 will fail to meet their goals unless existing fossil fuel-burning infrastructure around the world is retired early, according to a study—published today in Nature - by researchers at the University of California, Irvine and other institutions.

... According to the study, emissions from existing energy infrastructure take up the entire carbon budget to limit mean warming to 1.5 degrees Celsius and close to two-thirds of the budget to keep warming to under 2 C over the next three decades.

Although the pace of growth has slowed in recent years, a significant amount of new electricity-generating capacity has been proposed globally; some of it is already under construction. If this prospective infrastructure is built, total future emissions take up three-quarters of the budget to constrain warming to below 2 C.

The researchers also tested different lifetime assumptions in order to see how early CO2-emitting infrastructure might need to be retired in order to meet international climate goals. For example, a 1.5 C boost in mean temperature might still be avoided if current power plants were shuttered after 25, rather than 40 years of operation.

"Our results show that there's basically no room for new CO2-emitting infrastructure under the international climate goals," said co-author Steven Davis, a UCI associate professor of Earth system science. "Rather, existing fossil fuel-burning power plants and industrial equipment will need to be retired early unless they can be feasibly retrofitted with carbon capture and storage technologies or their emissions are offset by negative emissions. Without such radical changes, we fear the aspirations of the Paris agreement are already at risk."

Dan Tong, et.al., Committed emissions from existing energy infrastructure jeopardize 1.5 °C climate target (https://www.nature.com/articles/s41586-019-1364-3), Nature (2019)
Title: Re: Magnitude of future warming
Post by: wolfpack513 on July 04, 2019, 01:20:12 AM
Depending on your source we’re closer to 1.5°C than most realize.  5-year smooth above preindustrial is the preferred measurement.  Maybe less than decade depending on your benchmark.

GISS LOTI is approaching +1.2°C and currently warming at 0.2°C per decade.  You could even tack on another 0.1-0.2°C of warming based on Schurer et al. 2017 … that argues we’ve underestimated 19th century warming.
Title: Re: Magnitude of future warming
Post by: KiwiGriff on July 04, 2019, 03:44:00 AM
Quote
The nations that have signed agreements to stabilize the global mean temperature by 2050 will fail to meet their goals unless existing fossil fuel-burning infrastructure around the world is retired early, according to a study—published today in Nature - by researchers at the University of California, Irvine and other institutions.

... According to the study, emissions from existing energy infrastructure take up the entire carbon budget to limit mean warming to 1.5 degrees Celsius and close to two-thirds of the budget to keep warming to under 2 C over the next three decades.

Still does my head in that we see claims we can stay below 1.5C .
We shutter  Coal plants  we get most of the 0.4C that our aerosols emissions are shading us from  immediately. Add that there is some delay between CO2 emissions and warming giving another 0.2C or more the math for 1.5 C simply does not work.

In the longer term
Long distance transport , steel and cement manufacturing do not have viable economic solutions to their emissions as yet.  CCS is another technology solution  we do not have a viable answer to.
Taking these factors into account there is no real pathway towards net zero and reducing the 415ppm CO2 we have already achieved hence the 1.5C warming we have locked in .

The 1.5C target is just a mythical dream based on magic thinking  not an achievable goal

0.4C value for aerosols from Haustein et al, 2019 most of which is from burning FF's to make electricity .



Title: Re: Magnitude of future warming
Post by: Archimid on July 04, 2019, 03:55:25 AM
Quote
The 1.5C target is just a mythical dream based on magic thinking  not an achievable goal

It will require a miracle. Luckily, miracles do happen, usually to those working hard towards a goal.

Same with Climate change. If humanity mobilizes with the impetus of WW2, with the scientific determination of the space race, with a New Deal for the whole world where energy independence, conservation, recycling, reusability become the new world wide paradigm.

We do more, with less. We become richer with less, but better stuff. We plan our civilization to work together with nature.

It will also require considerable geoengineering.
Title: Re: Magnitude of future warming
Post by: Rod on July 04, 2019, 04:20:42 AM
Quote
The 1.5C target is just a mythical dream based on magic thinking  not an achievable goal

It will require a miracle. Luckily, miracles do happen, usually to those working hard towards a goal.



Wow! This is one of the most upbeat posts I have ever seen from you Archimid!   I hope you are right!

Personally, I’m more down beat.  I don’t have high hopes in geoengineering in the near term. I am also increasingly worried about positive feedbacks, and all of the additive effects that have not been accounted for in the models. It seems like every week there is a new study showing something else that has been missed. 

But such is life.  Hopefully we can solve this problem before shit hits the fan.  This forum focuses on arctic sea ice which is obviously a key component, but there are many more pieces to this problem.

Title: Re: Magnitude of future warming
Post by: Juan C. García on July 04, 2019, 06:05:32 AM
I expect about 4 C. I voted 3-4, but could just as easily have voted for 4-5.
+1

I don't know what to expect, but I am sure that we must pressure to stop emissions of GHG as soon as possible. So the final outcome will depend on our success (as human beings) in stopping GHG and even our capacity to take out CO2 from the atmosphere.


Great topic! I appreciate if someone finds more scientific essays on this subject.
Title: Re: Magnitude of future warming
Post by: Juan C. García on July 04, 2019, 06:17:15 AM
Quote
The 1.5C target is just a mythical dream based on magic thinking  not an achievable goal

It will require a miracle. Luckily, miracles do happen, usually to those working hard towards a goal.



Wow! This is one of the most upbeat posts I have ever seen from you Archimid!   I hope you are right!
I change to 2-3 °C, after reading Archimid's comment!  ;)
Title: Re: Magnitude of future warming
Post by: El Cid on July 04, 2019, 08:08:08 AM
it is quite impossibble to stop this process now even though I think that by 2050 we will be mostly carbon free. 3 C is all but guaranteed even if our whole economy turns quite sustainable. 4-5 C is also quite likely. This has already happened in Svalbard without the end of the world (4 C annual average rise, 7 C during winter - great article in the Guardian ,cited by gerontocrat in another thread)
Title: Re: Magnitude of future warming
Post by: wdmn on July 04, 2019, 08:15:58 AM
EDIT: Apologies, I read this as being how much warming was locked in as of now.


The IPCC says very little, because they believe that if emissions suddenly stopped the ocean would bring down atmospheric co2 concentrations. See attached image from the special report on 1.5C.

James Hansen says:

"We know quite accurately how much further warming is already ‘in the pipeline,’ because we are measuring Earth’s energy imbalance, which is +0.75 ±0.25 W/m2. Given global
climate sensitivity of 0.75°C per W/m2 well-established from Earth’s paleoclimate history, that means there is additional warming of about 0.5°C (about 1°F) on the way.

That climate sensitivity, which is 3°C for doubled CO2, accounts only for fast feedbacks. If we wait long enough for slow feedbacks to occur such as change of ice sheet size, the warming will be larger."

http://www.columbia.edu/~jeh1/mailings/2019/20190627_SavingEarth.pdf

i.e. 0.5C but that doesn't include the masking of aerosols. So if aerosols really are -0.4C that would give us 0.9C.

If ECS is closer to 4.3C (the median value of the early CMIP6 results), then perhaps with slow feedbacks are greater.
Title: Re: Magnitude of future warming
Post by: Rich on July 04, 2019, 01:02:16 PM
The magnitude of future warming. Interesting question.

The current CO2 level (I know it's not the only GHG) at 415 ppm is the highest it has been in ~3M years. Our trajectory is taking us to perhaps a 10M+year high.

50M years ago, the earth warmed 5-8C during the Paleocene Eocene Thermal Maximum. We need to be concerned that we don't trigger a similar event because that would pretty much end human civilization.

It's very difficult if not impossible to ascertain the degree feedback effects that will be triggered along the way to net zero eimissions. So temperature projection is somewhat guesswork.

If we stopped emitting GHG's immediately, we'd probably get an atmospheric temp bump from forcing inertia if 0.5C and another 0.5C from aerosol removal.

That's 2C +/- unknowns for feedbacks, geoengineering and length of time required to scale down emissions.
Title: Re: Magnitude of future warming
Post by: Shared Humanity on July 04, 2019, 01:50:45 PM
This forum focuses on arctic sea ice which is obviously a key component, but there are many more pieces to this problem.

This forum focuses on virtually anything related to AGW.
Title: Re: Magnitude of future warming
Post by: johnm33 on July 04, 2019, 03:01:46 PM
I went 2-3 had the question been about the Arctic I'd be about an order of magnitude higher.
Title: Re: Magnitude of future warming
Post by: magnamentis on July 04, 2019, 11:12:07 PM
Re: Magnitude of future warming

can you for the sake of making sure we're all talking the same thin your definition of 19th century ?

no offense meant but we all know that some people have issues with those terms.

the 19th century covers the years 1800-1899, please confirm that this is the period we talk here, thanks.
Title: Re: Magnitude of future warming
Post by: petm on July 05, 2019, 12:48:49 AM
6-10 C

IPCC is the best comprehensive summary of the current (very immature) science. Humans won't mitigate their behavior I think, so take RPC 8.5 as the initial guess. Add in known and unknown feedbacks that have been omitted, the conservative nature of science which has consistently underestimated effects, and the politicization of the IPCC report. Result is easily 6 C.
Title: Re: Magnitude of future warming
Post by: wolfpack513 on July 05, 2019, 12:56:55 AM
Re: Magnitude of future warming

can you for the sake of making sure we're all talking the same thin your definition of 19th century ?

no offense meant but we all know that some people have issues with those terms.

the 19th century covers the years 1800-1899, please confirm that this is the period we talk here, thanks.

Yes, Schurer et al. 2017 is specifically about underestimated 19th century warming.  The paper states that 1850-1899 warming may be underestimated by 0.1-0.2°C(mostly due to higher than normal volcanic activity).

If this is true then global mean temperature is closer to 1.3-1.4°C above preindustrial.  That would mean we’ve got 5-10 years until +1.5°C..
Title: Re: Magnitude of future warming
Post by: kassy on July 05, 2019, 02:53:42 PM
Funny thing is that we found the same for a more recent temperature set:

"The UK’s Met Office recently released “HadSST4”, the largest update since 2011 to its widely used sea surface temperature (SST) record.

The new version provides more accurate estimates of SSTs in the period during and after the second world war, as well as over the past decade. It suggests that the world’s oceans have warmed by around 0.1C more than previously thought since pre-industrial times.

Carbon Brief estimates that the revisions to the Hadley SST record would reduce the global “carbon budget” remaining to limit warming to 1.5C by between 24% and 33%, depending on how the budget is calculated.

This means that instead of having 9-13 years of current emissions before 1.5C is exceeded, the budget only has 6-10 years left.

https://www.carbonbrief.org/analysis-major-update-to-ocean-heat-record-could-shrink-1-5c-carbon-budget

Hat tip ASLR. He also writes: The linked article calculates that due to recent more accurate estimates of SSTs that the IPCC SR15's carbon budget to stay below a 1.5C GMSTA will be spent 3 to 5 years sooner that previously assumed by consensus climate scientists.  However, if climate sensitivity is higher than consensus climate scientists assume, then we may already spent all of our carbon budget and then some.
Title: Re: Magnitude of future warming
Post by: b_lumenkraft on July 05, 2019, 02:57:11 PM
Another nail in the coffin of the 'carbon budget' myth.
Title: Re: Magnitude of future warming
Post by: ArcticMelt2 on July 05, 2019, 05:32:21 PM
The current warming should be huge.

During the past interglacial period 130 thousand years ago, the temperature over 8 thousand years after the maximum of the Milankovich cycle fell by about 5 degrees:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.dandebat.dk%2Fimages%2F1517p.jpg&hash=e2c0316bae1ea2eaf7c45ccfaad708dc)

The development of agriculture over the past 8 thousand years with a minimum increase in the concentration of greenhouse gases (carbon dioxide and methane) has made it possible in fact to stabilize the temperature without multi-degree cooling.

If the development of agriculture allowed to increase the concentration of CO2 by 20 ppm, then today's industrial civilization did it at least 140 ppm.

This means that the contribution of industrial civilization to the present time is at least 7 times greater than the agricultural civilization.

In this regard, I think the final warming will be several tens of degrees.
Title: Re: Magnitude of future warming
Post by: magnamentis on July 05, 2019, 05:59:40 PM

In this regard, I think the final warming will be several tens of degrees.

30+(at least 2 tens to make it several) is 50C and since twice is more twice but several that wold make it at least 30C + 30C = 60C  / 40C + 30C = 70C ?

perhaps you reconsider such extreme statement.

i repeat that if anyone comes to read what we have to say and is reading obvious exaggerations he feels confirmed in his doubts and further spread the news that GW is a hoax.

credibility is everything ot make things happen fast, at the end what counts is are the facts and the real events but in case of prediction it is  "crime" to the cause to torbedize it with easily to falsify extreme exaggerations.

there is too much profiling and belonging to the winning group energy in this forum, best seen in the  electric car / tesla threads. black or white instead of thinking about the best and fastest and most sustainable solutions which ALWAYS will be a MIX.
Title: Re: Magnitude of future warming
Post by: ArcticMelt2 on July 05, 2019, 06:10:26 PM
Man, did you hear anything about feedbacks?

The main warming does not occur immediately, but over several decades, centuries, millennia. For example, the simulations say that Greenland will melt from one to ten thousand years.

The fact that the current warming will be huge directly says that the maximum of the past interglacial was sharp, while the current has a flat top. Why does Holocene have stable temperatures compared to Eem?

Or maybe you think Stephen Hawking is an idiot?

https://www.inverse.com/article/33729-stephen-hawking-trump-climate-change-venus-syndrome

Quote
“We are close to the tipping point where global warming becomes irreversible. Trump’s action could push the Earth over the brink, to become like Venus, with a temperature of two hundred and fifty degrees, and raining sulphuric acid,” he told BBC News.

“Climate change is one of the great dangers we face, and it’s one we can prevent if we act now,” he continued. “By denying the evidence for climate change, and pulling out of the Paris climate agreement, Donald Trump will cause avoidable environmental damage to our beautiful planet, endangering the natural world, for us and our children.”

Stephen Hawking is a man of few words, as the device that allows him to communicate limits him to about one per minute. When he does speak, the topic increasingly veers towards doomsday scenarios for humanity. Last year he said the substantial destruction of our species was a near certainty within 10,000 years, a prediction he has since revised to 1,000 and then to 500 years.

Hawking has offered several possible scenarios for the downfall of humans, but in his recent interview he refers specifically to the Venus syndrome, which supposes that if enough greenhouse gases enter Earth’s atmosphere there will be runaway global warming that will not stop until the planet is dead and dry.

In a sense, the Venus syndrome is Earth’s inevitable fate, barring some extraordinary event that pushes this planet out into a farther orbit. On a timescale of billions of years, the sun will grow brighter and hotter until the Earth can no longer let out as much energy as it takes in.

Title: Re: Magnitude of future warming
Post by: petm on July 05, 2019, 06:37:45 PM
Average surface warming above ~15 C (vs. pre-industrial) seems unlikely, since that would be hotter than at any time in the last 500 million years.

Anyways, it's somewhat moot since anything above ~4 C could make Earth uninhabitable and cause global ecosystem collapse, especially if that change occurs as quickly as by 2100. That would be many orders of magnitude faster than any previous warming event and leave not nearly enough time for ecosystems to migrate, let alone for species to adapt.

https://en.wikipedia.org/wiki/Geologic_temperature_record#Overall_view
https://skepticalscience.com/Can-animals-and-plants-adapt-to-global-warming.htm.
Title: Re: Magnitude of future warming
Post by: b_lumenkraft on July 05, 2019, 06:40:51 PM
Average surface warming above ~15 C seems unlikely, since that would be hotter than at any time in the last 500 million years.

Past Performance Is No Guarantee of Future Results
Title: Re: Magnitude of future warming
Post by: magnamentis on July 05, 2019, 07:03:20 PM
Average surface warming above ~15 C seems unlikely, since that would be hotter than at any time in the last 500 million years.

Past Performance Is No Guarantee of Future Results

yes but there are the laws of physics and even if it will be 19C it won't be several tens as he said. nothing to add to that read below what i have to say and that will be it.

and he said "unlikely" not impossble while this IS TOTALLY IMPOSSIBLE indeed
Title: Re: Magnitude of future warming
Post by: magnamentis on July 05, 2019, 07:04:15 PM
Man, did you hear anything about feedbacks?

don't get picky man, especially when you don't read and your reply has nothing to do with my point.

several tens of degrees, no matter how long, due to man made carbon emission, will not happen, it will happen once when the sun starts the process to become a red giant, even more then.

it will never be 80C (for example) at the equator due to man made global warming as we discuss it here and before this happen we really get extinct and the process will start to reverse upon next opportunity (negative feedback) lock at the curve during WW1 and WW2. if we say it's man made we can assume that the process slows down and eventually will reverse once we stop to contibute.
and at 60C air temps over large areas we will not be able to contribute, cooling will be impossible be it ICEs or nuclear power plants or anything, animals will day and stop farting etc. etc.

you are a pessimistic sensationalist who got hurt because i speak a clear language. poeple who only want to profile themselves, stick out, be right, belong to the winners, seek exitement etc. a larger part of the problem, hence of the causes the brought us to this point.

if only farmers and truckers drove trucks and if everyone would spend on ICE vehicles what he can buy instead of lease and borrow, the problem would be manifold smaller. most things are based on ego driven mechanisms and whether an extremist is a climate change denier, a inquisitor, a jihadist or a follower of any other extremist group, is a sheer coincidence hence for me all extremist are evil, dangerous and counterproductive.

as stephen, yes he was overrated. had he been a healthy, sporty and attractive man he never would have gotten the attention and since i study astrophysics myself for the last few years and
even have my own therries, i.e. about dark matter/energy (probably wrong but interesting LOL)

i'm much farther off my own fields of work and interest in this forum than from stephan's.

fame is only important for fanboys who need someone to follow ( cling to the skirts seem ) else it's often more of a disqualifications with a few exceptions who did not seek public fame but got it through their achievements and until now, that man either howled with the pack and where he did not not much of what he predicted has happened.

buzz words is a known term, buzz names less so haha... can't impress me with names, not at all.

last but not least this will be the last time we talk, no time and energy for this.

several tens of degrees due to carbon emission (manmade) what a joke.

and don't come with venus now, she's much closer to the sun and many other factors play a role but as i said, not longer in a mood for this useless task. KF it will be. so long.

Title: Re: Magnitude of future warming
Post by: petm on July 05, 2019, 07:18:18 PM
Past Performance Is No Guarantee of Future Results
Lol. Very true, which is why, as magnamentis pointed out, I said unlikely rather than saying impossible.

But gentle people, there's no need to argue. Even 10 C is far, far too much. Stay on target...
Title: Re: Magnitude of future warming
Post by: ArcticMelt2 on July 05, 2019, 08:28:32 PM
The fact that the current warming will be huge directly says that the maximum of the past interglacial was sharp, while the current has a flat top. Why does Holocene have stable temperatures compared to Eem?

On the same topic, an excellent review of 2016.

https://www.earthmagazine.org/article/comment-how-long-have-humans-been-altering-earths-climate

(https://www.earthmagazine.org/sites/earthmagazine.org/files/styles/full_width/public/2016-04/April_Comment_Ruddiman.png?itok=l3036eCl)

Quote
The early anthropogenic hypothesis holds that prolonged warmth in the Holocene was caused by early agriculture. Paleoclimatologists have long sought an analog of the current Holocene interglaciation. Here, precession (A) and obliquity (B), which impact solar insolation, and atmospheric carbon dioxide concentrations (C) of previous interglaciations are compared with the Holocene (stage 1). The closest analog to the Holocene is stage 19, which began about 787,000 years ago. Credit: Ruddiman et al., Review of Geophysics, 2016.

Quote
Throughout the 20th century the paleoclimate science community regarded the warmth of the current (Holocene) interglaciation — prior to the major anthropogenic intervention of the last 150 years — as overwhelmingly natural in origin. In this view, changes in Earth’s orbit had resulted in increased summer insolation at high latitudes of the Northern Hemisphere, which began melting the North American and Scandinavian ice sheets 17,000 years ago and eventually ushered in interglacial warmth. Although further orbital shifts then led summer insolation to begin decreasing 10,000 years ago, the drop was thought not to have been substantial enough to cause renewed glaciation.

In the “early anthropogenic hypothesis,” first published in 2003, I proposed a different interpretation: that greenhouse gas emissions from early agriculture were the main reason for prolonged warmth lasting into modern times. I noted that in three previous interglaciations observed in ice-core records, concentrations of both carbon dioxide and methane decreased through the first 10,000 years, resulting in cooling trends that led to renewed glaciation. But the equivalent part of the current interglaciation has been different: Carbon dioxide concentrations rose during the last 7,000 years, and methane concentrations rose during the last 5,000 years. I proposed that these anomalous greenhouse gas increases were anthropogenic in origin and kept global climate warmer than it would have been in a world controlled only by nature.

I attributed the anomalous rise in carbon dioxide since 7,000 years ago to early deforestation, and the rising methane trend since 5,000 years ago to the spread of rice irrigation and livestock tending. Back in 2003, quantitative information about early agriculture was scarce, except for one very interesting data point: The 1086 Domesday Book, a survey ordered by William the Conqueror, reported that forests covered just 15 percent of Britain, indicative of early deforestation, with forest cover already similar, in fact, to levels today.

The early anthropogenic hypothesis was received with acclaim by some scientists, but with deep skepticism by others. From 2004 to 2009, several prominent climate scientists published papers criticizing it. The most prevalent argument was that far too few people were living thousands of years ago to have caused land-use changes sufficient to alter greenhouse gas levels.

Another criticism centered on a previous interglaciation that was proposed as the closest orbital analog to the current interglacial — stage 11, which began about 424,000 years ago. That interglaciation was thought to have lasted 26,000 years, compared to just 11,000 years (to date) for the present one, suggesting that some 15,000 years of interglacial warmth potentially still remain ahead of us now before the next glaciation.

In addition, ratios of carbon-13 to carbon-12 in ice-core carbon dioxide, an index of net global terrestrial emissions, showed only a weak decrease since early in the current interglaciation. This implied very low deforestation emissions during the last 7,000 years, equivalent to an addition of just 2 to 3 parts per million (ppm) carbon dioxide to the atmosphere.

Since 2010, however, a surge of new evidence converging from a wide range of geoscience-related disciplines has refuted these criticisms and lent support to the early anthropogenic hypothesis. Surveys of historical records by ecological modeler Jed Kaplan, myself and landscape ecologist Erle Ellis found that farmers in both Europe and China 2,000 years ago used at least four times as much land per person as those in the centuries just before the industrial era (the 1700s). Early slash-and-burn farming practices that rotated from plot to plot were highly inefficient and cleared large amounts of land. In contrast, modern farmers plant one or more crops on the same land every year.

This evidence of early farmers clearing more land per capita suggests, for example, that the 200 million to 250 million people living 2,000 years ago were using an area of land for agriculture equivalent to that used by almost a billion people in more recent times. Based on this evidence, Kaplan ran a land-use simulation that found that preindustrial anthropogenic carbon dioxide emissions would have added 24 ppm to the atmospheric concentration, five times the amount estimated by modelers who had assumed that early farmers used relatively small amounts of land through the millennia.

Work by geologist and palynologist Chronis Tzedakis and others showed that interglacial stage 11 is not a good orbital analog for the current interglaciation after all. While both interglaciations were characterized by similar low-amplitude changes in the eccentricity-modulated precession of Earth’s orbit, the obliquity of the orbit during stage 11 was far offset from the one in the current interglaciation (see figure parts A and B).

The optimal orbital analog to the Holocene turns out to be interglacial stage 19, which began about 787,000 years ago. Comparison shows that the orbital indices of each are almost exactly in phase (see figure parts A and B). Yet, during the first 10,000 years of stage 19, atmospheric carbon dioxide concentrations fell steadily to between 240 and 245 ppm. This is identical to the range predicted by the early anthropogenic hypothesis (see figure part C) for a Holocene interglaciation free of an early anthropogenic overprint.

Archaeobotanist Dorian Fuller and his colleagues mapped the spread of irrigated rice across southern Asia from 5,000 to 1,000 years ago. He found that emissions from methane-producing rice paddies accounted for 70 parts per billion (ppb) out of the 100-ppb methane increase observed in ice cores during that interval. He also mapped the spread of methane-emitting livestock, but has not estimated their methane emissions.

Paleoecologists Ralph Fyfe, Jessie Woodbridge and Neil Roberts and their colleagues recently published results of a comprehensive synthesis of pollen data from hundreds of cores across north-central Europe. They showed that deforestation was nearly complete before the industrial era, as I had claimed in the early anthropogenic hypothesis. In Britain, deforestation was already extensive by 2,000 years ago, consistent with the evidence from the Domesday Book. No other continent has been analyzed in comparable detail, but planning for such studies is underway.

The problem of the weak carbon-13 isotopic signal turns out to have a plausible explanation also: a coincidental offsetting of the anthropogenic emissions by natural burial of carbon in boreal peats. Ecologist Zicheng Yu has shown that the amount of carbon stored in peats during the last 7,000 years is equivalent to a 21-ppm reduction of carbon dioxide in the atmosphere. Similar increases in carbon storage in peats during previous interglaciations must have contributed to the decreases in atmospheric carbon dioxide observed in ice cores at those times, with resulting cooling effects on climate. During the current interglaciation, however, anthropogenic emissions from deforestation offset that natural trend. The 24-ppm anthropogenic carbon dioxide release due to deforestation estimated by Kaplan slightly outweighs the 21-ppm carbon dioxide withdrawal Yu estimated for carbon burial in peats and satisfies the carbon-isotopic constraint.

Another factor in the global carbon budget of the last 7,000 years is carbon dioxide feedback from the ocean. Direct emissions of carbon dioxide from deforestation represent an anthropogenic anomaly compared to previous interglaciations. These emissions would have prevented both the atmosphere and oceans from cooling, keeping them anomalously warm.

Experiments by climate modelers John Kutzbach, Steve Vavrus and Feng He suggest whole-ocean warming of 0.8 to 0.9 degrees Celsius or more, sufficient to cause two kinds of feedbacks that would have released stored carbon dioxide from the oceans. Reduced carbon dioxide solubility in the warm ocean would have emitted 6 ppm or more carbon dioxide to the atmosphere. Additionally, anomalous warmth in the Southern Ocean would have reduced sea-ice cover and prompted carbon dioxide exchange with overlying air masses, again increasing carbon dioxide in the atmosphere. These feedbacks count as anthropogenic because they are the result of direct emissions from deforestation.

One indication of the expanding impact of the early anthropogenic hypothesis on the larger scientific community is the evolving agenda of the Past Global Changes (PAGES) program, a core project of the International Geosphere-Biosphere Program. In the 1980s, PAGES began a major initiative called the “2K” project, with the goal of measuring paleoclimatic responses during the last 2,000 years in order to construct a natural baseline against which to assess the anthropogenic effects of the last 150 years.

Last year, however, PAGES began a new effort called the “Land Cover 6K” project, motivated by the growing realization that humans have been altering land cover, greenhouse gas concentrations and global climate in a substantial way for at least 6,000 years.
Title: Re: Magnitude of future warming
Post by: kassy on July 06, 2019, 05:51:48 PM
In this regard, I think the final warming will be several tens of degrees.


This is far out of earths historical bounds:

During the PETM, the global mean temperature appears to have risen by as much as 5-8°C (9-14°F) to an average temperature as high as 73°F. (Again, today’s global average is shy of 60°F.)

*their inconsistent editing* Max was 23 C (22,77) current is 15,55 C.

The limit is set by incoming solar radiation. The greenhouse gasses keep outgoing radiation in and warm the planet that way. In the PETM there was no ice at the poles so 23C is about the max we can get until someone blows up the sun.

https://www.climate.gov/news-features/climate-qa/whats-hottest-earths-ever-been

PS: Speaking of that a freebie. It is not currently possible for Earth to reach a venus like atmosphere but we will get there. As the sun swells up at the end of its life it will become much warmer here. When ocean surface temperatures reach 66C the climate flips to a venus type one.

Title: Re: Magnitude of future warming
Post by: ArcticMelt2 on July 06, 2019, 06:32:22 PM
In this regard, I think the final warming will be several tens of degrees.


This is far out of earths historical bounds:

During the PETM, the global mean temperature appears to have risen by as much as 5-8°C (9-14°F) to an average temperature as high as 73°F. (Again, today’s global average is shy of 60°F.)

*their inconsistent editing* Max was 23 C (22,77) current is 15,55 C.

The limit is set by incoming solar radiation. The greenhouse gasses keep outgoing radiation in and warm the planet that way. In the PETM there was no ice at the poles so 23C is about the max we can get until someone blows up the sun.

https://www.climate.gov/news-features/climate-qa/whats-hottest-earths-ever-been

PS: Speaking of that a freebie. It is not currently possible for Earth to reach a venus like atmosphere but we will get there. As the sun swells up at the end of its life it will become much warmer here. When ocean surface temperatures reach 66C the climate flips to a venus type one.

Even during PEMT, the rate of increase in greenhouse gases was less by an order of magnitude:

https://desdemonadespair.net/2016/03/what-were-doing-to-earth-has-no.html

(https://lh3.googleusercontent.com/-yB9mWDm1H4s/VvWGQJqMH8I/AAAAAAAAfQI/-h5tbplKdrkDZZjVvmsXIB0WULAatLThACHM/image%255B1%255D?imgmax=800)

Compared with the past glacial periods, the difference reaches 100 times.

We are heating the planet with unprecedented speed in the geological history of the Earth. This will cause the unprecedented destruction of the biosphere, ice sheets and permafrost, destabilization of tectonic plates.
Title: Re: Magnitude of future warming
Post by: ArcticMelt2 on July 06, 2019, 07:28:37 PM
The limit is set by incoming solar radiation. The greenhouse gasses keep outgoing radiation in and warm the planet that way. In the PETM there was no ice at the poles so 23C is about the max we can get until someone blows up the sun.

https://www.climate.gov/news-features/climate-qa/whats-hottest-earths-ever-been

PS: Speaking of that a freebie. It is not currently possible for Earth to reach a venus like atmosphere but we will get there. As the sun swells up at the end of its life it will become much warmer here. When ocean surface temperatures reach 66C the climate flips to a venus type one.

In addition to ice there are huge reserves of carbon in the earth’s crust and biosphere:

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.ecobase21.net%2FLesmotsduclimatsmartphone%2Fimages%2FCycleducarbone.jpg&hash=d62351821f8fd720e8bef237c2b107d1)

(https://www.encyclopedie-environnement.org/app/uploads/2016/07/Tableau-1_Carbon-cycle_version-anglaise.png)

There is no limit for warming.
Title: Re: Magnitude of future warming
Post by: kassy on July 06, 2019, 10:19:26 PM
We know that.

I will repeat:

The limit is set by incoming solar radiation. The greenhouse gasses keep outgoing radiation in and warm the planet that way. In the PETM there was no ice at the poles so 23C is about the max we can get until someone blows up the sun.

All the other stuff is true but the important point is that we can reach into territory where feedbacks overwhelm any possible policy or tech dreams. This is the only point that matters.

Title: Re: Magnitude of future warming
Post by: wolfpack513 on July 08, 2019, 01:06:42 AM
This PETM occurred over 1000s of years so the comparison is silly.  We have a close handle on radiative forcing changes and we’re at 3.1 W/m² above preindustrial.  We’re not sniffing those numbers by 2100 even with some acceleration.  Emissions are going to drop off long before we get above 3°C due economic constraints. 
Title: Re: Magnitude of future warming
Post by: Tom_Mazanec on July 08, 2019, 02:13:50 PM
I thought they would drop off by now due to Peak Oil but I was wrong. Don't overestimate "economic constraints" or underestimate feedbacks. We could go well over three degrees.
Title: Re: Magnitude of future warming
Post by: vox_mundi on September 17, 2019, 12:30:11 PM
Earth to Warm More Quickly, New Climate Models Show
https://phys.org/news/2019-09-earth-quickly-climate.html

By 2100, average temperatures could rise 6.5 to 7.0 degrees Celsius above pre-industrial levels if carbon emissions continue unabated, separate models from two leading research centres in France showed.

... "With our two models, we see that the scenario known as SSP1 2.6—which normally allows us to stay under 2C—doesn't quite get us there," Olivier Boucher, head of the Institute Pierre Simon Laplace Climate Modelling Centre in Paris, told AFP.

A new generation of 30-odd climate models known collectively as CMIP6—including the two unveiled Tuesday—will underpin the IPCC's next major report in 2021.

A core finding of the new models is that increased levels of CO2 in the atmosphere will warm Earth's surface more easily than earlier calculations had suggested.

If confirmed, this higher "equilibrium climate sensitivity", or ECS, means humanity's carbon budget—our total emissions allowance—is likely to shrink.

Quote
... "Higher warming would allow less time to adapt and mean a greater likelihood of passing climate 'tipping points' such as thawing of permafrost, which would further accelerate warming."

The French models are among the first to be released, but others developed independently have come to the same unsettling conclusion, Boucher confirmed.

"The most respected ones—from the United States, and Britain's Met Office—also show a higher ECS" than the previous generation of models, he said.

-----------------------

2050 Is Too Late – We Must Drastically Cut Emissions Much Sooner
https://phys.org/news/2019-09-late-drastically-emissions-sooner.amp

(https://scx1.b-cdn.net/csz/news/800/2019/1-2050istoolat.jpg)

Four UK emissions pathways. (a) is based on our current rate of reduction, and (b) shows that linearly reducing emissions to net zero by 2050 means we’ll exhaust our carbon budget in four years. (c) shows that 2025 is the latest date we could linearly reduce our emissions to net zero, and (d) shows that for a 2050 target to stay within our budget, we’d need a 24% annual reduction in emissions.

The UK footprint has been falling slowly (at around 1.5% a year) since 2010. But if it continued to fall this slowly, the carbon budget would be exhausted by 2023, in just four years' time (Scenario a).

... What is notable about the 'Scenario c' pathway is that, within little more than a decade, carbon emissions must already have fallen to a very low level. With a 24% annual rate of reduction, UK emissions in 2030 would only be 22m tonnes—less than 5% of the current level of emissions. Only a small programme of negative emissions technologies would be needed to achieve net zero at this point.

Clearly the challenge is still colossal. A 24% reduction in emissions amounts to a cut of 140 million tonnes in the very first year alone. The UK has never achieved anything close to this since its carbon footprint was first measured in 1990. In 2009, when the economy was in recession, the carbon footprint fell by 80m tonnes, while its best post-crisis reduction saw a fall of only 38m tonnes in 2016.
Title: Re: Magnitude of future warming
Post by: vox_mundi on September 18, 2019, 10:37:37 PM
Uh-Oh ...

Study of Ancient Climate Suggests Future Warming Could Accelerate
https://phys.org/news/2019-09-ancient-climate-future.html
 
Researchers at the University of Michigan and the University of Arizona used a state-of-the-art climate model to successfully simulate—for the first time—the extreme warming of the Early Eocene Period, which is considered an analog for Earth's future climate.

They found that the rate of warming increased dramatically as carbon dioxide levels rose, a finding with far-reaching implications for Earth's future climate, the researchers report in a paper scheduled for publication Sept. 18 in the journal Science Advances.

Another way of stating this result is that the climate of the Early Eocene became increasingly sensitive to additional carbon dioxide as the planet warmed.

Quote
... "It is a scary finding because it indicates that the temperature response to an increase in carbon dioxide in the future might be larger than the response to the same increase in CO2 now. This is not good news for us."

The researchers determined that the large increase in climate sensitivity they observed—which had not been seen in previous attempts to simulate the Early Eocene using similar amounts of carbon dioxide—is likely due to an improved representation of cloud processes in the climate model they used, the Community Earth System Model version 1.2, or CESM1.2.

The same cloud processes responsible for increased climate sensitivity in the Eocene simulations are active today, according to the researchers.

... "For the first time, a climate model matches the geological evidence out of the box—that is, without deliberate tweaks made to the model. It's a breakthrough for our understanding of past warm climates," Tierney said.

... The current consensus among climate scientists is that the equilibrium climate sensitivity (ECS) is likely to be between 1.5 C and 4.5 C (2.7 F-8.1 F).

The equilibrium climate sensitivity in CESM1.2 is near the upper end of that consensus range at 4.2 C (7.7 F). The U-M-led study's Early Eocene simulations exhibited increasing equilibrium climate sensitivity with warming, suggesting an Eocene sensitivity of more than 6.6 C (11.9 F), much greater than the present-day value.

Open Access: J.Zhu, C.Poulsen, et.al. "Simulation of Eocene extreme warmth and high climate sensitivity through cloud feedbacks" (https://advances.sciencemag.org/content/5/9/eaax1874) Science Advances (2019).
Title: Re: Magnitude of future warming
Post by: Hefaistos on September 19, 2019, 07:48:17 AM
Referring to the previous two posts by Vox, i don't think they are too relevant for AGW.
It's unimaginable that we will get to 1000 ppm CO2 and a climate like in the Early Eocene  given:

1. the fast transition to renewable energy taking place. Capitalism already prefers renewables as they are less costly per energy unit, i.e. more profitable, than fossil fuels. This trend will only become stronger over the coming decades.
2. that we still are in an ice-age, i.e. the basic climate setup for coming millenia is unfavourable for an Early Eocene to develop.
3. that previous CMIP model generations (CMIP 3 and 5) have erred strongly, demonstrating too much warming compared to actual observations.

The time-scale involved for a transition to Early Eocene climate is millenia, and for such long period of time mankind will not only strongly scale back using fossil fuels, we will also start sucking CO2 back.
Thus, it would be irrelevant to use the high-end ECS values coming out of the climate models running Early Eocene climate.
The only thing that might refute this is if we get some strong, positive feedback mechanisms triggered in the coming decades.
Title: Re: Magnitude of future warming
Post by: KiwiGriff on September 19, 2019, 12:00:09 PM
CIMP3
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.realclimate.org%2Fimages%2Fcmp_cmip3_sat_ann-1-600x485.png&hash=66f65586c7090c2fd668acb127a74e25)
CIMP5
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.realclimate.org%2Fimages%2Fcmp_cmip5_sat_ann-2-600x484.png&hash=90af28e18b427972f38d1536b37473cd)
http://www.realclimate.org/index.php/climate-model-projections-compared-to-observations/
Annual average for 2019, eight months in, is now second behind 2016 and ahead of 2018 in third place. This year was  a very mild  El Niño or neutral depending on the metric you use.   We are presently above the mean of the model  runs in both cmip 3 and 5 .   The models have not erred at all let alone strongly.
 
1 Do you now the difference between  TCS, ECS and ESS ?
2 Climate = 30 years. Less than that you are looking at  internal variably "weather"  not the accuracy of "climate" models. The talk of a pause in warming  was based on the same idiocy.
3 The keeling curve is still a curve. We have not yet halted the acceleration in CO2 levels.
4 What has happened in the past has no relevance to what is happening now. Never has the earth experienced such a quick rise in CO2  .  ESS will take millenia  to resolve before we will really know. We may already have emitted enough to be outside of an ice age .
5. Relying on an as yet unknown future CCS  technology is magical thinking.

6 You should be banned from this forum for denial.
Title: Re: Magnitude of future warming
Post by: nanning on September 19, 2019, 12:04:44 PM
(KiwiGriff posted just before me but I have different points)

Sorry Hefaistos but I strongly disagree with your post.

You probably don't mean it like that but to me your list smells of soft denial.

1. If any progress has been made, it has accellerated the Keeling curve. The system of capitalism can't solve this. How long do you want GDP growth?
2. We are not in an iceage anymore. The increasing amount of GHG in the atmosphere prohibits that. We have changed the sensitive Earth systems. All the ice is going.
3. And here I was thinking that a lot of AGW related observations of reality suprise us time and again because they happen much sooner than expected. If I understand correctly, many more realistic CMIP6 models have a higher climate sensitivity i.e. are predicting even higher temperature increases.
Following the posts by ASLR in 'his' important science thread, I got the idea that the previous models were too conservative.


Imagination and science. I can imagine many feedbacks kicking in and powerful step-changes with or without an El Niño. Because the climate system will self-amplify and the anthropogenic influence will not be significant anymore.

Reading your last paragraph, I think you do have strong imagination. Just not the right kind.
Your very last sentence seems to contradict your second sentence.
Title: Re: Magnitude of future warming
Post by: Hefaistos on September 19, 2019, 01:59:43 PM
 
1 Do you now the difference between  TCS, ECS and ESS ?
Yes, i do, except for TCS. Maybe you can explain that one?

Quote
2 Climate = 30 years. Less than that you are looking at  internal variably "weather"  not the accuracy of "climate" models. The talk of a pause in warming  was based on the same idiocy.
I didn't bring up any 'pause in warming' as it is indeed idiocy. The oceans are continously warming, as more than 90% of warming goes there, whereas the atmosphere has more variability.
You attached two graphs showing how CMIP models perform. The first one is not so relevant as it shows the older CMIP3 models. It's absolutely critical to evaluate the models' accuracy to forecast climate, as these models are the foundation for climate mitigation scenarios and climate policy making..
The attached graph compares observations of global temperature with CMIP5 simulations assessed by the IPCC 5th Assessment Report. The figure is an updated version of Figure 11.25a from IPCC AR5 which was originally produced in mid-2013.
The graph shows the raw ‘spaghetti’ projections of the 90 or so models used, with different observational datasets in black.
Observations are clearly on the lower side of the projections. Could there be something wrong with how the models handle forcings? Yes, there could. I will not go into that interesting off-topic further here.
Graph is from: https://www.climate-lab-book.ac.uk/comparing-cmip5-observations/

Quote
3 The keeling curve is still a curve. We have not yet halted the acceleration in CO2 levels.
True, but we're getting there. FF are being phased out, and the out-phasing will only get stronger in the coming two decades.

Quote
4 What has happened in the past has no relevance to what is happening now. Never has the earth experienced such a quick rise in CO2  .  ESS will take millenia  to resolve before we will really know. We may already have emitted enough to be outside of an ice age .
I think you should read the wikipedia pages on ice age. We are currently in an ace age called the Quaternary glaciation, it has lasted 2.58 million years. To claim that "we have emitted enough to be outside of an ice age" is a collossal statement. We have emitted for some 150 years, and we can de-emit in the coming centuries.
https://en.wikipedia.org/wiki/Ice_age
https://en.wikipedia.org/wiki/Quaternary_glaciation

Quote
5. Relying on an as yet unknown future CCS  technology is magical thinking.
There is nothing magic with CCS technology, as there are already several viable techniques being developed and deployed as full scale experimental facilities. CCS can be applied, and it will be applied. That's what IPCC says in AR5. You think that IPCC also divulge in 'magical thinking'? Carbon capture and storage (CCS) is necessary in almost all scenarios to mitigate climate change.
You should expect this to be part of the mitigation scenarios also in forthcoming AR6 (the WG8 group).
https://www.ipcc.ch/report/carbon-dioxide-capture-and-storage/
If mankind was able to emit x Gtonnes of CO2 during 100 years, we are fully capable of sucking all that CO2 back. Just apply the right economic incentives and let the market forces work. In the same way that renewables are now beating FF in terms of cost/kWh. Why did that actually happen? Because there are very strong incentives to develop new technology in the energy sector, and because capitalist market forces rule the world. Like it or dislike it, but those are the facts.

Quote
6 You should be banned from this forum for denial.
I'm grateful to all in this forum for their valuable contributions, even from high priests wanting to ban me. I'm here primarily to learn, and I have learnt a lot over the years of lurking.
I'm not in denial regarding AGW or the urgency regarding climate action, but I'm not an alarmist.
That said, I am in denial of some things:
I deny that we will 'ever' (10^5 years) be in an equable climate such as the Early Eocene.
I deny that GCM models are capable of forecasting our future climate, except for what is factual linearizations. I have said some things regarding that in the thread on "Validation of GCM models".
I'm sceptical of using GCM models for policy making, as they have crappy inputs, and also lack vital theory. I'm of course talking here about the strongest GHG of them all - water vapor.
Title: Re: Magnitude of future warming
Post by: Hefaistos on September 19, 2019, 02:35:06 PM
(KiwiGriff posted just before me but I have different points)

Sorry Hefaistos but I strongly disagree with your post.

You probably don't mean it like that but to me your list smells of soft denial.

1. If any progress has been made, it has accellerated the Keeling curve. The system of capitalism can't solve this. How long do you want GDP growth?
Nanning, I hope I answered most of your points in my answer to KiwiG, so I'll keep this brief.
Yes, capitalism can indeed solve this. The prime example is the incredible breakthrough, and  ongoing victory of renewables, as we speak.
I'm no friend of growth and i loathe materialism and consumerism, but i'm also a realist. But we can't just dream up a world where there is no growth and no capitalism and hope that this dream will solve our problems with AGW. Climate mitigation has to be built on realistic concepts, market forces and capitalist incentives.

Quote
2. We are not in an iceage anymore. The increasing amount of GHG in the atmosphere prohibits that. We have changed the sensitive Earth systems. All the ice is going.
Sure, if nothing is done all the ice will be going. However, the time scale is millennia. Capitalist mankind will not let it happen. I'm sure there will be many problems with the consequenses of AGW but we haven't passed any no-reversal tipping points yet. Read AR5 from IPCC.

Quote
3. And here I was thinking that a lot of AGW related observations of reality suprise us time and again because they happen much sooner than expected. If I understand correctly, many more realistic CMIP6 models have a higher climate sensitivity i.e. are predicting even higher temperature increases.
Following the posts by ASLR in 'his' important science thread, I got the idea that the previous models were too conservative.

see my reply to KiwiG regarding the GCM models, as the follow up of the performance of these models show the opposite.

Quote
Imagination and science. I can imagine many feedbacks kicking in and powerful step-changes with or without an El Niño. Because the climate system will self-amplify and the anthropogenic influence will not be significant anymore.

Reading your last paragraph, I think you do have strong imagination. Just not the right kind.
Your very last sentence seems to contradict your second sentence.
The climate system will certainly not self-amplify and run out of control on a time-scale of decades, and the anthropogenic influence will certainly not be made insignificant. No serious climate scientists believe that, and the IPCC provides us with mitigation scenarios. If they are realistic or not can and will be discussed. But we should never discount capitalist mankind's capacity for problem-solving technological innovation and implementation.


Title: Re: Magnitude of future warming
Post by: Klondike Kat on September 19, 2019, 02:53:40 PM
CIMP3
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.realclimate.org%2Fimages%2Fcmp_cmip3_sat_ann-1-600x485.png&hash=66f65586c7090c2fd668acb127a74e25)
CIMP5
(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.realclimate.org%2Fimages%2Fcmp_cmip5_sat_ann-2-600x484.png&hash=90af28e18b427972f38d1536b37473cd)
http://www.realclimate.org/index.php/climate-model-projections-compared-to-observations/
Annual average for 2019, eight months in, is now second behind 2016 and ahead of 2018 in third place. This year was  a very mild  El Niño or neutral depending on the metric you use.   We are presently above the mean of the model  runs in both cmip 3 and 5 .   The models have not erred at all let alone strongly.

That said, CMIP 3 does not appear to have erred.  Over the past 18 years, 7 years have occurred very near the model ensemble (split above and below), while 3 have had all four datasets above and 8 have had all four below.

CMIP 5 does not do as well.  13 of the 14 years show all four datasets below the ensemble, with only year near the ensemble mean (2016).  No years had all four datasets above.  Four years were very close to being outside the 95% spread.

Do you know the differense between the two (outside of CMIP5 yielding 0.1C higher temperature projection by 2020?
Title: Re: Magnitude of future warming
Post by: nanning on September 19, 2019, 05:10:41 PM
Referring to the previous two posts by Vox, i don't think they are too relevant for AGW.
It's unimaginable that we will get to 1000 ppm CO2 and a climate like in the Early Eocene  given:

This is not true. It is certainly imaginable. It has happened before. We are on that path. We make that path now.

Quote
1. the fast transition to renewable energy taking place. Capitalism already prefers renewables as they are less costly per energy unit, i.e. more profitable, than fossil fuels. This trend will only become stronger over the coming decades.

'Capitalism' is of course not an entity but I understand you. Renewables are very global resource hungry. Have you thought that out long term in a catastrophicly changing human world? You need those mines, those pockmarks in the Earth. Will there be poor local children and other poor people digging up your resources in very nasty conditions? OK not all mines are like that but I'm certain the indiginous people of the Amazone have something to add.
Neo-liberalism for 40 years means that most social functions are gone. It means foodbanks in a lot of rich countries. How long must that go on, expanding? Invariably, GDP growth means growth in foodbank use. The rich getting richer and the poor getting poorer. Also in rich countries. How does capitalism solve that? I am poor and I am also an inhibitant of a rich country and see all utilities degrading and everything getting more expensive and of lower quality.

Quote
2. that we still are in an ice-age, i.e. the basic climate setup for coming millenia is unfavourable for an Early Eocene to develop.

We are NOT in the basic climate setup!

Quote
3. that previous CMIP model generations (CMIP 3 and 5) have erred strongly, demonstrating too much warming compared to actual observations.

This really is a very strange and denier-like remark.

Quote
The time-scale involved for a transition to Early Eocene climate is millenia, and for such long period of time mankind will not only strongly scale back using fossil fuels, we will also start sucking CO2 back.
Thus, it would be irrelevant to use the high-end ECS values coming out of the climate models running Early Eocene climate.

You are a dreamer if you think technology and 'progress' will solve Earths energy imbalance and ecosystem collapses and mass extinction and the all abundant microplastic and ... etc.
Life of many humans on Earth are in danger and you think driving a Tesla car or having solar panels will solve their problems? Do you think e.g. African people are important?

Quote
The only thing that might refute this is if we get some strong, positive feedback mechanisms triggered in the coming decades.

There you go. Use that to stretch your imagination. You can do it :). No, it is not certain that it is far away in the future.
Title: Re: Magnitude of future warming
Post by: wili on September 19, 2019, 05:24:35 PM
H wrote: "It's unimaginable..." Your ability or inability to imagine something has, of course, no bearing on whether it is true. Try to avoid common fallacies: https://rationalwiki.org/wiki/Argument_from_incredulity

H wrote: " Capitalist mankind will not let it happen."

WTF?
Title: Re: Magnitude of future warming
Post by: El Cid on September 19, 2019, 05:36:10 PM

H wrote: " Capitalist mankind will not let it happen."

WTF?
It means that if your best personal interest is to solve a problem then you will work very very hard on it and you will likely get a solution. Self-interest drives man. That drives is very basic. That drive created capitalism and technological progress starting from the first stone-axes or before
Title: Re: Magnitude of future warming
Post by: wili on September 19, 2019, 05:54:30 PM
How's that been workin' for ya?

Since the 'triumph' of global capitalism some 40 years ago, general consumption and ff burning have accelerated greatly. All to the detriment of the planet and its/our future.

Individuals tend to make self-interested decisions generally based on the short term.

And of course mega-corporations' decisions tend to be even more short term, and they do everything they can to convince individuals to keep their decision making very, very short term.

To paraphrase James Lovelock: Leaving the health of the globe to capitalism is like leaving the care of a garden to goats. 
Title: Re: Magnitude of future warming
Post by: KiwiGriff on September 19, 2019, 06:19:48 PM
Klondike Kat
Look at the forcing adjusted result not the original projection  for cimp5 .
Climate models are not designed to be  economic models or project future solar activity.
Title: Re: Magnitude of future warming
Post by: Klondike Kat on September 19, 2019, 06:47:37 PM
Klondike Kat
Look at the forcing adjusted result not the original projection  for cimp5 .
Climate models are not designed to be  economic models or project future solar activity.

That improves the models slightly.
Title: Re: Magnitude of future warming
Post by: sidd on September 19, 2019, 10:56:11 PM
Re: ice age

we are well above the highest CO2 concentration over the last 3 million years (160-280 ppm)

sidd
Title: Re: Magnitude of future warming
Post by: sidd on September 19, 2019, 11:52:42 PM
I should add that even if we cut emissions to zero today, we have suppressed not just the next glaciation bu the next two.

As for large scale carbon sequestration, we have to sequester for geological time, at least on the order of  hundreds of millennia.  So I'll believe it when the first few dozen million tons  gets sequestered into long lived geological repository.  Together with funding mechanisms for loooong term monitoring. What those mechanisms might be, i have no idea, considering that the oldest continuously extant human organization is the Vatican at 2Kyr or so.

I do not expect to see that in my lifetime, although that's probably because i'm an old cynic.

sidd
Title: Re: Magnitude of future warming
Post by: sidd on September 20, 2019, 12:06:42 AM
I continue the sequestration/drawdown discussion in the "Direct Air Capture" thread

https://forum.arctic-sea-ice.net/index.php/topic,2484.msg229552.html#msg229552

sidd
Title: Re: Magnitude of future warming
Post by: be cause on September 20, 2019, 01:50:55 AM
 .. definately between 2 and 10'C . And I doubt I'll be here to be declared a winner of the world's most depressing poll .. :) .. b.c.
Title: Re: Magnitude of future warming
Post by: nukefix on September 20, 2019, 11:25:41 AM
I should add that even if we cut emissions to zero today, we have suppressed not just the next glaciation bu the next two.
How is that possible if CO2 sticks around only a few centuries?
Title: Re: Magnitude of future warming
Post by: kassy on September 20, 2019, 11:59:52 AM
4. Summary
[19] The carbon cycle of the biosphere will take a long
time to completely neutralize and sequester anthropogenic
CO2. We show a wide range of model forecasts of this
effect. For the best guess cases, which include air/seawater,
CaCO3, and silicate weathering equilibria as affected by an
ocean temperature feedback, we expect that 17– 33% of
the fossil fuel carbon will still reside in the atmosphere
1 kyr from now, decreasing to 10– 15% at 10 kyr, and 7%
at 100 kyr. The mean lifetime of fossil fuel CO2 is about
30– 35 kyr.
[20] A mean atmospheric lifetime of order 104 years is in
start contrast with the ‘‘popular’’ perception of several
hundred year lifetime for atmospheric CO2. In fairness, if
the fate of anthropogenic carbon must be boiled down into a
single number for popular discussion, then 300 years is a
sensible number to choose, because it captures the behavior
of the majority of the carbon. A single exponential decay of
300 years is arguably a better approximation than a single
exponential decay of 30,000 years, if one is forced to
choose. However, the 300 year simplification misses the
immense longevity of the tail on the CO2 lifetime, and
hence its interaction with major ice sheets, ocean methane
clathrate deposits, and future glacial/interglacial cycles. One
could sensibly argue that public discussion should focus on
a time frame within which we live our lives, rather than
concern ourselves with climate impacts tens of thousands of
years in the future. On the other hand, the 10 kyr lifetime of
nuclear waste seems quite relevant to public perception
of nuclear energy decisions today. A better approximation
of the lifetime of fossil fuel CO2 for public discussion might
be ‘‘300 years, plus 25% that lasts forever.’


http://geosci.uchicago.edu/~archer/reprints/archer.2005.fate_co2.pdf

So it does not.
Title: Re: Magnitude of future warming
Post by: nanning on September 20, 2019, 04:17:45 PM
"Atmospheric Lifetime of Fossil Fuel Carbon Dioxide"

https://www.researchgate.net/publication/38136820_Atmospheric_Lifetime_of_Fossil_Fuel_Carbon_Dioxide
DOI: 10.1146/annurev.earth.031208.100206

Quote
Abstract
CO2 released from combustion of fossil fuels equilibrates among the various carbon reservoirs of the atmosphere, the ocean, and the terrestrial biosphere on timescales of a few centuries. However, a sizeable fraction of the CO2 remains in the atmosphere, awaiting a return to the solid earth by much slower weathering processes and deposition of CaCO3. Common measures of the atmospheric lifetime of CO2, including the e-folding time scale, disregard the long tail. Its neglect in the calculation of global warming potentials leads many to underestimate the longevity of anthropogenic global warming. Here, we review the past literature on the atmospheric lifetime of fossil fuel CO2 and its impact on climate, and we present initial results from a model intercomparison project on this topic. The models agree that 20–35% of the CO2 remains in the atmosphere after equilibration with the ocean (2–20 centuries). Neutralization by CaCO3 draws the airborne fraction down further on timescales of 3 to 7 kyr.
Title: Re: Magnitude of future warming
Post by: vox_mundi on September 20, 2019, 05:21:49 PM
Climate Change Takes Toll On Oceans, Ice: UN Report
https://phys.org/news/2019-09-climate-toll-oceans-ice_1_2.html

Loading the atmosphere with CO2 and greenhouse gases has spawned a host of consequences, starting with irreversible sea-level rise, according to a draft Intergovernmental Panel on Climate Change (IPCC) Special Report obtained by AFP.

Here are impacts highlighted in a summary slated for release on September 25:

...EL NINOS: Extreme El Ninos—weather phenomena which drive forest fires, cause disease outbreaks and affect cyclones—are expected to double in frequency if emissions are not cut.

SUSTENANCE: Food supply from shallow tropical waters could decline by 40 percent by the year 2100 because of warming and acidification.

SEA LEVEL: Compared to the 1980-2000 period, seas will rise nearly half a metre by 2100 if Earth warms 2C above preindustrial levels, and 84 cm in a 3C-4C world. In the 22nd century, the pace of sea-level rise is likely to jump 100-fold from 3.6 millimetres per year today to several centimetres annually.

Even if global warming is capped at 2C, oceans will eventually rise several metres, submerging areas that are today home to 280 million people.

FLOOD DAMAGE: Without major adaptation efforts, the cost of annual flood damage caused by storm surges would increase 100- to 1,000-fold by 2100.

NEW NORMAL: Many low-lying megacities and small island states will experience what are today rare sea-level extremes every year by 2050, no matter how fast CO2 emissions are drawn down.

WETLANDS: Globally, 20 to 90 percent of coastal wetlands will disappear by 2100, depending on sea-level rises.

OXYGEN: The concentration of life-giving oxygen in marine environments has dropped two percent in 60 years, and will decline another three to four percent by 2100 at current rates of carbon pollution. Oxygen levels will likely decline over 59-80 percent of the ocean surface within 20 years.

CORALS: Coral reefs—a major bulwark against storm surges—will decline by 90 percent even in a 1.5 C world. Two degrees would be a death sentence for corals, which underpin the livelihoods of half a billion people today.

GLACIERS: Average annual runoff from glaciers in most mountain regions will have peaked and begun to decline by 2100. Worldwide, more than two billion people today depend on glaciers for fresh water.

PERMAFROST: Thirty to 99 percent of the world's top-layer permafrost—the top three metres—could melt by 2100 if carbon pollution continues unabated, releasing a carbon bomb of greenhouse gases. If emissions are aggressively capped, the area thawed could be vastly reduced.

and many others ...

https://www.ipcc.ch/report/srocc/
Title: Re: Magnitude of future warming
Post by: Klondike Kat on September 20, 2019, 05:45:32 PM
Some fractino of carbon dioxide will remain in the atmosphere for centuries, perhaps millenia.

https://www.yaleclimateconnections.org/2010/12/common-climate-misconceptions-atmospheric-carbon-dioxide/

However, the atmospheric concentration is a function of both the amount present and the amount emitted.  Should emissions cease tomorrow (bear with me for a bit), atmospheric concentrations would begin to decline, rapidly at first, until they reach about ~25% of emitted levels.  This approximate value is consistent among all three previous references.  That equates to about 314 ppm after a century (280 ppm + 25% * (415 ppm - 280 ppm).  Hence, global temperatures would begin to fall shortly after atmospheric CO2 levels begin falling.

Obviously, emissions will not cease tomorrow.  They do not need to, in order to stabilize atmospheric concentrations at current conditions.  While the last 25% of emissions takes centuries to be removed, the first 25% is fast, taking about one decade.  Estimates vary widely, but an emissions reduction of about 40% would stabilize concentrations at current levels. 

Title: Re: Magnitude of future warming
Post by: mitch on September 20, 2019, 08:15:45 PM
There is an interesting paper in Science Advances:
https://advances.sciencemag.org/content/5/9/eaax1874

That is able to use new models to model the Paleocene-Eocene thermal maximum.  They were able for the first time to get the response observed by paleoclimate data with the estimated atmospheric CO2 at the time. There is an increased equilibrium climate sensitivity with warming, caused by changes in cloud physics.

Unfortunately, if correct, it predicts an ECS of 4.2 deg C for a doubling from pre-industrial CO2. It doesn't seem to be paywalled.

Title: Re: Magnitude of future warming
Post by: vox_mundi on September 20, 2019, 08:48:42 PM
^
See also: https://forum.arctic-sea-ice.net/index.php/topic,2715.msg229346.html#msg229346
Title: Re: Magnitude of future warming
Post by: oren on September 22, 2019, 02:01:20 PM
However, the atmospheric concentration is a function of both the amount present and the amount emitted.  Should emissions cease tomorrow (bear with me for a bit), atmospheric concentrations would begin to decline, rapidly at first, until they reach about ~25% of emitted levels.  This approximate value is consistent among all three previous references.  That equates to about 314 ppm after a century (280 ppm + 25% * (415 ppm - 280 ppm).  Hence, global temperatures would begin to fall shortly after atmospheric CO2 levels begin falling.
I have no direct expertise here but I suspect the math is not proper. 415 does not represent the emitted amount, but the amount remaining after some equilibration with the ocean. So you are double-counting the equilibration.
Title: Re: Magnitude of future warming
Post by: gerontocrat on September 22, 2019, 08:32:59 PM
Some fractino of carbon dioxide will remain in the atmosphere for centuries, perhaps millenia.

https://www.yaleclimateconnections.org/2010/12/common-climate-misconceptions-atmospheric-carbon-dioxide/

However, the atmospheric concentration is a function of both the amount present and the amount emitted.  Should emissions cease tomorrow (bear with me for a bit), atmospheric concentrations would begin to decline, rapidly at first, until they reach about ~25% of emitted levels.  This approximate value is consistent among all three previous references.  That equates to about 314 ppm after a century (280 ppm + 25% * (415 ppm - 280 ppm).  Hence, global temperatures would begin to fall shortly after atmospheric CO2 levels begin falling.

Obviously, emissions will not cease tomorrow.  They do not need to, in order to stabilize atmospheric concentrations at current conditions.  While the last 25% of emissions takes centuries to be removed, the first 25% is fast, taking about one decade.  Estimates vary widely, but an emissions reduction of about 40% would stabilize concentrations at current levels.
I thought some arithmetic was in order, starting with

While the last 25% of emissions takes centuries to be removed, the first 25% is fast, taking about one decade.

415 ppm = a bit above 3,200 GT of atmospheric CO2.
280 ppm = a bit below 2,200 GT of atmospheric CO2.

Addition by us = circa 1,050 GT
25% of that     = 260 GT (1st decade loss)
which equates to 26 GT per annum

Current sequestration by the sinks is estimated at 55% of emissions at round 36GT = 20 GT per annum

(If that 1st decade applied to the total CO2 in the atmosphere,
we are talking about over 80 GT per annum sequestration required)
_______________________________________________________
Estimates vary widely, but an emissions reduction of about 40% would stabilize concentrations at current levels.

I made a little spreadsheet, assuming a quick reduction in emissions of 40% by 2030. The answer is IFF (if and only if) total sequestration stayed at (or above) current levels in GT, by 2030 CO2 ppm would start to fall, i.e. Klondike Kat's statement shown to be correct

BUT this defies history. Since the Keeling curve started, the data shows net addition to atmospheric CO2 at just below half of CO2 emissions. All the science says that the oceans are circa 30%, the land-based sinks circa 25% of that total sequestration of circa 55% of emissions.

The table shows that as emissions rose, sequestration by the sinks rose.
Data in GT        Emissions   Sequestration by the Sinks
1970s             17.14              9.60
1980s             20.01            12.60
2010’s             35.34            18.02

Qu:- If emissions fall, why should sequestration by the sinks stay up?

If sequestration as emissions fall mirrors sequestration as emissions increase, all that happens is that ppm increases slow.

I admit to being confused with little confidence in the attached graphs.
Title: Re: Magnitude of future warming
Post by: Klondike Kat on September 23, 2019, 07:03:18 PM
Current sequestration is not based on emitted amounts, but on atmospheric concentrations.  As concentrations continue to increase, sequestration should increase to keep pace (similar percentage).  At some point removal will equal addition, such that the conentration will remain constant.  Once emissions fall below the removal rate, atmospheric concentrations will fall.
Title: Re: Magnitude of future warming
Post by: oren on September 23, 2019, 08:35:45 PM
Again, I am far from knowledgeable on this subject, but I would guess sequestration is also dependent on ocean CO2 level, which has probably risen since the 1970s. Hope someone with more credentials can pitch in.
Title: Re: Magnitude of future warming
Post by: oren on September 23, 2019, 08:43:07 PM
Google to the rescue.

Quote
How the oceans absorb carbon dioxide is critical for predicting climate change
Air-sea gas exchange is a physio-chemical process, primarily controlled by the air-sea difference in gas concentrations and the exchange coefficient, which determines how quickly a molecule of gas can move across the ocean-atmosphere boundary. It takes about one year to equilibrate CO2 in the surface ocean with atmospheric CO2, so it is not unusual to observe large air-sea differences in CO2 concentrations. Most of the differences are caused by variability in the oceans due to biology and ocean circulation. The oceans contain a very large reservoir of carbon that can be exchanged with the atmosphere because the CO2 reacts with water to form carbonic acid and its dissociation products. As atmospheric CO2 increases, the interaction with the surface ocean will change the chemistry of the seawater resulting in ocean acidification.

Evidence suggests that the past and current ocean uptake of human-derived (anthropogenic) CO2 is primarily a physical response to rising atmospheric CO2 concentrations. Whenever the partial pressure of a gas is increased in the atmosphere over a body of water, the gas will diffuse into that water until the partial pressures across the air-water interface are equilibrated. However, because the global carbon cycle is intimately embedded in the physical climate system there exist several feedback loops between the two systems. For example, increasing CO2 modifies the climate which in turn impacts ocean circulation and therefore ocean CO2 uptake. Changes in marine ecosystems resulting from rising CO2 and/or changing climate can also result in changes in air-sea CO2 exchange. These feedbacks can change the role of the oceans in taking up atmospheric CO2 making it very difficult to predict how the ocean carbon cycle will operate in the future.
https://www.pmel.noaa.gov/co2/story/Ocean+Carbon+Uptake (https://www.pmel.noaa.gov/co2/story/Ocean+Carbon+Uptake)

Quote
Ocean Acidification: The Other Carbon Dioxide Problem
Fundamental changes in seawater chemistry are occurring throughout the world's oceans. Since the beginning of the industrial revolution, the release of carbon dioxide (CO2) from humankind's industrial and agricultural activities has increased the amount of CO2 in the atmosphere. The ocean absorbs about a quarter of the CO2 we release into the atmosphere every year, so as atmospheric CO2 levels increase, so do the levels in the ocean. Initially, many scientists focused on the benefits of the ocean removing this greenhouse gas from the atmosphere.  However, decades of ocean observations now show that there is also a downside — the CO2 absorbed by the ocean is changing the chemistry of the seawater, a process called OCEAN ACIDIFICATION.
https://www.pmel.noaa.gov/co2/story/Ocean+Acidification (https://www.pmel.noaa.gov/co2/story/Ocean+Acidification)

(https://www.pmel.noaa.gov/co2/files/co2_time_series_aloha_06-11-2019_med.jpg)
Title: Re: Magnitude of future warming
Post by: Florifulgurator on September 23, 2019, 08:51:25 PM
I would guess sequestration is also dependent on ocean CO2 level.
Yes. The other elephant in the room.
Like with thermal inertia there is also CO2 mixing inertia of oceans. Carbon sequestration is a job for centuries.
Title: Re: Magnitude of future warming
Post by: Klondike Kat on September 23, 2019, 09:33:49 PM
Again, I am far from knowledgeable on this subject, but I would guess sequestration is also dependent on ocean CO2 level, which has probably risen since the 1970s. Hope someone with more credentials can pitch in.

The sequestering is dependent on the partial pressure of the gas in the atmosphere and dissolved in the ocean.  Carbon dioxide in the atmosphere and dissolved in the ocean will strive to maintain equilibrium.  A change in one will lead to a change in the other.  Much of the gas that has been emitted into the atmosphere has already dissolved into the ocean.  This process with continue towards equilibrium.
Title: Re: Magnitude of future warming
Post by: oren on September 23, 2019, 10:37:35 PM
KK, I know that you strive hard to prove that things are better than they seem, a commendable goal when sincere, but I feel that in this case you are wrong. As the CO2 is equilibrated into the ocean, its rate of oceanic uptake slows down, in opposition to the way you describe it and to the math you presented above.
Title: Re: Magnitude of future warming
Post by: Klondike Kat on September 23, 2019, 11:00:57 PM
Oren, that would be the case if the equilibrium was fast and the atmospheric lifetime of CO2 was short.  These calculations are based on the premise that the lifetime is long, and the equilibrium is slow.  I am not the expert on the atmospheric lifetime of CO2, but am using the conclusions of others.  However, if the premise of a long lifetime is correct, then the ocean will continue to sequester CO2 for quite some time.  I am a chemist, not a biologist, so I cannot comment as readily about terrestrial sequestration.
Title: Re: Magnitude of future warming
Post by: sidd on September 24, 2019, 06:20:41 AM
It is true that ocean surface water will sequester CO2 at a rate proportional to difference of CO2 partial pressure between atmosphere and surface ocean.  Absent anything else, this rate will slow down as the difference goes to zero.

But ofcourse there are many,many anything elses. Carbonate equilibrium is one. Coccolithophores are another. The latter will dwindle as pH goes up reducing deep ocen sequestration. That's just one of the million feedbacks we are beginning to understand.

So i am not sanguine that the land and ocean sequestration we see today will continue. I am concerned about land sinks even more than ocean. It is increasingly clear that land sinks may easily turn into sources.

At present, half our fossil C emissions are sequestered by "natural" processes. If those take a hit, keeling curve will go up faster, as will radiative imbalance, warming and ecosystem impact.

sidd

Title: Re: Magnitude of future warming
Post by: Klondike Kat on September 24, 2019, 01:22:33 PM
Land and ocean sequestrations that are based on physical properties will not change as CO2 concentrations rise.  This is straight-forward chemistry.  These natural processes will not change.  The one process that may change is the biological sequestration.  Deforestation has added significantly to the increase in atmospheric carbon dioxide levels.  Fortunately, this has been recognized and efforts have been made to restore the forests (for habitat restoration purposes also).  This has fared much better than efforts to reduce carbon dioxide emissions. 

In the U.S., 26% of the forests were cut down by 1910 - mostly for agriculture.  Since then, the forested area has increased slightly (about 2%).  Europe has had much higher levels of deforestation, with some estimates at ~90%.  In recent years, thes temporal forests have been making a comeback, with reforestation efforts increasnig forested lands in both Europe and Asia.  Unfortunately, trends in tropical Africa and South America have countered these efforts.  Still, there is hope in reforestation efforts, which would increase land sequestration of carbon dioxide.  Hence, it seems more likely that sinks would increase in the coming years, rather than decrease.

https://ourworldindata.org/forests
Title: Re: Magnitude of future warming
Post by: gerontocrat on September 24, 2019, 02:17:54 PM
Future of land & ocean sinks

Everything changes all the time. Nothing is constant.

Below is some data about recent changes in the Southern Ocean uptake of CO2, currently increasing but for how long?

Elsewhere I found and lost a paper on that Ocean sinks work in 2 ways, on the chemical process discussed below, and biological processes - mostly by small organisms - e.g. algae. Photosynthesis traps carbon, organisms die, carbon trapped in the ocean floor sediments. Mankind is not being kind to life in the oceans.

As for the land sinks, planting trees by one part of mankind, destroying forests by another. Permafrost? Tundra?

Who knows what the net effect of all these changes will be.

__________________________________________________________
https://www.carbonbrief.org/scientists-solve-ocean-carbon-sink-puzzle

Scientists solve ocean ‘carbon sink’ puzzle

Quote
A new study, published in Nature, finds that recent changes in circulation patterns in the world’s oceans are playing a key role in how much CO2 they take up.

Weakening circulation patterns have boosted how much CO2 the oceans absorb since the 2000s, the researchers say, but there’s no guarantee that this will continue into the future.
 


the amount of CO2 that the oceans absorb isn’t constant. In the 1990s, ocean CO2 uptake dropped off, before increasing again in the 2000s. Recent research shows that the Southern Ocean was central to these changes.

The Southern Ocean is the most prolific of the oceans for carbon storage – accounting for approximately 40% of the global ocean CO2 uptake. In the 1990s, strengthening winds circulating around Antarctica affected ocean currents and brought carbon-rich water to the surface. This meant the ocean was less able to absorb CO2 from the atmosphere.

In the 2000s, the winds continued to strengthen, yet the CO2 uptake in the Southern Ocean rebounded. This, combined with increasing CO2 uptake in other oceans, suggested to scientists that there was, ultimately, another factor affecting the ocean carbon sink.

The new study says the reason lies in circulation patterns in the top 1,000m of the world’s oceans.

‘Missing piece of the puzzle’
The water in our oceans is constantly on the move. In the upper layers of the ocean there are several driving forces responsible, explains lead author Dr Tim DeVries, an assistant professor in oceanography at the University of California. He tells Carbon Brief:

“The [circulation patterns] are driven by winds and by ‘buoyancy forcing’ – which means changes in the density of surface waters due to changes in their temperature (heating/cooling) or salinity (adding/removing freshwater).”

Using observed data, the researchers built a computer model to simulate these circulation patterns in the upper ocean. They ran their model to analyse the exchange of CO2 between the ocean and atmosphere over recent decades.

They found that in the 1990s, the ocean circulation patterns were “more vigorous” and coincided with a big dip in CO2 uptake. From around 2000, the circulation patterns then weakened, bringing a rebound in CO2 uptake.

The simplified diagram below illustrates the effect these “overturning” circulation patterns have.

Stronger ocean overturning – as seen during the 1990s – brings more carbon-rich water up from the deeper ocean, the researchers say. When this water reaches the surface it releases CO2 into the atmosphere (see a). More vigorous overturning also means the ocean takes up more CO2 from the atmosphere (b), but not as much as the extra CO2 released.

As the bottom half of the diagram shows, weaker overturning in the 2000s reduces both the amount of CO2 released to the atmosphere (c), and what is absorbed again (d). Overall, this increases how much CO2 the ocean takes up.
Title: Re: Magnitude of future warming
Post by: Klondike Kat on September 24, 2019, 03:42:33 PM
Very nice gerontocrat.  The only constant in life is change - Heraclitus.

That said, we cannot predict what changes will occur.  In the absence of a known change, we assume a constant to minimize potential errors.
Title: Re: Magnitude of future warming
Post by: gerontocrat on September 24, 2019, 05:19:11 PM
So I took the data from NOAA & elsewhere from 1980 to 2018 on Global CO2 ppm & Emissions.

I converted CO2 ppm change to GT change, and from that got the GT sunk in GT & as % of emissions. I then made 10 year trailing averages as the yearly data is so spiky.

Hence the attached graph. The data shows a % and GT drop and then a rise sort of in line with what the science papers are saying about variations due to ocean circulation.

But the main conclusion remains the same, CO2 captured by the sinks increased as emissions increased.

So my question remains the same - will CO2 captured by the sinks decrease as emissions decrease? (or in another way- how sensitive is the chemical process that exchanges CO2 from air to ocean to small changes in CO2 ppm?)


https://link.springer.com/article/10.1007/s40641-018-0104-3
Quote
Models project that when net CO2 emissions are positive, but start to decline, the land and ocean carbon sinks will begin to weaken and take up less CO2 . Note that these responses may not be driven entirely by CO2 forcing as other factors such as a changing climate also affect the strength of these sinks. At some point, as net CO2 emissions decline, carbon sink uptake will exceed emissions input and the atmospheric CO2 concentration will begin to decline.

Title: Re: Magnitude of future warming
Post by: Klondike Kat on September 24, 2019, 05:55:28 PM

So my question remains the same - will CO2 captured by the sinks decrease as emissions decrease? (or in another way- how sensitive is the chemical process that exchanges CO2 from air to ocean to small changes in CO2 ppm?)


My answer is not directly.  I stand behind my claim that CO2 captured is a function of the concentration in the atmosphere, not the amount emitted.  When the captured amount exceeds the emitted amount, then the atmospheric concentration will decrease.  That will subsequently lead to decreased capture. 

Hence, it is indirectly related to emitted CO2, as decreasing emissions will eventually result in decreased atmospheric concentration, and consequently decreased capture.

Of course, this cannot be proven until emissions begin to decrease.
Title: Re: Magnitude of future warming
Post by: JMP on September 24, 2019, 09:44:56 PM
Hello all.  Love this thread.  It has been fascinating to follow.

So... I got to wondering and looked up some stuff.  My first question was about the finite-ness of the oceans and wondered if that might be a limiting factor. The information I found (as one might expect) says that this is a complex subject and still too little is known but, but, but....  :o   :o   :o 

Alarmingly also this:
Quote
As long as atmospheric CO2 concentrations continue to rise, the oceans will continue to take up CO2 .
However, this reaction is reversible. If atmospheric CO2 were to decrease in the future, the oceans will start releasing the accumulated anthropogenic CO2 back out into the atmosphere. [emphasis mine]

http://www.waterencyclopedia.com/Bi-Ca/Carbon-Dioxide-in-the-Ocean-and-Atmosphere.html#ixzz60TMnjmHg

Although, it does go on to say:
Quote
The ultimate storage place for anthropogenic CO2 must be reactions that bind the CO2 in a manner that is not easily reversed. Dissolution of calcium carbonate in the oceans, for example, is a long-term storage place for CO2 . As the oceans continue to take up anthropogenic CO2 , it will penetrate deeper into the water column, lowering the pH and making the waters more corrosive to calcium carbonate. The problem is that carbonate dissolution typically occurs in the deep ocean, well removed from the anthropogenic CO2 taken up in the surface waters. In portions of the North Atlantic and North Pacific Oceans, however, anthropogenic CO2 may have already penetrated deep enough to influence the dissolution of calcium carbonate in the water column.
Title: Re: Magnitude of future warming
Post by: oren on September 24, 2019, 11:10:55 PM
Quote
My answer is not directly.  I stand behind my claim that CO2 captured is a function of the concentration in the atmosphere, not the amount emitted.  When the captured amount exceeds the emitted amount, then the atmospheric concentration will decrease.  That will subsequently lead to decreased capture.  
KK you insist on ignoring the other factor, ocean surface concentration. The uptake of CO2 by the ocean in the near term is proportional to the atmospheric concentration less the ocean surface concentration (including the slower downward flux from the ocean surface to the deep ocean).  But the ocean surface concentration is a function of the past emitted CO2. Thus scrubbing of the CO2 from the atmosphere will be dependent on slower processes (assuming emissions stop at some point).
I expect that as a chemist this really should be crystal clear to you. The ocean surface equilibrates fast, and has already swallowed a lot of CO2, so further fast uptake is dependent on further increase in atmospheric partial pressure.
Title: Re: Magnitude of future warming
Post by: Klondike Kat on September 24, 2019, 11:53:56 PM
Quote
My answer is not directly.  I stand behind my claim that CO2 captured is a function of the concentration in the atmosphere, not the amount emitted.  When the captured amount exceeds the emitted amount, then the atmospheric concentration will decrease.  That will subsequently lead to decreased capture. 
KK you insist on ignoring the other factor, ocean surface concentration. The uptake of CO2 by the ocean in the near term is proportional to the atmospheric concentration less the ocean surface concentration (including the slower downward flux from the ocean surface to the deep ocean).  But the ocean surface concentration is a function of the past emitted CO2. Thus scrubbing of the CO2 from the atmosphere will be dependent on slower processes (assuming emissions stop at some point).
I expect that as a chemist this really should be crystal clear to you. The ocean surface equilibrates fast, and has already swallowed a lot of CO2, so further fast uptake is dependent on further increase in atmospheric partial pressure.

The gas exchange at the surface is but one aspect of the entire planetary sequestration process.  The mixing of the surface waters with the deep ocean takes much longer, as does calcification and other terrestrial sinks.  We have been operating under the assumption that planetary equilibrium is a slow process, and the atmospheric carbon dioxide lifetime is long.  Are you arguing for a fast equilibrium and short lifetime? 
Title: Re: Magnitude of future warming
Post by: Hefaistos on September 25, 2019, 07:45:04 AM
The gas exchange at the surface is but one aspect of the entire planetary sequestration process.  The mixing of the surface waters with the deep ocean takes much longer, as does calcification and other terrestrial sinks.  We have been operating under the assumption that planetary equilibrium is a slow process, and the atmospheric carbon dioxide lifetime is long.  Are you arguing for a fast equilibrium and short lifetime?

This topic is covered in AR5, WG1, chapter 9. Here is figure 9.26 on p. 793 showing the ocean part, the upper panel.
"With few exceptions, the CMIP5 ESMs also reproduce the large-scale pattern of ocean–atmosphere CO2 fluxes, with uptake in the Southern Ocean and northern
mid-latitudes, and outgassing in the tropics. However, the geographical
pattern of simulated land–atmosphere fluxes agrees much less well
with inversion estimates, which suggest a larger sink in the northern
mid-latitudes, and a net source rather than a sink in the tropics
." (p. 794)

In the figure we see another clear positive bias in how models estimate the atmosphere to ocean fluxfor such a long period as 1960-2005.

Figure byline to 9.26 Ensemble-mean global ocean carbon uptake (top) and global land carbon uptake (bottom) in the CMIP5 ESMs for the historical period 1900–2005. For comparison,
the observation-based estimates provided by the Global Carbon Project (Le Quere et al., 2009) are also shown (thick black line). The confidence limits on the ensemble mean are
derived by assuming that the CMIP5 models come from a t-distribution. The grey areas show the range of annual mean fluxes simulated across the model ensemble. This figure
includes results from all CMIP5 models that reported land CO2 fluxes, ocean CO2 fluxes, or both (Anav et al., 2013).
Title: Re: Magnitude of future warming
Post by: mdoliner on September 25, 2019, 08:02:11 PM
Does anybody know the math that connects an amount of warming to a level of greenhouse gases? Heat leaves the planet only through long wavelength radiation, and the amount of such radiation is a function of T4. Since ice melts using heat without raising temperature, the heat imbalance should last until the ice is gone. This is modified by the inefficiency of heat movement, but the ice will eventually melt, cooling the planet and reducing radiation, thus restoring the imbalance between energy in and energy out. It seems to me once this gets going it will continue until the ice is gone.

There is one posssible modification, albedo change. Open water has a lower albedo and so absorbs more radiation than ice. But open water also radiates more heat than ice. These two effects balance when the sun is roughly 13° or lower. Would the extra open water in the arctic be a negative or positive feedback?
Title: Re: Magnitude of future warming
Post by: nanning on September 25, 2019, 08:41:57 PM
I think that you'll find all the math in the models. There is not one single 'math' in this I think.

I would suggest studying Paleo climate data. That gives a good indication of the conditions in a balanced atmosphere. Right now of course, we don't have a balanced atmosphere. Our exceptionally large anthropogenically forced rate-of-change has no Paleo comparison.

Maybe you'll find this interesting:

On the causal structure between CO2 and global temperature
by Adolf Stips, Diego Macias, Clare Coughlan, Elisa Garcia-Gorriz & X. San Liang

https://www.nature.com/articles/srep21691
(whole article)
Title: Re: Magnitude of future warming
Post by: mdoliner on September 25, 2019, 09:52:32 PM
Thanks for the reply. I looked at that article. It is concerned with showing a correlation between warming and CO2, but my question is why would it stop at say, 1.5°, when there is still ice to keep the temperature down while more heat is absorbed.
Title: Re: Magnitude of future warming
Post by: sidd on September 25, 2019, 11:19:30 PM
For discussion on ice, albedo, radiative forcing, see Hansen's "Climate Change and Trace Gases".

https://pubs.giss.nasa.gov/abs/ha02210k.html

sidd
Title: Re: Magnitude of future warming
Post by: mdoliner on September 26, 2019, 08:26:41 PM
This too offers no justification for saying that the process will stop at, say 1.5 degrees. In the paleorecord warming reversed primarily because of rock weathering, which captured CO2. But that is a slow process (about a gigaton per year), not fast enough for the present situation. Again, since ice melts without raising temperature, and long wave radiation energy emission is a function of temperature, the imbalance should continue until the ice is gone or almost gone.
Title: Re: Magnitude of future warming
Post by: nanning on September 27, 2019, 04:19:44 AM
<snip>
the imbalance should continue until the ice is gone or almost gone.

If you mean the atmosphere with 'imbalance', then I agree. The oceans will keep warming up, driving ever more imbalance. The paleoclimate records show that CO2 and temperature are closely correlated in a balanced atmosphere. We may be undoing the late pliocene glaciation events if the current or higher CO2 level remains in the atmosphere for a long time. Ice as inertia is temporarily 'saving' us. Governing inertia and human behaviour inertia are 'dooming' us.
Title: Re: Magnitude of future warming
Post by: mdoliner on September 27, 2019, 04:35:20 AM
I mean by imbalance that there will be more heat coming into the earth via insolation than exits via high wavelength radiation.
Title: Re: Magnitude of future warming
Post by: Simon on September 27, 2019, 08:32:29 AM
Excellent work by Gerontocrat into carbon sinks. However, I am surprised to find the quantity in gigatonne of carbon sunk being on the same axis as percentage sunk given that total emissions are not constant.
Title: Re: Magnitude of future warming
Post by: Hefaistos on September 27, 2019, 09:15:33 AM


On the causal structure between CO2 and global temperature
by Adolf Stips, Diego Macias, Clare Coughlan, Elisa Garcia-Gorriz & X. San Liang

https://www.nature.com/articles/srep21691
(whole article)
'

Thanks Nanning, that is a cool paper!
Employing new methodology of information flow (IF) to test for causation. The issue is that the actual high correlation between rising CO2 levels and increasing surface temperatures alone is insufficient to prove that the increased radiative forcing resulting from the increasing GHG atmospheric concentrations is indeed causing the warming of the earth.
IPCC maintains that ‘detection’ and ‘attribution’ are still regarded as key priorities in climate change research. Correctly so, as GCM models are explicity built on the presumption of such causation, even though they lack fundamental theories and also data on essential things like e.g. water vapor, and aerosols.

Results are unambigious: GHG emissions not only correlate with global warming, they do indeed cause them.

Another very interesting aspect is the regional distribution of the amount of causation: "When analysing the IF from the global anthropogenic forcing to the GMTA (Fig. 3), in the Northern Hemisphere, we identified several regions of significant high causality. For example, IF takes largest values in Europe, North America, and China, densely populated and industrialized areas having shown strong recent warming2. On the other hand there are also regions with high causality like Siberia, the Sahel zone and Alaska that are not that much influenced by human activities. In the Southern Hemisphere, however, this IF distribution displays a most unexpected pattern, with high values in a large swath of the southern Atlantic, South Africa, parts of the Indian Ocean and Australia. This is true for both the total anthropogenic forcing (Fig. 3A) and the radiative forcing caused by CO2 alone (Fig. 3B). Therefore, despite CO2 being a globally well-mixed gas, the IF to surface temperature is regionally very different, showing sensitive areas."

Figure 3 byline: Shown is the spatial distribution of the information flow between the total anthropogenic forcing and the gridded global mean temperature anomalies (GMTA) (A) and the spatial distribution of the information flow between the radiative forcing caused by CO2 and the gridded global mean temperature anomalies (GMTA) (B).
Title: Re: Magnitude of future warming
Post by: gerontocrat on October 01, 2019, 08:18:55 PM
Excellent work by Gerontocrat into carbon sinks. However, I am surprised to find the quantity in gigatonne of carbon sunk being on the same axis as percentage sunk given that total emissions are not constant.
It isn't.

Percentages - refer to the right axis (green)
Amounts in GT - refer to the left axis (red).

Revised graph attached with amount left in atmosphere (in GT) added. (Also after rooting around online found a better figure to convert CO2 ppm to CO2 Gigatons - minor change).

Note that as regards percentages of CO2 sunk, the most often quoted figures are 30% Ocean, 26% Land, Total Percent of Emissions captured 56%.

The ten year average on 1980 to 2019 data is never higher than just over 52%.

If 2019 data ends up in line with current estimates, the percent of CO2 captured in 2019 will be only about 42%
Title: Re: Magnitude of future warming
Post by: blumenkraft on June 14, 2020, 05:33:15 PM
Climate worst-case scenarios may not go far enough, cloud data shows

Quote
Worst-case global heating scenarios may need to be revised upwards in light of a better understanding of the role of clouds, scientists have said.

...


“That is a very deep concern,” Johan Rockström, the director of the Potsdam Institute for Climate Impact Research, said. “Climate sensitivity is the holy grail of climate science. It is the prime indicator of climate risk. For 40 years, it has been around 3C. Now, we are suddenly starting to see big climate models on the best supercomputers showing things could be worse than we thought.”

He said climate sensitivity above 5C would reduce the scope for human action to reduce the worst impacts of global heating. “We would have no more space for a soft landing of 1.5C [above preindustrial levels]. The best we could aim for is 2C,” he said.

...

Timothy Palmer, a professor in climate physics at Oxford University and a member of the Met Office’s advisory board, said the high figure initially made scientists nervous. “It was way outside previous estimates. People asked whether there was a bug in the code,” he said. “But it boiled down to relatively small changes in the way clouds are represented in the models.”

The role of clouds is one of the most uncertain areas in climate science because they are hard to measure and, depending on altitude, droplet temperature and other factors, can play either a warming or a cooling role. For decades, this has been the focus of fierce academic disputes.

Previous IPCC reports tended to assume that clouds would have a neutral impact because the warming and cooling feedbacks would cancel each other out. But in the past year and a half, a body of evidence has been growing showing that the net effect will be warming. This is based on finer resolution computer models and advanced cloud microphysics.

...

The IPCC is expected to include the 5+C climate sensitivity figure in its next report on the range of possible outcomes. Scientists caution that this is a work in progress and that doubts remain because such a high figure does not fit with historical records.

...

Link >> https://www.theguardian.com/environment/2020/jun/13/climate-worst-case-scenarios-clouds-scientists-global-heating
Title: Re: Magnitude of future warming
Post by: The Walrus on June 14, 2020, 05:45:57 PM
One has to wonder it very small changes in the way clouds are considered makes such a huge difference in climate sensitivity, what would happen if those small changes were opposite in magnitude.
Title: Re: Magnitude of future warming
Post by: kassy on June 14, 2020, 06:28:41 PM
Previous IPCC reports tended to assume that clouds would have a neutral impact because the warming and cooling feedbacks would cancel each other out. But in the past year and a half, a body of evidence has been growing showing that the net effect will be warming. This is based on finer resolution computer models and advanced cloud microphysics.

So actually doing the maths on clouds shows they have a non neutral impact.

In a recent paper in the journal Nature, Palmer explains how the new Hadley Centre model that produced the 5+C figure on climate sensitivity was tested by assessing its accuracy in forecasting short-term weather.

This seems to be a good test:
https://www.nature.com/articles/d41586-020-01484-5

Pliocene weather is interesting for clouds too.

There is no opposite in magnitude because calculating less then not calculating is not really a magnitude.

Title: Re: Magnitude of future warming
Post by: The Walrus on June 15, 2020, 12:45:18 AM
Previous IPCC reports tended to assume that clouds would have a neutral impact because the warming and cooling feedbacks would cancel each other out. But in the past year and a half, a body of evidence has been growing showing that the net effect will be warming. This is based on finer resolution computer models and advanced cloud microphysics.

So actually doing the maths on clouds shows they have a non neutral impact.

In a recent paper in the journal Nature, Palmer explains how the new Hadley Centre model that produced the 5+C figure on climate sensitivity was tested by assessing its accuracy in forecasting short-term weather.

This seems to be a good test:
https://www.nature.com/articles/d41586-020-01484-5

Pliocene weather is interesting for clouds too.

There is no opposite in magnitude because calculating less then not calculating is not really a magnitude.

It is just a matter of semantics.  One could argue that less vs more is opposite in magnitude.  Regardless, they are claiming that the shortwave radiative effect (SCRE) will be less with future warming, although they state that the clouds will have a higher water content.  That seems opposite to established climate science, whereby increased water content leads to increased SCRE.
Title: Re: Magnitude of future warming
Post by: Hefaistos on June 15, 2020, 09:49:28 AM
This recent research finds a negative feedback for clouds in the ever important tropics.

The lightness of water vapor helps to stabilize tropical climate

Seth D. Seidel and Da Yang

Science Advances  06 May 2020:
Vol. 6, no. 19, eaba1951
DOI: 10.1126/sciadv.aba1951

Abstract
"Moist air is lighter than dry air at the same temperature, pressure, and volume because the molecular weight of water is less than that of dry air. We call this the vapor buoyancy effect. Although this effect is well documented, its impact on Earth’s climate has been overlooked. Here, we show that the lightness of water vapor helps to stabilize tropical climate by increasing the outgoing longwave radiation (OLR). In the tropical atmosphere, buoyancy is horizontally uniform. Then, the vapor buoyancy in the moist regions must be balanced by warmer temperatures in the dry regions of the tropical atmosphere. These higher temperatures increase tropical OLR. This radiative effect increases with warming, leading to a negative climate feedback. At a near present-day surface temperature, vapor buoyancy is responsible for a radiative effect of 1 W/m2 and a negative climate feedback of about 0.15 W/m2 per kelvin."

There is no settled science regarding the feedback of clouds and water vapor. In some situations/some places it's a negative feedback, in others it's a positive feedback.

GCM models are inherently unable to model convectice processes, as they operate on grid sizes that are about 1000 times bigger than the actual processes. Thus, the GCMs resort to parametrization of these processes. In other words, GIGO modelling.
Title: Re: Magnitude of future warming
Post by: The Walrus on June 15, 2020, 01:31:25 PM
Hefaistos,
I couldn't agree with you more. 
Title: Re: Magnitude of future warming
Post by: kassy on June 15, 2020, 02:49:49 PM
Quote
GCM models are inherently unable to model convectice processes, as they operate on grid sizes that are about 1000 times bigger than the actual processes. Thus, the GCMs resort to parametrization of these processes. In other words, GIGO modelling.

The Hadley validation test shows that if they use their cloud model parameter in short term weather forecasting it improves the forecasts so that is a hint that it actually works (similar to how they used the method to disprove another model challenge earlier).

And of course there are multiple levels on which we can take this.

 You are critical of the model. Fine. But...
Do you think the neutral assumption was more true then what we calculate? Or is it more a problem of magnitudes?
Is the GIGO postulation analysis driven or just because you don´t want it to be true?

I find GIGO kind of harsh. This is complicated stuff which needs tons of computing power.

Quote
Regardless, they are claiming that the shortwave radiative effect (SCRE) will be less with future warming, although they state that the clouds will have a higher water content.  That seems opposite to established climate science, whereby increased water content leads to increased SCRE.

Do you have a quote for that with a link to a paper?
Title: Re: Magnitude of future warming
Post by: The Walrus on June 15, 2020, 04:32:04 PM


Quote
Regardless, they are claiming that the shortwave radiative effect (SCRE) will be less with future warming, although they state that the clouds will have a higher water content.  That seems opposite to established climate science, whereby increased water content leads to increased SCRE.

Do you have a quote for that with a link to a paper?

I did not feel that I need a link to reference established science, but here goes:

https://earthobservatory.nasa.gov/features/Clouds
Title: Re: Magnitude of future warming
Post by: kassy on June 15, 2020, 10:04:26 PM
You need to link to where the people in the new research claim that: the shortwave radiative effect (SCRE) will be less with future warming, although they state that the clouds will have a higher water content.  That seems opposite to established climate science, whereby increased water content leads to increased SCRE.

Or where you think they do. Not some general background site with Alta Vista vibes.




Title: Re: Magnitude of future warming
Post by: jens on June 16, 2020, 02:24:04 AM
At least +4C, possibly up to +6C. Climate models are too imperfect to predict such things to great precision, especially on a timescale so far out. However, if events thus far have told us anything, climate models tend to underestimate the outcome due to lacking enough variables to make a proper projection. So I think I tend towards worse case scenarios.
Title: Re: Magnitude of future warming
Post by: The Walrus on June 16, 2020, 03:33:55 AM
You need to link to where the people in the new research claim that: the shortwave radiative effect (SCRE) will be less with future warming, although they state that the clouds will have a higher water content.  That seems opposite to established climate science, whereby increased water content leads to increased SCRE.

Or where you think they do. Not some general background site with Alta Vista vibes.

I am a tad confused with your post.  Why would I want to link to a claim that SCRE will be less with increased cloud cover, when it seems opposite to established science?
Title: Re: Magnitude of future warming
Post by: Hefaistos on June 16, 2020, 07:08:33 AM
Quote
GCM models are inherently unable to model convectice processes, as they operate on grid sizes that are about 1000 times bigger than the actual processes. Thus, the GCMs resort to parametrization of these processes. In other words, GIGO modelling.

The Hadley validation test shows that if they use their cloud model parameter in short term weather forecasting it improves the forecasts so that is a hint that it actually works (similar to how they used the method to disprove another model challenge earlier).

And of course there are multiple levels on which we can take this.

 You are critical of the model. Fine. But...
Do you think the neutral assumption was more true then what we calculate? Or is it more a problem of magnitudes?
Is the GIGO postulation analysis driven or just because you don´t want it to be true?

I find GIGO kind of harsh. This is complicated stuff which needs tons of computing power.

I have written at some length about this, and about the challenges facing the models before, in a number of posts. To sum up the arguments:

Model makers face 4 major challenges, as I see it:
1. GCM's lack a 'general theory' on water vapor on various latitudes and altitudes. Specifically, the tropics are challenging with the very powerful, energy intensive phase changes taking place (e.g. in the ubiquitos tropical thunderstorms).

2. There is a lack of understanding on the radiative forcing of clouds/water vapor. Is there a positive feedback, or a negative feedback between clouds and SST's? No-one knows. Recent research indicates that the feedback is negative in the tropics, but positive elsewhere. Specifically, IPCC doesn't know, and has previously just assumed that the feedback is zero. Yes, maybe better like that, than rely on GIGO models.

3. GCM's don't have the input data for the strongest GHG (water vapor/clouds) as they operate on MUCH larger grids than clouds, and the convective processes in clouds (currently a factor of more than 1000 between needed grid size, and feasible grid size). Thus, they have to rely on parameterizations for clouds and water vapor. That is a substandard practice, typical for GIGO models.

4. Computing capacity isn't big enough. Witness the GCM model E3SM, where they have severe restrictions on the length of runs they can make, and the number of runs they can afford, in terms of computing capacity and work time involved. GCMs typically use 100 km grid cells, whereas modelling of convective activity would require something like 0.1 km - 1 km cells. To reach this definition in a GCM would require in the order 10^10 times more powerful computers, as well as correspondig feed of input data. This won't happen in any foreseeable future.

All these challenges are clearly solvable, but I'd guess we need a couple of decades to get models that are more reliable as forecasting tools.

It's very disturbing that the enormous range of possible ECS's persists between these models. Currently, with AR5 and CMIP5, the range is from 1.5 - 4.5. And now we have the newer CMIP6 models, where maybe a fourth of them push for even higher ECS, up to 5.5 or so. But still, there are other CMIP6 models that maintain a ECS of 1.5 or so. Thus, the range seems to increase in the near future, in IPCC's AR6 Synthesis Report due in 2022. This is bizarre! How can we build a climate policy on such imprecise tools?!

As IPCC lacks tools for evaluating the quality and performance of models, and has decided to resort to give each model 'one vote', and together they form an ensemble of models. The hope is that the problems that different models have will be averaged out. This is a very crude approach. 

https://forum.arctic-sea-ice.net/index.php/topic,2205.msg234634.html#msg234634
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg231232.html#msg231232
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg232206.html#msg232206
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg243866.html#msg243866
https://forum.arctic-sea-ice.net/index.php/topic,2205.msg237028.html#msg237028
Title: Re: Magnitude of future warming
Post by: KiwiGriff on June 16, 2020, 09:58:40 AM
Quote
It's very disturbing that the enormous range of possible ECS's persists between these models. Currently, with AR5 and CMIP5, the range is from 1.5 - 4.5

CMIP5 models do not have a range encompassing 1.5C that lower bound is only derived from observational based modeling of ECS.
I doubt that a lower bound of 1.5C will hold into AR6 as much work has been published attempting to reconcile the low results of some observational based models with other methods.
https://www.carbonbrief.org/explainer-how-scientists-estimate-climate-sensitivity

(https://www.carbonbrief.org/wp-content/uploads/2019/03/Assessment-range-for-ECS-from-IPCC-AR5.jpg)
Title: Re: Magnitude of future warming
Post by: kassy on June 16, 2020, 02:45:09 PM
2. There is a lack of understanding on the radiative forcing of clouds/water vapor. Is there a positive feedback, or a negative feedback between clouds and SST's? No-one knows. Recent research indicates that the feedback is negative in the tropics, but positive elsewhere. Specifically, IPCC doesn't know, and has previously just assumed that the feedback is zero. Yes, maybe better like that, than rely on GIGO models.

We could sure do with more computing power. It´s not even that expensive.

I still disagree with the last part.

What they added is not perfect but it is not garbage either.

If you take your argument to the extreme that would mean you could never add new things to models and that is clearly wrong.
Title: Re: Magnitude of future warming
Post by: sidd on June 16, 2020, 09:22:27 PM
Re: models

This preprint is relevant:

https://arxiv.org/pdf/2005.11862.pdf

sidd
Title: Re: Magnitude of future warming
Post by: Ken Feldman on June 16, 2020, 11:44:45 PM
And Gavin Schmidt, a climate modeler, at Real Climate has provided an update as well:

http://www.realclimate.org/index.php/archives/2020/06/sensitive-but-unclassified-part-ii/ (http://www.realclimate.org/index.php/archives/2020/06/sensitive-but-unclassified-part-ii/)

Quote
Sensitive but unclassified: Part II
— gavin @ 13 June 2020

The discussion and analysis of the latest round of climate models continues – but not always sensibly.

Quote
Since then, more model results have been added to the archive, and thanks to Mark Zelinka, we can see some of the analysis as it updates in real time.

(https://forum.arctic-sea-ice.net/proxy.php?request=http%3A%2F%2Fwww.realclimate.org%2Fimages%2Fcmip6_ecs-2048x1493.png&hash=c5f64e3175444127834e7e5add2991b3)

Quote
By eye, it looks like there are two (or three) groups of models, one within the range of the assessed values (roughly 2 to 4.5ºC), one group with significantly higher values, and one institution/two models with a notably lower ECS. The question everyone has is whether this extended range is credible.

Quote
Since my first post, there have been a number of papers have looked at the skill of these models to see whether there are some key observational data that might help in constraining the sensitivity (and by extension, the projections into the future). One set of papers has focused on the global mean trends from 1990 or so onward which is a period of stable or declining aerosol trends and which might therefore be a closer test of the models’ transient sensitivity to CO2 than earlier periods. Notably Tokarska et al. (2020) and Njisse et al. (2020) suggest that many of the high ECS group warm substantially faster than observed over this period and therefore should be downweighted in the constrained projections of the future.

(https://pbs.twimg.com/media/ENmhkH7UEAEmvHs?format=jpg&name=900x900)

Quote
Recently however, writing in Guardian, Jonathan Watts uses results from the UK’s new model (Williams et al., 2020) and a commentary from Tim Palmer to argue that that we nonetheless need to take these high sensitivities more seriously, and indeed that they may indicate that the assessed ECS range has been underestimating potential changes in the future. This is however flawed.

The Williams et al paper demonstrates that updates to the HadGEM3‐GC3.1 model developed by the UK’s Hadley Centre that affect the clouds and aerosols, increase the skill of that model in short-term initialized weather forecasts. This is fine, and indeed, consistent with increases in skill in the newer models across the board when they are compared to a very broad range of observations.

But it is a logical leap to go from an observation of increased skill in one metric to assuming that therefore the overall ECS in this particular model is more likely. To demonstrate that, one would need to show that this particular measure of skill was specifically related to ECS which has not been done (a point Palmer acknowledges). To put in another way, it may be that all models that do well on this task have a range of ECS values, and that the coincidence of this one model doing well and having a high ECS, was just that, a coincidence.

The article goes into details about cloud water and the impact on sensitivity.  If you're interested, it's worth going over to the link to see why.

tl,dr:  The jury is still out on the high sensitivity models.
Title: Re: Magnitude of future warming
Post by: Hefaistos on June 17, 2020, 07:20:15 AM
Quote
It's very disturbing that the enormous range of possible ECS's persists between these models. Currently, with AR5 and CMIP5, the range is from 1.5 - 4.5

...
I doubt that a lower bound of 1.5C will hold into AR6 as much work has been published attempting to reconcile the low results of some observational based models with other methods.
https://www.carbonbrief.org/explainer-how-scientists-estimate-climate-sensitivity


You refer to an overview article in Carbonbrief. In that article they make a central claim regarding the most influential GHG, water vapour: "As the world warms, the amount of water vapour in the atmosphere is expected to increase and, therefore, so too will the greenhouse effect. Measurements from satellites confirm that water vapour concentrations have been increasing in step with temperatures in the atmosphere over the past few decades." , with a link to:
https://www.gfdl.noaa.gov/blog_held/48-increasing-vertically-integrated-water-vapor-over-the-oceans/
At the link, there is a chart that shows very slightly increasing water vapor over the oceans, but only in the tropics.
However, the data is not that straightforward, nor is it simple to interpret. At the NOAA Physical Sciences Laboratory (PSL) you can create charts of humidity. Relative atmospheric humidity (%) at three different altitudes in the lower part of the atmosphere (the Troposphere) is generally speaking going down.
Also specific atmospheric humidity (g/kg) is down on higher altitudes, and shows the stipulated uptrend only at surface level.
https://psl.noaa.gov/cgi-bin/data/timeseries/timeseries1.pl

Conflicting evidence regarding water vapour feedback!

We also have recent research showing that the cloud feedback in the tropics is negative. Already mentioned upthread, the paper by Seidel and Yang, in Science Advances  06 May 2020: DOI: 10.1126/sciadv.aba1951
https://forum.arctic-sea-ice.net/index.php/topic,2715.msg268667.html#msg268667

Conflicting evidence also regarding cloud feedback!

There are already several critical scientific evaluations of the CMIP6 models. Zelinka et al write:
"ECS is higher on average in CMIP6 due primarily to strengthened cloud feedbacks. Tropical low cloud feedbacks and global non‐low cloud feedbacks are positive in nearly every model."
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL085782

What if the CMIP models didn't get their physical processes right? What if the feedback in the most important sector, the tropics, is negative, as Seidel and Yang show?

Then it is the high ECS models that should be discarded, not the low ECS ones.
Title: Re: Magnitude of future warming
Post by: kassy on June 18, 2020, 01:41:00 AM
Nobody questions the first claim.

Quote
At the link, there is a chart that shows very slightly increasing water vapor over the oceans, but only in the tropics.
However, the data is not that straightforward, nor is it simple to interpret. At the NOAA Physical Sciences Laboratory (PSL) you can create charts of humidity.

Models very robustly maintain more or less constant relative humidity in these lower tropospheric layers over the oceans as they warm, basically due to the constraint imposed by  the energy balance of the troposphere on the strength of  the hydrological cycle, and the tight coupling between the latter and the low level relative humidity over the oceans.  Do we have observational evidence for this behavior?  The answer is a definitive yes, as indicated by the plot above of microwave measurements of total column water vapor compared to model simulations of the same quantity.

So the graphic is about 2 records agreeing.

It is also quite noisy but that fits with the water cycle.

I don´t think these graphics tell you much for two reasons.

1) For now this proces is stable but noisy as the graph shows. In the long term the signal will be modulated by CO2 piling up above the water vapor and methane changing to co2 + water high in the atmosphere.

2) The data set you get to play with goes from 1950 - 2020. Over that time frame the CO2 and CH4 effects are only present on the end of the range but not in a way they are detectable in your chosen metrics.
Title: Re: Magnitude of future warming
Post by: kassy on June 18, 2020, 02:47:09 AM
Something bug me about ECS

The equilibrium climate sensitivity (ECS) is the long-term temperature rise (equilibrium global mean near-surface air temperature) that is expected to result from a doubling of the atmospheric CO2 concentration (ΔT2×). It is a prediction of the new global mean near-surface air temperature once the CO2 concentration has stopped increasing and most of the feedbacks have had time to have their full effect. Reaching an equilibrium temperature can take centuries, or even millennia, after CO2 has doubled.

As we can see above clouds are a contentious issue but the actual land modelling isn´t that great either. Recent research has turned up a number of processes from permafrost that are not modelled (NO2 and carbon release via surface water).

We are awaking all kinds of earth processes we do not really understand and i think it is safe to say we constantly underestimate the consequences.

So we use ECS to see how bad it wil get. Theoretically ok but.

The real glaring problem is that in the whole IPCC proces they never set solid boundaries. What is acceptable damage?

Real sensible goals would be:
Prevent arctic ice from melting.
Prevent permafrost from becoming a source.
Prevent Antarctic glaciers becoming active.

We failed all those already at the current temperatures so technically we are in overshoot since CO2 hit 350 to 380 ppm. It´s rather hard to put a number on ECS if you have to account for all those things.

It is also redundant. It´s like standing in the garden and trying to run some numbers on the fire in the house.
Title: Re: Magnitude of future warming
Post by: Human Habitat Index on June 18, 2020, 03:24:56 AM
In my opinion based on following climate change since the 70s is that ECS, like the uncertainty of the preindustrial baseline, is a tool for obfuscation.

Why the doubling of co2, what is magical about that standard ?

After Copenhagen, I became a raging conspiracy theorist, leading me to discover many inconvenient truths in many areas besides CC.

But overall the momentum of industrial civilisation just overwhelms everything.

So I am a rational doomist because the situation is irreversible.
Title: Re: Magnitude of future warming
Post by: KiwiGriff on June 18, 2020, 04:01:06 AM
https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/ch3s3-4-2-2.html

In general, the radiosonde trends are highly suspect owing to the poor quality of, and changes over time in, the humidity sensors (e.g., Wang et al., 2002a). Comparisons of water vapour sensors during recent intensive field campaigns have produced a renewed appreciation of random and systematic errors in radiosonde measurements of upper-tropospheric water vapour and of the difficulty in developing accurate corrections for these measurements (Guichard et al., 2000; Revercombe et al., 2003; Turner et al., 2003; Wang et al., 2003; Miloshevich et al., 2004; Soden et al., 2004).

https://www.ipcc.ch/site/assets/uploads/2018/07/WGI_AR5.Chap_.2_SM-1.pdf
2.SM.6.2 Radiosonde Humidity Data
Since AR4 there have been three distinct efforts to homogenize the
tropospheric humidity records from operational radiosonde measurements (Durre et al., 2009; McCarthy et al., 2009; Dai et al., 2011) (Table
2.SM.9)


Abstract
[1] In an effort to update previous analyses of long‐term changes in column‐integrated water vapor, we have analyzed trends in surface‐to‐500‐hPa precipitable water (PW) calculated from radiosonde measurements of dew point depression, temperature, and pressure at approximately 300 stations in the Northern Hemisphere for the period 1973–2006. Inhomogeneities were addressed by applying a homogenization algorithm that adjusts for both documented and undocumented change points. The trends of the adjusted PW time series are predominantly upward, with a statistically significant trend of 0.45 mm decade−1 for the Northern Hemisphere land areas included in the analysis. Particularly significant increases are found in all seasons over the islands of the western tropical Pacific, and trends are also positive and statistically significant for the year as a whole and in at least one season in Japan and the United States. These results indicate that the widespread increases in tropospheric water vapor, which earlier studies had reported and shown to be physically consistent with concurrent increases in temperature and changes in moisture transport, have continued in recent years.
Radiosonde‐based trends in precipitable water over the Northern Hemisphere: An update
Imke Durre  Claude N. Williams Jr.  Xungang Yin  Russell S. Vose
First published:13 March 2009

Abstract
A new analysis of historical radiosonde humidity observations is described. An assessment of both known and unknown instrument and observing practice changes has been conducted to assess their impact on bias and uncertainty in long-term trends. The processing of the data includes interpolation of data to address known sampling bias from missing dry day and cold temperature events, a first-guess adjustment for known radiosonde model changes, and a more sophisticated ensemble of estimates based on 100 neighbor-based homogenizations. At each stage the impact and uncertainty of the process has been quantified. The adjustments remove an apparent drying over Europe and parts of Asia and introduce greater consistency between temperature and specific humidity trends from day and night observations. Interannual variability and trends at the surface are shown to be in good agreement with independent in situ datasets, although some steplike discrepancies are apparent between the time series of relative humidity at the surface. Adjusted trends, accounting for documented and undocumented break points and their uncertainty, across the extratropical Northern Hemisphere lower and midtroposphere show warming of 0.1-0.4 K decade(-1) and moistening on the order of 1%-5% decade (1)since 1970. There is little or no change in the observed relative humidity in the same period, consistent with climate model expectation of a positive water vapor feedback in the extratropics with near-constant relative humidity.

An Analysis of Tropospheric Humidity Trends from Radiosondes
Article (PDF Available) in Journal of Climate 22(22):5820-5838 · November 2009 with 76 Reads 
DOI: 10.1175/2009JCLI2879.1
Cite this publication
Mark P. McCarthy Et.al



One could look towards data we believe is reasonably accurate rather than relying on that we know is not.
Title: Re: Magnitude of future warming
Post by: Hefaistos on June 18, 2020, 11:50:06 AM
In my opinion based on following climate change since the 70s is that ECS, like the uncertainty of the preindustrial baseline, is a tool for obfuscation.

Why the doubling of co2, what is magical about that standard ?
...

Global annual mean CO2 concentration has increased by almost 50% since the start of the Industrial Revolution, from 280 ppm to 420 ppm now.
Doubling of CO2 means another 140 ppm to add. Currently we add maybe 2.2 ppm per year, and it has become a linear growth. So in 50 - 70 years with continued linear growth we will have doubled the CO2. Kind of graspable.

Testing with GCM models for the effects of a doubling of CO2 thus makes a lot of sense, per se.
Title: Re: Magnitude of future warming
Post by: KiwiGriff on June 18, 2020, 02:09:15 PM
Care to prove the keeling curve is now linear?
Or is that just your eyeballs?
https://scripps.ucsd.edu/programs/keelingcurve/2019/06/04/carbon-dioxide-levels-hit-record-peak-in-may/
Carbon Dioxide Levels Hit Record Peak in May
Quote
In Climate in the News, Keeling Curve History, Measurement Notes by Rob MonroeJune 4, 2019

Monthly average surpassed 414 parts per million at Mauna Loa Observatory

Atmospheric carbon dioxide continued its rapid rise in 2019, with the average for May peaking at 414.8 parts per million (ppm), according to instruments operated by Scripps Institution of Oceanography at the University of California San Diego at NOAA’s Mauna Loa Atmospheric Baseline Observatory, scientists from NOAA and Scripps announced today.

This is the highest seasonal peak recorded in 61 years of observations on top of Hawaii’s largest volcano, and the seventh consecutive year of steep global increases in concentrations of carbon dioxide, or CO2. The 2019 peak value was 3.5 parts per million higher than the 411.3 ppm peak reached in May 2018; it represents the second-highest annual jump on record.

Monthly CO2 values at Mauna Loa first breached the 400 ppm threshold in 2014.

May 2020:       417.07 ppm

https://scripps.ucsd.edu/programs/keelingcurve/
 
Title: Re: Magnitude of future warming
Post by: Tom_Mazanec on June 18, 2020, 03:49:37 PM
KiwiGriff:
If I read this right and my numbers are correct, CO2 went up 3.50 ppm May 2018 to May 2019, but only 2.27 ppm May 2019 to May 2020.
Could this reduction in increase (not a decrease) be a result of the shutdown?
Title: Re: Magnitude of future warming
Post by: dnem on June 18, 2020, 05:06:26 PM
I'm not sure if this is the most recent time Tamino has looked at it, but 2.5 years ago he concluded:

https://tamino.wordpress.com/2018/01/20/is-co2-still-accelerating/
Bottom line: CO2 is on the rise, the rise itself (velocity) has been getting faster (acceleration), and there’s no evidence at all that has changed recently.


I can't imagine there's enough data since then to definitively concluded that this has changed.
Title: Re: Magnitude of future warming
Post by: Hefaistos on June 19, 2020, 01:42:49 AM
Care to prove the keeling curve is now linear?
Or is that just your eyeballs?
...

I'm following Wolfpack's and Stephan's analyses of the CO2 at Mauna Loa, trying to detrend, and scrub the data from ENSO variability.

We clearly SEEM to have a slowdown in growth rate, and are almost on constant growth now.

https://forum.arctic-sea-ice.net/index.php/topic,2983.msg268712.html#msg268712

I have previously made a forecast somewhere on this forum that we will reach peak CO2 already by 2030. I still think it's possible due to the very strong growth of renewables. And certainly helped by corona lockdowns.
I expect to see a fall in the CO2 growth rate within a year.
Title: Re: Magnitude of future warming
Post by: Hefaistos on June 19, 2020, 08:20:25 AM
...

2) The data set you get to play with goes from 1950 - 2020. Over that time frame the CO2 and CH4 effects are only present on the end of the range but not in a way they are detectable in your chosen metrics.

You say that "the CO2 and CH4 effects are only present on the end of the range" /from 1950 - 2020/. You must be joking!
CO2 increases continously during this period of 70 years, and GMST have a strong positive trend, with some hiatuses. This should be reflected in the humidity levels, as the effect of increasing CO2 is supposed to go hand in hand with an increase in water vapour/humidity:

This is what they say at SkS:
"As water vapour is directly related to temperature, it's also a positive feedback - in fact, the largest positive feedback in the climate system (Soden 2005). As temperature rises, evaporation increases and more water vapour accumulates in the atmosphere. As a greenhouse gas, the water absorbs more heat, further warming the air and causing more evaporation. When CO2 is added to the atmosphere, as a greenhouse gas it has a warming effect. This causes more water to evaporate and warm the air to a higher, stabilized level. So the warming from CO2 has an amplified effect"
https://skepticalscience.com/water-vapor-greenhouse-gas-intermediate.htm

But the data shows no increase of water vapour, measured as specific humidity (or measured as relative humidity) in the LT. Only a small increase of specific humidity at the surface. (There is btw a bunch of interesting comments at SkS as well, e.g. #2 by someone called Victor.)

The research by Seidel and Yang that cloud feedback in the tropics is negative is also troubling, as clouds are the carriers of water vapour.
Title: Re: Magnitude of future warming
Post by: Hefaistos on June 19, 2020, 08:52:54 AM
...
One could look towards data we believe is reasonably accurate rather than relying on that we know is not.

Radiosonds have their problems, but since 1980 or so satellite data is presumably used.
We have the AQUA satellite with its Atmospheric Infrared Sounder (AIRS), and the Aura satellite, e.g.

According to NASA research, the satellite data shows less of an increase in humidity in the stratosphere, than models assume:
"Models that include water vapor feedback with constant relative humidity predict the Earth's surface will warm nearly twice as much over the next 100 years as models that contain no water vapor feedback.
Using the UARS /satellite/ data to actually quantify both specific humidity and relative humidity, the researchers found, while water vapor does increase with temperature in the upper troposphere, the feedback effect is not as strong as models have predicted. "The increases in water vapor with warmer temperatures are not large enough to maintain a constant relative humidity,""

This is what is shown in the charts in my post above.
https://forum.arctic-sea-ice.net/index.php/topic,2715.msg268929.html#msg268929
Relative humidity is consistently down on all altitudes measured.

https://www.nasa.gov/centers/goddard/news/topstory/2004/0315humidity.html