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How much warmer on Earth in 2100, compared to mid-19th century?

1-2 degrees
3 (3.3%)
2-3 degrees
11 (12.2%)
3-4 degrees
22 (24.4%)
4-5 degrees
26 (28.9%)
5-6 degrees
7 (7.8%)
6-10 degrees
15 (16.7%)
10-20 degrees
0 (0%)
20-50 degrees
0 (0%)
50-100 degrees
0 (0%)
Not enough information
6 (6.7%)

Total Members Voted: 89

Author Topic: Magnitude of future warming  (Read 7423 times)

Rich

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Re: Magnitude of future warming
« Reply #50 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.

Shared Humanity

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Re: Magnitude of future warming
« Reply #51 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.

johnm33

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Re: Magnitude of future warming
« Reply #52 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.

magnamentis

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Re: Magnitude of future warming
« Reply #53 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.

petm

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Re: Magnitude of future warming
« Reply #54 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.

wolfpack513

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Re: Magnitude of future warming
« Reply #55 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..

kassy

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Re: Magnitude of future warming
« Reply #56 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.
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b_lumenkraft

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Re: Magnitude of future warming
« Reply #57 on: July 05, 2019, 02:57:11 PM »
Another nail in the coffin of the 'carbon budget' myth.

ArcticMelt2

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Re: Magnitude of future warming
« Reply #58 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:



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.

magnamentis

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Re: Magnitude of future warming
« Reply #59 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.

ArcticMelt2

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Re: Magnitude of future warming
« Reply #60 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.


petm

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Re: Magnitude of future warming
« Reply #61 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.
« Last Edit: July 05, 2019, 07:16:56 PM by petm »

b_lumenkraft

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Re: Magnitude of future warming
« Reply #62 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

magnamentis

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Re: Magnitude of future warming
« Reply #63 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

magnamentis

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Re: Magnitude of future warming
« Reply #64 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.


petm

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Re: Magnitude of future warming
« Reply #65 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...

ArcticMelt2

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Re: Magnitude of future warming
« Reply #66 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



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.

kassy

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Re: Magnitude of future warming
« Reply #67 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.

Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

ArcticMelt2

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Re: Magnitude of future warming
« Reply #68 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



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.

ArcticMelt2

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Re: Magnitude of future warming
« Reply #69 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:





There is no limit for warming.

kassy

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Re: Magnitude of future warming
« Reply #70 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.

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wolfpack513

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Re: Magnitude of future warming
« Reply #71 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. 

Tom_Mazanec

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Re: Magnitude of future warming
« Reply #72 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.
SHARKS (CROSSED OUT) MONGEESE (SIC) WITH FRICKIN LASER BEAMS ATTACHED TO THEIR HEADS

vox_mundi

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Re: Magnitude of future warming
« Reply #73 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



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.
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vox_mundi

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Re: Magnitude of future warming
« Reply #74 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" Science Advances (2019).
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

Hefaistos

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Re: Magnitude of future warming
« Reply #75 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.
« Last Edit: September 19, 2019, 09:24:36 AM by Hefaistos »

KiwiGriff

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Re: Magnitude of future warming
« Reply #76 on: September 19, 2019, 12:00:09 PM »
CIMP3

CIMP5

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.

nanning

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Re: Magnitude of future warming
« Reply #77 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.
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Hefaistos

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Re: Magnitude of future warming
« Reply #78 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.

Hefaistos

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Re: Magnitude of future warming
« Reply #79 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.



Klondike Kat

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Re: Magnitude of future warming
« Reply #80 on: September 19, 2019, 02:53:40 PM »
CIMP3

CIMP5

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?

nanning

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Re: Magnitude of future warming
« Reply #81 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.
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wili

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Re: Magnitude of future warming
« Reply #82 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?
« Last Edit: September 19, 2019, 05:32:48 PM by wili »
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

El Cid

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Re: Magnitude of future warming
« Reply #83 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

wili

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Re: Magnitude of future warming
« Reply #84 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. 
"A force de chercher de bonnes raisons, on en trouve; on les dit; et après on y tient, non pas tant parce qu'elles sont bonnes que pour ne pas se démentir." Choderlos de Laclos "You struggle to come up with some valid reasons, then cling to them, not because they're good, but just to not back down."

KiwiGriff

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Re: Magnitude of future warming
« Reply #85 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.

Klondike Kat

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Re: Magnitude of future warming
« Reply #86 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.

sidd

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Re: Magnitude of future warming
« Reply #87 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

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Re: Magnitude of future warming
« Reply #88 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

sidd

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Re: Magnitude of future warming
« Reply #89 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

be cause

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Re: Magnitude of future warming
« Reply #90 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.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

nukefix

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Re: Magnitude of future warming
« Reply #91 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?

kassy

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Re: Magnitude of future warming
« Reply #92 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.
Þetta minnismerki er til vitnis um að við vitum hvað er að gerast og hvað þarf að gera. Aðeins þú veist hvort við gerðum eitthvað.

nanning

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Re: Magnitude of future warming
« Reply #93 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.
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vox_mundi

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Re: Magnitude of future warming
« Reply #94 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/
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

Klondike Kat

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Re: Magnitude of future warming
« Reply #95 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. 


mitch

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Re: Magnitude of future warming
« Reply #96 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.


vox_mundi

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“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― Leonardo da Vinci

Insensible before the wave so soon released by callous fate. Affected most, they understand the least, and understanding, when it comes, invariably arrives too late

oren

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Re: Magnitude of future warming
« Reply #98 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.

gerontocrat

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Re: Magnitude of future warming
« Reply #99 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.
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