Magnitude of future warming

[ArcticMelt2]

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

"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/

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.

[ArcticMelt2]

There are estimates that the climate sensitivity may be 12 degrees.

[ArcticMelt2]

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).

[be cause]

Vote closes in 2099 ? b.c.

[b_lumenkraft]

Are you impatient or what? 

[pietkuip]

Centigrade or Fahrenheit? Please clarify the question.

[b_lumenkraft]

Why would anyone using Fahrenheit?? 

[Tom_Mazanec]

I assumed C, since this is on the World Wide Web and not the United States Wide Web.

[interstitial]

Why would anyone using Fahrenheit?? 

to confuse foreigners.

[Shared Humanity]

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.

[Tom_Mazanec]

I expect about 4 C. I voted 3-4, but could just as easily have voted for 4-5.

[KiwiGriff]

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.

[Sleepy]

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/

[ArcticMelt2]

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:



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.

[b_lumenkraft]

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?

[ArcticMelt2]

... 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.).

[b_lumenkraft]

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. 

[Wherestheice]

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

[Klondike Kat]

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.

[Archimid]

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.

[Shared Humanity]

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.

[Shared Humanity]

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?

[FrostKing70]

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.

[Klondike Kat]

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.

[Shared Humanity]

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.

[KiwiGriff]

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.

 

[Klondike Kat]

True on both points.  Projecting long term trends using short term data is a questionable practice.  Using an inappropriate dataset makes it worse.

[Shared Humanity]

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?

[gerontocrat]

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...

[crandles]

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.

[Klondike Kat]

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.

[Shared Humanity]

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.

[Klondike Kat]

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.

[oren]

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.

[Shared Humanity]

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.

[Klondike Kat]

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.

[SteveMDFP]

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.

[bbr2314]

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).

[SteveMDFP]

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.

[Archimid]

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.

[Tom_Mazanec]

Warming in 2050 1.4 K to 3 K:
https://www.nature.com/articles/ngeo1430

[vox_mundi]

'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, Nature (2019)

[wolfpack513]

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.

[KiwiGriff]

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 .

[Archimid]

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.

[Rod]

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.

[Juan C. García]

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.

[Juan C. García]

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! 

[El Cid]

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)

[wdmn]

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.