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KiwiGriff

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AR6 physical science basis of climate change.
« on: August 02, 2021, 07:25:06 AM »
 The Intergovernmental Panel on Climate Change (IPCC) will release its next report, the Working Group I contribution to the Sixth Assessment Report (AR6), on 9 August 2021 .
A thread for comments and links
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kassy

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Re: AR6 physical science basis of climate change.
« Reply #1 on: August 07, 2021, 12:56:27 PM »
IPCC to Say Drastic Methane Cuts Necessary to Avert Climate Hell

Slashing carbon dioxide emissions will not be sufficient to avert climate disaster unless the international community also acts boldly to stop releasing methane, a powerful greenhouse gas that is playing an increasingly significant role in intensifying planetary heating and extreme weather.

The Intergovernmental Panel on Climate Change will issue that warning on Monday in the first of three reports that together will constitute the United Nations' sixth climate assessment since 1990, The Guardian reported Friday. According to the British newspaper, part one of the IPCC's forthcoming report, which covers physical science, "will show in detail how close the world is to irreversible change."

Although carbon dioxide remains in the atmosphere far longer, methane is up to 87 times more potent over a 20-year period, making it a key driver of global warming in the near term. Despite the pandemic-driven shutdowns in 2020, emissions of both heat-trapping gases reached record highs last year, the National Oceanic and Atmospheric Administration found.

Key sources of methane pollution include industrialized animal farming, landfills, and fossil fuel extraction and leaks. Research published last year showed that coal mining, oil drilling, and hydraulic fracturing for so-called "natural" gas may be emitting up to 40% more methane than previously thought. One climate scientist said that while the study was alarming, it "shows us where we can act on climate change" right away.

... continues:
https://www.commondreams.org/news/2021/08/06/ipcc-say-drastic-methane-cuts-necessary-avert-climate-hell

Two more days until the report comes out.
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Jim Hunt

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Re: AR6 physical science basis of climate change.
« Reply #2 on: August 07, 2021, 02:06:21 PM »
A "leak" of the AR6 WG1 SPM via Andrew Dessler:

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KiwiGriff

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Re: AR6 physical science basis of climate change.
« Reply #3 on: August 09, 2021, 10:34:12 AM »

Side-by-side comparison of the (left) original Mann et al (1999) “Hockey Stick” reconstruction as featured in the Summary for Policy Makers of the IPCC 3rd Assessment report (2001) and the (right) longer, sharper “Hockey Stick” as featured in the Summary for Policy Makers of the IPCC 6th Assessment report (2021).

Quote
A.2.2 Global surface temperature has increased faster since 1970 than in any other 50-year period over at least the last 2000 years (high confidence). Temperatures during the most recent decade (2011–2020) exceed those of the most recent multi-century warm period, around 6500 years ago13 [0.2°C to 1°C relative to 1850– 1900] (medium confidence). Prior to that, the next most recent warm period was about 125,000 years ago when the multi-century temperature [0.5°C to 1.5°C relative to 1850–1900] overlaps the observations of the most recent decade (medium confidence). {Cross-Chapter Box 2.1, 2.3, Cross-Section Box TS.1}

SPM AR6

Source a new post by Mike at Real Climate .
https://www.realclimate.org/index.php/archives/2021/08/a-tale-of-two-hockey-sticks/
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Jim Hunt

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Re: AR6 physical science basis of climate change.
« Reply #4 on: August 09, 2021, 11:03:06 AM »
The full version of the AR6 WG1 report seems to currently be unavailable, as is the Summary for Policymakers:

Quote
Disclaimer: The Summary for Policymakers (SPM) is the approved version from the 14th session of Working Group I and 54th Session of the Intergovernmental Panel on Climate Change and remains subject to final copy-editing and layout.

The Technical Summary (TS), the full Report Chapters, the Annexes and the Supplementary Materials are the Final Government Distribution versions, and remain subject to revisions following the SPM approval, corrigenda, copy-editing, and layout.

However an apparently not quite final version of chapter 9 can be downloaded. It states:

Quote
Accepted version subject to final editing

as well as:

Quote
Do Not Cite, Quote or Distribute

and:

Quote
The Arctic Ocean will likely become practically sea ice–free during the seasonal sea ice minimum for the first time before 2050 in all considered SSP scenarios. There is no tipping point for this loss of Arctic summer sea ice (high confidence). The practically ice-free state is projected to occur more often with higher greenhouse gas concentrations and will become the new normal for high-emission scenarios by the end of this century (high confidence). Based on observational evidence, Coupled Model Intercomparison Project Phase 6 (CMIP6) models and conceptual understanding, the substantial satellite-observed decrease of Arctic sea ice area over the period 1979–2019 is well described as a linear function of global mean surface temperature, and thus of cumulative anthropogenic CO2 emissions, with superimposed internal variability (high confidence). According to both process understanding and CMIP6 simulations, a practically sea ice–free state will likely be observed in some years before additional (post-2020) cumulative anthropogenic CO2 emissions reach 1000 GtCO2. {4.3.2, 9.3.1}
« Last Edit: August 09, 2021, 11:47:22 AM by Jim Hunt »
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kassy

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Re: AR6 physical science basis of climate change.
« Reply #5 on: August 09, 2021, 02:25:16 PM »
The link works now.
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Jim Hunt

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Re: AR6 physical science basis of climate change.
« Reply #6 on: August 09, 2021, 02:52:23 PM »
The link works now.

Yup. The TS & individual chapters are still the "beta" versions, but the full report and SPM now seem to be present and correct, albeit "subject to final copy-editing".

Quote
Figure SPM.8: Selected indicators of global climate change under the five illustrative scenarios used in this report.

The projections for each of the five scenarios are shown in colour. Shades represent uncertainty ranges – more detail is provided for each panel below. The black curves represent the historical simulations (panels a, b, c) or the observations (panel d). Historical values are included in all graphs to provide context for the projected future changes...

Panel b) September Arctic sea ice area in 10⁶ km² based on CMIP6 model simulations. Very likely ranges are shown for SSP1-2.6 and SSP3-7.0. The Arctic is projected to be practically ice-free near mid-century under mid and high GHG emissions scenarios.
« Last Edit: August 09, 2021, 03:53:04 PM by Jim Hunt »
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Richard Rathbone

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Re: AR6 physical science basis of climate change.
« Reply #7 on: August 09, 2021, 03:01:07 PM »

Source a new post by Mike at Real Climate .
https://www.realclimate.org/index.php/archives/2021/08/a-tale-of-two-hockey-sticks/

There's a whole suite of posts at Real Climate.

Overview of them all. https://www.realclimate.org/index.php/archives/2021/08/the-ipcc-sixth-assessment-report/

"AR6 of the Best. Half a dozen takeaways from the report from Gavin" is the one I recommend if you only read one of those posted so far.
https://www.realclimate.org/index.php/archives/2021/08/ar6-of-the-best/

The 6
Quote
Extreme events are increasingly connected to climate (duh!)
Sea level rise is a big deal
Use, abuse and misuse of the CMIP6 ensemble
The radiative forcing bar chart has gone full circle
Droughts and floods are complicated
Don’t mention the hiatus

gerontocrat

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Re: AR6 physical science basis of climate change.
« Reply #8 on: August 09, 2021, 03:50:06 PM »
https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf

I scanned the Summary for Policy Makers (& some of the technical report).

2050, 2100 is everywhere, but where is the here and now, like the need to cut CO2 emissions by 43% by 2030 to avoid +1.5 celsius.

Very much an invitation to politicians (like our Boris) to blah blah about net-zero by 2050.

There is a carbon budgets table (attached), but is from the beginning of 2020. So you can knock off 2020 emissions, and most certainly 2021 emissions, and probably 2022 emissions at or above 2019 levels from these budgets.

They report is sanguine (i.e. low likelihood) e,g.s about the likelihood of the whole Amazon becoming a CO2 emitter, and CO2 + CH4 emissions from permafrost increasing at a rapid rate.

EDIT:- The technical report does mention that the effect of AGW is masked quite a bit by aerosols.

Much of this is sulphur particles from coal burning. So if / when burning coal drops substantially (as is planned?) we are in for +1.5 & more anyway for some time? See the headline on Fox News - burn coal to keep us cool ?

The process of "consensus" as in "the Lowest Possible Denominator" has begun. It will continue up to and including the conference itself.

They say "Politics is the Art of the Possible". But what if the Possible falls far short of the Necessity?

click image for full size
« Last Edit: August 09, 2021, 04:56:34 PM by gerontocrat »
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gerontocrat

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Re: AR6 physical science basis of climate change.
« Reply #9 on: August 09, 2021, 04:59:03 PM »
https://www.theguardian.com/commentisfree/2021/aug/09/it-should-not-come-as-a-surprise-that-climate-change-is-worse-than-we-thought-and-also-getting-worser

Australia's First Dog on the Moon as usual has the defintive analysis from Brenda The Civil Disobedience Penguin.. click images to enlarge
"Para a Causa do Povo a Luta Continua!"
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kassy

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Re: AR6 physical science basis of climate change.
« Reply #10 on: August 09, 2021, 05:28:29 PM »
But what if the Possible falls far short of the Necessity?

Well then we don´t make it. They seem to assume Arctic ice holds out which i doubt and also they don´t have much to say about the Siberian fluxes because confidence is low. Last century it was something to preserve.

Also just plain crap formatting or can politicians parse this:

Quote
B.4.2 Based on model projections, under the intermediate scenario that stabilizes atmospheric CO2 concentrations this century (SSP2-4.5), the rates of CO2 taken up by the land and oceans are projected to decrease in the second half of the 21st century (high confidence). Under the very low and low GHG emissions scenarios (SSP1-1.9, SSP1-2.6), where CO2 concentrations peak and decline during the 21st century, land and oceans begin to take up less carbon in response to declining atmospheric CO2 concentrations (high confidence) and turn into a weak net source by 2100 under SSP1-1.9 (mediumconfidence). It is very unlikely that the combined global land and ocean sink will turn into a source by 2100
under scenarios without net negative emissions

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TeaPotty

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Re: AR6 physical science basis of climate change.
« Reply #11 on: August 09, 2021, 06:26:17 PM »
This politically filtered report is another bad joke on humanity.

Queue the optimists cheering on the next suicide-pact agreement with fantasy negative-emissions sci-fi tech. With the deniers on the other end defining the spectrum of debate in the media and politics, there is no room for honest discussion of the unfolding crisis that is our reality.

« Last Edit: August 09, 2021, 06:44:00 PM by TeaPotty »

KiwiGriff

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Re: AR6 physical science basis of climate change.
« Reply #12 on: August 10, 2021, 06:42:59 AM »
In-depth Q&A: The IPCC’s sixth assessment report on climate science.
carbon brief.
https://www.carbonbrief.org/in-depth-qa-the-ipccs-sixth-assessment-report-on-climate-science
Comprehensive and Well worth the time to read for a  over view of   AR6.

I found this interesting.
How have climate sensitivity estimates changed since AR5?
Quote
One of the most significant advances in the AR6 WG1 report is to narrow the range for “equilibrium climate sensitivity” (ECS), allowing for more confident projections of future warming.

The ECS is a key climate metric, first estimated by the scientist Svante Arrhenius in 1896, showing how much the world is expected to warm if CO2 levels double compared to pre-industrial levels.

(The concentration of CO2 in the atmosphere today is already around 50% higher than pre-industrial levels).

Despite decades of intensive research, ECS had remained stubbornly uncertain. Since AR5, however, there has been “substantial quantitative progress”, the AR6 report says, resulting in a central estimate of 3.0C, with a likely range of 2.5-4C and a very likely range of 2-5C.

This is much narrower than the AR5 likely range of 1.5-4.5C and very likely range of 1-6C.

Crucially, AR6’s WG1 says it is virtually certain that the ECS is larger than 1.5C and that “all lines of evidence help rule out” lower values.
Puts the Boot into the lukewarmers who insist its happening but not alarming by quoting the low end of AP5's estimates.
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sidd

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Re: AR6 physical science basis of climate change.
« Reply #13 on: August 10, 2021, 07:52:31 AM »
I skimmed chapter 9 and i am disturbed by the frequency of the term "deep uncertainty" with regard to Antarctica.

sidd

Jim Hunt

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Re: AR6 physical science basis of climate change.
« Reply #14 on: August 10, 2021, 10:40:02 AM »
How have climate sensitivity estimates changed since AR5?

See also another one of the "suite of posts at Real Climate":

https://www.realclimate.org/index.php/archives/2021/08/notallmodels/

Quote
For reference, out of 50 models, 40 are within the very likely AR6 range, and 23 within the likely range. Nonetheless of the 8 models with ECS > 5ºC, most are from very highly respected groups whose models do very well against comparisons of the climatology, including the Hadley Center (3 models), NCAR (2 models), DoE and the Canadian Climate Center (1 model each).


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kassy

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Re: AR6 physical science basis of climate change.
« Reply #15 on: August 10, 2021, 12:31:14 PM »
I skimmed chapter 9 and i am disturbed by the frequency of the term "deep uncertainty" with regard to Antarctica.

sidd

Well it only means ´we do not know enough´... what has been published on combined sea level rise already showed some uncomfortable truths for the Netherlands.

As soon as SLR hits 1-2 meters it will be really problematic. It means near coastal sand suppletion will not help. And as sea levels rise the salt will creep into the lands and it will push back river water.

All this is now projected for 2100 but it is still close enough to spook people and for experts to point out that we probably should not build houses in the lowest part of the river delta.

https://www.nu.nl/klimaat/6150389/zeespiegel-stijgt-bodem-zakt-moeten-we-nog-wel-bouwen-in-het-groene-hart.html

Of course the current projection is a rather safe bottom level with on top of that all that uncertainty. It will be interesting to see which Antarctic events of the many possible ones we will see first.

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Tor Bejnar

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Re: AR6 physical science basis of climate change.
« Reply #16 on: August 10, 2021, 04:00:57 PM »
Thanks for your posts, Jim an Kassy.  Why am I reminded of ASLR's repeated reminders that mainstream science (and government sponsored summaries of mainstream science) frequently avoids drama and frequently avoids discussing low-to-medium probability extreme futures?  ::) 

Property insurers mostly only look a year into the future.  Mortgage brokers used to guess 30 years into the future, but now they sell the mortgages to speculators (who ignore any warnings until almost or just too late - we have a term for it:  "bubbles").  So who is out there actually deciding what projects should and shouldn't be done?  Engineers who base projections on least-drama science?  Or more likely, last year's least-drama science.  :'(

Elon Musk, I understand, is preparing, in his hi-tech way, for the "pollute Earth now, pay later" bubble to burst.

So I ride my e-bike to work (and hope it doesn't rain on me too much on the way home - and it rains 'in the area' every day).
Arctic ice is healthy for children and other living things.

The Walrus

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Re: AR6 physical science basis of climate change.
« Reply #17 on: August 10, 2021, 06:24:39 PM »
I skimmed chapter 9 and i am disturbed by the frequency of the term "deep uncertainty" with regard to Antarctica.

sidd

There are reasons for the "deep uncertainty."  One is measurement uncertainty.  Another is forecasting uncertainty, particularly snow accumulation.  Recent research details some of this.

"We find that variations in snowfall are largest over longer periods (decades) and that traditional ways of estimating the natural variability underestimate the “noise” at these long periods, by a factor of up to about 10. As a result, it is harder to detect genuine changes in trends in Antarctic snowfall than previously thought—they will need to be larger or persist for longer to confidently detect them. It is clear, nonetheless, that Antarctica is losing overall mass due to increased discharge from key glaciers, and this is expected to dominate any changes to snowfall."

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL087493

AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #18 on: August 10, 2021, 07:51:40 PM »
I skimmed chapter 9 and i am disturbed by the frequency of the term "deep uncertainty" with regard to Antarctica.

sidd

There are reasons for the "deep uncertainty."  One is measurement uncertainty.  Another is forecasting uncertainty, particularly snow accumulation.  Recent research details some of this.

"We find that variations in snowfall are largest over longer periods (decades) and that traditional ways of estimating the natural variability underestimate the “noise” at these long periods, by a factor of up to about 10. As a result, it is harder to detect genuine changes in trends in Antarctic snowfall than previously thought—they will need to be larger or persist for longer to confidently detect them. It is clear, nonetheless, that Antarctica is losing overall mass due to increased discharge from key glaciers, and this is expected to dominate any changes to snowfall."

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL087493

I noted that:

a) If snowfall increases on key (those possibly subject to either MISI or MICI behavior) Antarctic marine glaciers, then this snowfall will increase the gravitational driving force that serve to potentially destabilize such marine glaciers in coming decades.
&
b) While a potential increase of snowfall on the Antarctic interior (and/or the Greenland interior) would serve to reduce future SLR, it would not reduce the freshwater flux from ice meltwater into the ocean and this flux serves to slow the MOC; which in-turn serves to accelerate climate change.
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A-Team

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Re: AR6 physical science basis of climate change.
« Reply #19 on: August 11, 2021, 12:54:52 AM »
I dunno how useful this 3,000 page report is (low confidence). The heavy focus on the far distant future 2050-2100 is a big mistake (high confidence). Providing 14,000 journal citations will not move the needle nor would 14,000,000 (very high confidence).

This report will end up serving those who want to kick the can down the road another 30 years before taking steps (very low confidence) that will be far more disruptive at this later time (high confidence). 

We could start tomorrow with a huge consumptive tax proportional to the emissions of production (eg beef) and useage (Ford F250) as citizen volunteerism is going nowhere at least in the US (extreme confidence).

Electric cars involve no societal adjustment whatsoever to the unworkable model of endless growth/consumerism (certainty). The change-over to wind and solar will not nearly enough (very high confidence) nor soon enough (extreme confidence).

We are already fed up here with the increasing extreme events of 2021 (very high confidence). The costs incurred this year alone in the US alone, trillions, could have paid a large installment towards a total makeover (high confidence).

To take these ever-increasing loses for another 30 years makes no economic or societal sense (very high confidence). This is a demographical and generational Ponzi scheme (certainty).

There’s no reason to think there will be the political will for de-growth even in mid-century (high confidence). The controlling wealthy have already lined up island bolt holes, don’t expect to experience personal difficulties, and fully intend to run the situation into the ground (very high confidence).
« Last Edit: August 11, 2021, 09:07:03 PM by A-Team »

I’M IN LOVE WITH A RAGER

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Re: AR6 physical science basis of climate change.
« Reply #20 on: August 11, 2021, 01:12:02 AM »
Despite the dead seriousness of the topic, that post made me laugh way harder than I expected, A-Team. I agree though, I think the framing of the information that was reported served to “keep a lid on things” while inching as close as possible to the dire warnings the data conveys. The bottom falls out one way or another, we just get to choose how rapid the process is, and the longer we delay, the harder reality is going to hit (as it already is, and we can look around us for proof)

KiwiGriff

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Re: AR6 physical science basis of climate change.
« Reply #21 on: August 11, 2021, 06:43:56 AM »
it is not us the aware that hold humanity back from taking the needed actions   
A few hundreds of thousands around the world are truly informed and conscious of the repercussions from our  little experiment in planetary atmospheric physics.
Its the other six billion who are oblivious to what is coming.
How do you make them accept what is needed in a democracy?
This is why politics is inseparable from the question and has a place on this blog.
One thing I take from AR6 is the possibility  of  severe consequence is no longer ignorable  without joining the equivalent of the flat earth society and denying well supported uncontroversial science.
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gerontocrat

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Re: AR6 physical science basis of climate change.
« Reply #22 on: August 11, 2021, 09:41:52 AM »
The "Summary for Policymakers" is in very dry technical language, which in itself disguises the true urgency of the situation. And can you see a politician like our blah-blah merchant Boris taking time to read it, study it, understand what needs to be done, and do it?

On the BBC's Radio4 one of the authors spoke in plain language and suddenly all was clear. What Policy Makers needed was a "Plain Language Summary", not a technical report where the authors showed off their technical expertise.

I agree with A-Team's post (high confidence), especially about the focus on 2050 and 2100.
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Richard Rathbone

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Re: AR6 physical science basis of climate change.
« Reply #23 on: August 11, 2021, 07:07:32 PM »
The "Summary for Policymakers" is in very dry technical language, which in itself disguises the true urgency of the situation. And can you see a politician like our blah-blah merchant Boris taking time to read it, study it, understand what needs to be done, and do it?

On the BBC's Radio4 one of the authors spoke in plain language and suddenly all was clear. What Policy Makers needed was a "Plain Language Summary", not a technical report where the authors showed off their technical expertise.


Imagine the SPM was written in Hungarian. Would Boris understand it better if it was written in plain Hungarian?

The SPM is an agreed international reference document. Its agreed by the policy makers and its written in the language the policy makers wanted and insisted on. Its not a piece of propaganda directed from English scientists to English people. Those with a technical education in a relevant discipline in an English speaking country will have fairly close to native understanding of it, but in general the SPM requires translation and its written in a style to support that.


vox_mundi

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Re: AR6 physical science basis of climate change.
« Reply #24 on: August 11, 2021, 08:45:48 PM »
Global Warming Begets More Warming, New Paleoclimate Study Finds
https://phys.org/news/2021-08-global-begets-paleoclimate.html

A new MIT study on extreme climate events in Earth's ancient history suggests that today's planet may become more volatile as it continues to warm.

The study, appearing today in Science Advances, examines the paleoclimate record of the last 66 million years, during the Cenozoic era, which began shortly after the extinction of the dinosaurs. The scientists found that during this period, fluctuations in the Earth's climate experienced a surprising "warming bias." In other words, there were far more warming events—periods of prolonged global warming, lasting thousands to tens of thousands of years—than cooling events. What's more, warming events tended to be more extreme, with greater shifts in temperature, than cooling events.

The researchers say a possible explanation for this warming bias may lie in a "multiplier effect," whereby a modest degree of warming—for instance from volcanoes releasing carbon dioxide into the atmosphere—naturally speeds up certain biological and chemical processes that enhance these fluctuations, leading, on average, to still more warming.

Interestingly, the team observed that this warming bias disappeared about 5 million years ago, around the time when ice sheets started forming in the Northern Hemisphere. It's unclear what effect the ice has had on the Earth's response to climate shifts. But as today's Arctic ice recedes, the new study suggests that a multiplier effect may kick back in, and the result may be a further amplification of human-induced global warming.

"When using these data to study extreme climate events, most studies have focused on individual large spikes in temperature, typically of a few degrees Celsius warming," Arnscheidt says. "Instead, we tried to look at the overall statistics and consider all the fluctuations involved, rather than picking out the big ones."

The team first carried out a statistical analysis of the data and observed that, over the last 66 million years, the distribution of global temperature fluctuations didn't resemble a standard bell curve, with symmetric tails representing an equal probability of extreme warm and extreme cool fluctuations. Instead, the curve was noticeably lopsided, skewed toward more warm than cool events. The curve also exhibited a noticeably longer tail, representing warm events that were more extreme, or of higher temperature, than the most extreme cold events.


... "This indicates there's some sort of amplification relative to what you would otherwise have expected," Arnscheidt says. "Everything's pointing to something fundamental that's causing this push, or bias toward warming events."

"It's fair to say that the Earth system becomes more volatile, in a warming sense," Rothman adds.


Climate–carbon cycle disruptions in the early Eocene, as recorded in benthic foraminiferal δ18O and δ13C data (13).
A 1-Ma running mean has been subtracted to isolate the sub-million-year fluctuations. (A and B) Time series and (C and D) histograms of the data points. The largest hyperthermals manifest as extreme events in an empirical probability distribution with an asymmetric non-Gaussian tail [near the asterisks in (C) and (D)]. This asymmetry quantifies an apparent bias toward extreme events involving global warming and oxidation of organic carbon. Note that the vertical axes decrease upward. 


Asymmetry of extreme Cenozoic climate-carbon cycle events, Science Advances (2021)
https://advances.sciencemag.org/content/7/33/eabg6864.full
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gerontocrat

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Re: AR6 physical science basis of climate change.
« Reply #25 on: August 11, 2021, 11:22:21 PM »
The WG1 report does identify CH4 reduction's importance.

https://www.bbc.co.uk/news/science-environment-58174111
Climate change: Curbing methane emissions will 'buy us time'

Quote
An aggressive campaign to cut methane emissions can buy the world extra time to tackle climate change, experts say.

One of the key findings in the newly released IPCC report is that emissions of methane have made a huge contribution to current warming. The study suggested that 30-50% of the current rise in temperatures is down to this powerful, but short-lived gas.

Here is an abstract from a paper written in 2003 that states that in the short run reducing CH4 emissions is the most cost-effective way of mitigating global heating. Nearly 20 years opportunity thrown down the drain.
https://link.springer.com/article/10.1023/A:1022196517982
Methane Emission Reduction: An Application of FUND

Quote
Abstract
Methane is, after carbon dioxide, the most important anthropogenic greenhouse gas. Governments plan to abate methane emissions. A crude set of estimates of reduction costs is included in FUND, an integrated assessment model of climate change. In a cost-benefit analysis, methane emission reduction is found to be instrumental in controlling the optimal rate of climate change. In a cost-effectiveness analysis, methane emission reduction largely replaces carbon dioxide emission reduction. Methane emission reduction reinforces the case for international cooperation in climate policy, but complicates the efficient allocation of emission reduction efforts. Methane emission reduction at the short run does not help to achieve the ultimate objective of the Framework Convention on Climate Change.
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aslan

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Re: AR6 physical science basis of climate change.
« Reply #26 on: August 12, 2021, 02:40:03 PM »
The link works now.

Yup. The TS & individual chapters are still the "beta" versions, but the full report and SPM now seem to be present and correct, albeit "subject to final copy-editing".

Quote
Figure SPM.8: Selected indicators of global climate change under the five illustrative scenarios used in this report.

The projections for each of the five scenarios are shown in colour. Shades represent uncertainty ranges – more detail is provided for each panel below. The black curves represent the historical simulations (panels a, b, c) or the observations (panel d). Historical values are included in all graphs to provide context for the projected future changes...

Panel b) September Arctic sea ice area in 10⁶ km² based on CMIP6 model simulations. Very likely ranges are shown for SSP1-2.6 and SSP3-7.0. The Arctic is projected to be practically ice-free near mid-century under mid and high GHG emissions scenarios.

One thing that is not explicitly state in the summary, and we need to dig deep in the report to find it, is that models are still underestimating the trend. Models of the CIMP6 are better aligned with observations, but still struggle to follow the trend. Observations are within the enveloppe, but most models with low sea ice also have low trends...

P.S. : A complementary quote, which have its importance :

Quote
Examining the sea-ice loss per degree of global warming, we find that only 11 out of 40 CMIP6 models are within the plausible range of 4.01 ± 1.28 × 106m2
of sea-ice loss per degree of warming (Figure 1d and Table S3). This is comparable to CMIP5, where 9 out of 40 models were within this plausible range (Figure 1d and Table S2). In CMIP3, not a single model provided a plausible sensitivity (Figure 1d). Also, the CMIP6 multimodel ensemble mean of Arctic sea-ice loss for a given amount of global warming is closer to (but still
outside) the plausible range than the multimodel ensemble mean of both CMIP5 and CMIP3. This might indicate an improvement of CMIP6 models over previous CMIP phases on a process level, given that the main physical link of sea-ice loss to any change in external forcing is given by a change in temperature.
However, as before, this might also be a reflection of a more realistic historical forcing of CMIP6 compared to CMIP5 and CMIP3.
While the more realistic simulation of these two sensitivities might indicate progress in CMIP6 models' capability to simulate the ongoing loss of Arctic sea ice, as in CMIP5 (Rosenblum & Eisenman, 2017) few CMIP6 models are able to simulate a plausible amount of sea-ice loss and simultaneously a plausible change in global mean temperature over time (or cumulative anthropogenic CO2 emissions). Of the CMIP6 models
analyzed here, these are ACCESS-CM2, BCC-CSM2-MR, CNRM-CM6-1-HR, FGOALS-f3-L, FIO-ESM-2-0,
GFDL-ESM4, GISS-E2-1-G, GISS-E2-1-G-CC, MPI-ESM-1-2-HAM, MPI-ESM1-2-HR, MPI-ESM1-2-LR,
MRI-ESM2-0, and NorESM2-MM. For the other CMIP6 models, those models that have a reasonable sea-ice loss tend to have too much global warming, while those models that simulate reasonable global warming simulate too little sea-ice loss (Figure 1g and Table S3). In particular, the models with a high sensitivity of Arctic sea-ice area to anthropogenic CO2 emissions also display a high sensitivity of global mean temperature to CO2 emissions. Hence, understanding this high climate sensitivity is most likely key to understanding why some CMIP6 models display such rapid loss of Arctic sea ice. A recent study suggested this high sensitivity to be caused by stronger cloud feedbacks (Zelinka et al., 2020).
If we plot the two sensitivity metrics against each other, it is generally impossible to distinguish a given CMIP6 model from the cloud given by CMIP5 models, with the exception of the highly sensitive CMIP6 simulations that clearly fall outside the cloud of previous CMIP phases (Figure 1g). The lack of both such high-sensitive simulations and of very low-sensitive simulations in CMIP5 might be one reason that the correlation between the two metrics is lower for CMIP5 than for CMIP3 and CMIP6.
In summary, we find that over the period 1979–2014, CMIP6 models on average simulate a sensitivity of Arctic sea ice that is closer to the observed value than CMIP5 and CMIP3 models, both relative to a given CO2 emission (as a proxy for time) and to a given warming. However, only few models are able to simulate a plausible sea-ice loss sensitivity to cumulative CO2 emissions and simultaneously a plausible rise in GMST.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2019GL086749

Not good...
« Last Edit: August 12, 2021, 02:48:09 PM by aslan »

TeaPotty

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Re: AR6 physical science basis of climate change.
« Reply #27 on: August 12, 2021, 06:50:53 PM »
The WG1 report does identify CH4 reduction's importance.

Any optimist care to apologize for years of downplaying CH4 and dismissing those looking at the evidence? This forum is full of it, but you never see remorse from these people.

Of course, a real scientist enjoys learning new evidence that shows where he could be wrong, what he's missing, and don't hang on to their pride.

kassy

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Re: AR6 physical science basis of climate change.
« Reply #28 on: August 12, 2021, 07:02:35 PM »
The "Summary for Policymakers" is in very dry technical language, which in itself disguises the true urgency of the situation. And can you see a politician like our blah-blah merchant Boris taking time to read it, study it, understand what needs to be done, and do it?

On the BBC's Radio4 one of the authors spoke in plain language and suddenly all was clear. What Policy Makers needed was a "Plain Language Summary", not a technical report where the authors showed off their technical expertise.


Imagine the SPM was written in Hungarian. Would Boris understand it better if it was written in plain Hungarian?

Rasmus on RealClimate also has some criticism on length and format of the SPM, see link which also includes A shorter summary for policy-makers in layman terms:

https://www.realclimate.org/index.php/archives/2021/08/deciphering-the-spm-ar6-wg1-code/

The SPM is not an easy read.

The more fatal flaw is that somehow everyone is looking at the long term. Yes it is nice to know what the end result of our labors will be but somehow we are ignoring things that already happened.

We lost the Siberian permafrost as a sink, we lost the northern forests as a sink and we lost the Amazon as a sink. 

The ASI is next in the firing line but they assume it to be safe but see aslans post about the models above. A lot of what we really know comes from ice age freezing and thawing. We know much less about the change away from that. We know even less about that happening with the current background rates because they are unprecedented.

Working out the ice loss on a global modal is not going to tell you what you need to do to safe the Arctic Ice which is rather critical.
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DanLittle

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Re: AR6 physical science basis of climate change.
« Reply #29 on: August 12, 2021, 08:35:05 PM »
Seems like some scientists got tired of governments watering down the reports and leaked a draft version of the part due in March. I tried following the link in the guardian article for the full text but couldn't habla the Espanola from the Spanish publication that initially leaked it. The IPCC says the internal draft of the summary for policy makers has already shifted from the version they sent out for review.

https://www.theguardian.com/environment/2021/aug/12/greenhouse-gas-emissions-must-peak-within-4-years-says-leaked-un-report

Sciguy

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Re: AR6 physical science basis of climate change.
« Reply #30 on: August 12, 2021, 10:16:31 PM »
The WG1 report does identify CH4 reduction's importance.

Any optimist care to apologize for years of downplaying CH4 and dismissing those looking at the evidence? This forum is full of it, but you never see remorse from these people.

Of course, a real scientist enjoys learning new evidence that shows where he could be wrong, what he's missing, and don't hang on to their pride.

Optimists on this site have been talking about methane reductions for years.  It’s one of the key strategies for mitigating future temperature rise.  Here’s a recent post as an example:

Methane is a short lived greenhouse gas with an average residence time in the atmosphere of 11 to 12 years.  From the late 1990s until 2007, concentrations of methane in the atmosphere were nearly stable.  Recently, it's been determined that fugitive emissions from coal mines and oil and gas drilling and pipelines are responsible for the increases in methane concentrations since 2007.  A large portion of the methane emissions from fossil fuels are leaks that occur from the active infrastructure while the fuels are produced and transported. 

Abandoned fossil fuel infrastructure also contributes to the methane emissions.  Methane emissions from abandoned coal mines and oil and gas infrastructure can be ended quickly by flooding the coal mines and plugging leaks in the oil and gas infrastructure.  Once that happens, methane concentrations will begin to decrease.

Here is a paper on what will happen when methane concentrations start to decrease.

https://link.springer.com/article/10.1007/s10584-020-02794-3

Quote
Smith, S.J., Chateau, J., Dorheim, K. et al. Impact of methane and black carbon mitigation on forcing and temperature: a multi-model scenario analysis. Climatic Change 163, 1427–1442 (2020). https://doi.org/10.1007/s10584-020-02794-3

Abstract

The relatively short atmospheric lifetimes of methane (CH4) and black carbon (BC) have focused attention on the potential for reducing anthropogenic climate change by reducing Short-Lived Climate Forcer (SLCF) emissions. This paper examines radiative forcing and global mean temperature results from the Energy Modeling Forum (EMF)-30 multi-model suite of scenarios addressing CH4 and BC mitigation, the two major short-lived climate forcers. Central estimates of temperature reductions in 2040 from an idealized scenario focused on reductions in methane and black carbon emissions ranged from 0.18–0.26 °C across the nine participating models. Reductions in methane emissions drive 60% or more of these temperature reductions by 2040, although the methane impact also depends on auxiliary reductions that depend on the economic structure of the model. Climate model parameter uncertainty has a large impact on results, with SLCF reductions resulting in as much as 0.3–0.7 °C by 2040. We find that the substantial overlap between a SLCF-focused policy and a stringent and comprehensive climate policy that reduces greenhouse gas emissions means that additional SLCF emission reductions result in, at most, a small additional benefit of ~ 0.1 °C in the 2030–2040 time frame.

Quote
A second set of auxiliary reduction mechanisms are physical effects related to changing methane concentrations. Decreasing methane emissions decreases temperatures, the oxidation of CH4 to CO2, the production of tropospheric ozone, and the production of stratospheric water vapor (all included in MAGICC). All of these forcing mechanisms contribute to the auxiliary forcing reductions and their magnitude is quantified in the lower set of model auxiliary results noted above (e.g., ~ 0.03 W/m2 in 2050). The largest contributor to the CO2 decrease is smaller carbon-cycle feedbacks due to decreased global temperatures. Note that there is additional forcing uncertainty for some of these mechanisms as compared with methane forcing itself. We also note that in the configuration used here, all anthropogenic methane is assumed to be oxidized to CO2, where in reality only fossil CH4 emissions should be considered to add to atmospheric CO2 concentration (Boucher et al. 2009), which will lead to an overestimate of the effect of CH4 oxidation.

There are many posts in the Policies and Solutions section of this forum that illustrate how to reduce methane emissions.  The solutions include stopping coal mining (which releases a lot of methane into the atmosphere), stopping oil and gas drilling, plugging abandoned oil and gas wells, improving cattle feed, and using agricultural waste methane as industrial feedstocks (for things like fertilizers) instead of fossil gas.

TeaPotty

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Re: AR6 physical science basis of climate change.
« Reply #31 on: August 13, 2021, 05:37:49 AM »
Your quote is from 2021. Look back 10 years, and you see the optimists on the wrong side, as usual. Many would even ask "why are we even talking about CH4?"

The pattern is always the same. Optimists deny the evidence bc it interferes with their subjective bubbles, call others alarmists, and gradually concede while shifting goalposts and claiming the "science has evolved".

Same pattern with Covid. Optimists arguing against and gradually conceding:
declaring the pandemic, the need for masks, recognizing airborne transmission, LongCovid, admitting child infections are not rare or benign, admitting Covid is evolving quickly and with worse variants, admitting vaccines don't stop transmission, and now breakthrough infections.

Many people who took optimists' advice died, especially on not needing masks.
Unfounded optimism is dangerous to society.

A-Team

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Re: AR6 physical science basis of climate change.
« Reply #32 on: August 13, 2021, 04:29:56 PM »
Quote
scientific opinion leaders are on the wrong side of methane
So true. They have been bashing methane for decades. Every aspect of it from change in hydroxyl radical to melting permafrost to ESS emissions to imaginary seaweed additives for range cows.

The giveaway is picking a 100 year time frame for methane rather than a 20 year or its half-life or instantaneous. Literally thousands of articles have taken the 100 year path.

The preferred narrative has always been carbon dioxide alone and the inane quest to refine S Arrhenius' estimate of the effect of its doubling (ignoring the intermediate decades with too-hard-to model effects, immense costs of extreme events and model-wrecking tipping points). 

Do nothing until the 2050-2100 time frame (except renew our goofy grants). Controversy avoidance, plain and simple -- go along to get along with the beef and oil/gas industries and growth of GDP consumerism. Documented thousands of times in the 19,512 posts by AbruptSLR.

Organized too, just like bashing the Wuhan lab leak for the last 18 months until too many emails from FOIA and cloud searches emerged, making this impossible. Sickening compliance from 'respected' journals whose holding companies do big business with China.

https://twitter.com/TheSeeker268

Look at the last twenty years of climate change coverage in Science magazine, eg some methane bubbles off Svalbard dissolved on the way up. Not to worry. Some futuristic carbon capture technology will surely come along, full steam ahead.

This also happened with the human genome project. The leading poobahs fought it bitterly saying boutique labs one gene at a time hypothesis driven research only, with this only collapsing as C Ventor went ahead with sequencing and privatization. Then the poobahs fought whole genome annotation, not model-system organisms etc etc.

Finally they flipped, pretending they supported it all along (even crediting themselves with proposing it!). Just like lab leak pandemics and methane/NOx/SF6, leading from behind.

How many well methane leaks in the San Juan Basin are addressed in the last massive infrastructure bill (aka let's emit more)? They've been going on since the 1920's. California feedlots where the methane emissions can be seen from space -- what's new there?

Instead we get 2,000 new oil/gas leases on public land since January and greenlighting of the tar sands Line 3 pipeline. New gas taxes to discourage consumption when top Biden advisors are ranting about  $3.19/gal? Europe has not collapsed with 2x those costs. Remember when Obama killed solar with panel protectionism tariffs -- were those lifted on day one?

Absolutely nothing has been accomplished until the gas curves bend down. Right now, they're bending up worse than ever, no sign of flattening even.

Fake futuristic optimism is not fixing anything.
« Last Edit: August 14, 2021, 12:00:07 AM by A-Team »

kassy

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Re: AR6 physical science basis of climate change.
« Reply #33 on: August 13, 2021, 04:54:00 PM »
The only thing that matters is our actions.

The solutions include stopping coal mining (which releases a lot of methane into the atmosphere), stopping oil and gas drilling, plugging abandoned oil and gas wells, improving cattle feed, and using agricultural waste methane as industrial feedstocks (for things like fertilizers) instead of fossil gas.

If we do those first two things we address both issues.
However all these things will take time.
Being optimistic is nice but can you stay optimistic if we take the actual political response into account? Pledges and champagne in Paris but not that much action.

The Earth system only sees real inputs and reacts to them. What we pledge but not deliver does nothing, any technology we dream of but don´t have does nothing. We can plant a billion trees but how much will burn?

The failing sinks listed above are not a problem?

It still feels weird to me how people brush of such tremendous switches.. Back in the nineties preserving permafrost was one of the goals but that chance has gone. It will grow as a source just like the Amazon.

The ASI will not be there forever.

The only real thing that helps is actual reductions in fossil fuel use and until we see that agreed to and done optimism does not mean anything.
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vox_mundi

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Re: AR6 physical science basis of climate change.
« Reply #34 on: August 14, 2021, 01:01:33 AM »
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― anonymous

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

AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #35 on: August 15, 2021, 06:27:15 PM »
...
The preferred narrative has always been carbon dioxide alone and the inane quest to refine S Arrhenius' estimate of the effect of its doubling (ignoring the intermediate decades with too-hard-to model effects, immense costs of extreme events and model-wrecking tipping points). 

Do nothing until the 2050-2100 time frame (except renew our goofy grants). Controversy avoidance, plain and simple -- go along to get along with the beef and oil/gas industries and growth of GDP consumerism. Documented thousands of times in the 19,512 posts by AbruptSLR.

...

In the linked 2021 article (see extracts below), Hansen makes it clear that consensus climate science model projections (e.g.: CMIP) significantly overestimate the current mixing of the ocean (i.e.: they assume fast mixing) that result in relatively slow increases in GMSTA, while Hansen's (& his associate's) model projections were tuned to match the observed slower ocean mixing (resulting in a more stratified ocean with a stronger 'pattern effect' that consensus climate scientists do not consider in calculating ECS, but which the MCDS-BN considers when estimating ECSeff) as illustrated by the first image.

In this article Hansen (whom I agree with, and whose work I based my Maximum Credible Domino Scenario-Bayesian Network, MCDS-BN, projections) expresses his concern that the Southern Ocean Meridional Overturning Circulation (SMOC, that is close related to Antarctic Bottom Water, AABW, formation) will temporarily shutdown circa 2050 (see the second image), which his (& his associate's) 2014 model projections (released in 2015 and published in 2016) would correspond to a marked slowdown of the AMOC circa 2100 (see the third image); due to the bipolar seesaw system (& subsystems) illustrated in the fourth image.

Thus, I concur with Hansen that consensus climate science projection severely underestimate the climate risks of the deep uncertainties associated with the credible interactions between the MOC (including both the AMOC and the SMOC) and possible freshwater fluxes (particularly from ice melting) into the ocean in coming decades.

Title: "Foreword: Uncensored Science Is Crucial for Global Conservation" by James Hansen 2021

www.columbia.edu/~jeh1/mailings/2021/20210614_ForewordHansen.pdf

Extract: "In October 2006 we – Reto Ruedy, Makiko Sato and I – made a model run with meltwater injection from Antarctica and Greenland. The initial ice melt rate was from observations; it then increased with a 10-year doubling time up to a sea level rise of 5 meters. Most of that water could be provided by West Antarctic ice, which rests on bedrock below sea level (Foreword Figure 2). Deep valley outlets on East Antarctica (Greenbaum et al., 2015) and Greenland (Catania et al., 2020) expose additional ice to contact with ocean water.

Within several decades the North Atlantic and Southern Ocean Overturning Circulations (dubbed AMOC and SMOC) had shut down. In a hot, warming world, sea ice around Antarctica held steady and then expanded northward.

I had a suspicion about a problem in ocean models. When we doubled atmospheric CO2, we found that global surface temperature after 100 years had only achieved 60 percent of its final warming. Could mixing of heat into the ocean really slow down the surface response that much? Such a long delay was not expected by the legendary Jule Charney (Hansen, 2022f).

Response function information might spur more focus on ocean mixing and on observations to test the reality of ocean mixing in all models. Such a focus on the key (real world and model) physics is analogous to how Jule Charney focused his famous investigation of climate sensitivity (Charney et al., 1979). Charney would have jumped eagerly on the issue of ocean mixing and climate response time, but he died young, in 1981.

Argo floats (Argo, 2021) dive to a two-kilometer depth, rise to the surface while making measurements, and radio the data to a satellite. Precise ocean temperatures measured by the Argo floats were the data needed to define Earth’s energy imbalance. That imbalance is important: it defines how much additional global warming is in the pipeline and it thus informs us about actions needed to stop further global warming.

Accurate determination of Earth’s energy imbalance meant that we had two major “knowns” about the climate system, the other being observed global warming in the past century. There are three major unknowns: climate sensitivity to a forcing, the net climate forcing, and the delay of surface temperature change caused by ocean mixing of heat.

Our paper also confirmed the suspicion that ocean models mixed heat into the deep ocean too efficiently, but it did not tell us why. Did models create an artificial diffusion of heat via their finite differencing approximation of the equations of motion? Did the approximations used to represent mixing on scales smaller than the model’s grid cause too much mixing? Did the coarse vertical resolution of ocean models cause excessive downward mixing?

Whatever the reason(s), excessive mixing makes it difficult to maintain a low-density ocean surface layer fed by meltwater. Therefore, SMOC and AMOC shut down more readily in the real world than in models. SMOC is more important than AMOC because SMOC shutdown accelerates Antarctic ice melt and sea level rise. The high sensitivity of SMOC implies that sea level rise could run out of control within the next few decades.

In early 2014 we reran climate simulations with our latest climate model; results were similar to those in 2006.

Prior analyses of ocean circulation focused on AMOC

That focus is understandable. Shutdown of AMOC yields large climate change in the North Atlantic with downstream impact on Europe. The reduced northward ocean heat transport also warms the Southern Ocean – an interhemispheric “seesaw” effect (Stocker, 1998). However, the research community and IPCC concluded that AMOC would not shut down this century; it would only slow down somewhat more than it has already (IPCC, 2019).

Our conclusions differed dramatically. We found that SMOC is more important than AMOC because of its effect on future sea level rise. For business-as-usual scenarios used by IPCC, we found that SMOC would shut down by midcentury (Foreword Figure 4). AMOC would also shut down this century and would not recover for centuries. Our approach to the problem also differed greatly from that of IPCC. While IPCC relies heavily on ice sheet models, our approach was based on empirical information from the real world.

How can real-world ice melt be so much faster than in the ice sheet models that IPCC relies on? Ice sheet modeling is hard. Ice sheet processes occur on spatial scales ranging from microscale freeze-thaw effects that cause pot-holes in our streets to continental-scale “rivers” of ice that discharge icebergs to the ocean. However, as argued in my “slippery slope” paper (Hansen, 2005b), the crucial amplifying feedbacks are probably interactions between ice sheets and oceans abutting against them. Our global climate model results in Ice Melt revealed such specific amplifying feedbacks.

Shutdown of SMOC is a powerful feedback

The shutdown can spur disintegration of the West Antarctic ice sheet (Foreword Figure 2). Our climate model correctly locates deep water formation along the Antarctic coast at places such as the Weddell Sea coast (section 3.8.5 in Ice Melt), which supports use of our model to study the SMOC feedback. That capability is absent in many CMIP (Climate Model Intercomparison Project) models used in the IPCC assessment (Heuze et al., 2015).

SMOC already slowed in our climate simulations by the late 20th century (Foreword Figure 4, which is Fig. 32 in Ice Melt) due to growing freshwater injection from Antarctica. Ocean current measurements are too sparse to accurately monitor SMOC, but sufficient for Purkey and Johnson (2012) to conclude that the real-world SMOC did slow during that period.

SMOC is an escape valve for ocean heat. As relatively warm water reaches the surface near Antarctica (see Foreword Figure 2), heat escapes to the air and space – especially in winter. The salty water cools there to high density and sinks, but as increasing light meltwater is added, the rate of sinking water decreases. As this surface escape valve for heat closes, that heat warms the deeper ocean, with maximum warming at 1-2 km depth. That’s the depth of ice shelf grounding lines, the part of the ice shelf that exerts strongest restraining force on landward ice [Fig. 14 of Jenkins and Doake (1991)]. West Antarctic ice shelves thus have begun to melt more rapidly (Rignot and Jacobs, 2002) and the ice streams feeding them have accelerated (Rignot, 2008).

Menviel et al. (2010) used a simplified Earth system model to show that collapse of the West Antarctic ice sheet would cause expansion of sea ice on the Southern Ocean, suppression of Antarctic Bottom Water formation, and warming of the Southern Ocean at depth. Fogwill et al. (2015) used a high-resolution atmosphere-ocean model to investigate effects of increasing freshwater flux from West Antarctica today, finding that increased ocean stratification reduced bottom water formation and increased ocean temperature at depth. Fogwill et al. submitted their paper on almost the same date in 2015 that we submitted our paper. They concluded, however, that they saw no significant atmospheric response to the freshwater injection. We found a significant accompanying atmospheric feedback.

Precipitation provides an amplifying feedback for sea level rise in our model, but a diminishing feedback in the climate models that IPCC has reported and relied on. Their models yield a large reduction of sea ice around Antarctica and increasing snowfall over the continent as Earth warms. This increased snowfall causes sea level to fall, thus at least partially offsetting sea level rise from ice sheet dynamical mass loss (Foreword Figure 2).

In our climate model described in Ice Melt, increasing meltwater cools the Southern Ocean surface enough to offset greenhouse gas warming. Indeed, the sea surface in the western portion of the Southern Ocean, where two-thirds of increased freshwater injection is occurring (Rignot et al., 2013), already has cooled while the rest of the planet has warmed (Fig. 31 in Ice Melt).

If high fossil fuel emissions continue, SMOC will shut down during the next few decades and sea ice in the Southern Ocean will expand several million square kilometers, according to our climate simulations (Foreword 4b). These effects should begin to emerge this decade from the “noise” level of unforced and unpredictable climate variability.

Before the ink had dried on our Ice Melt paper, Antarctic sea ice cover plummeted (Foreword Figure 4b) to its lowest level in 40 years of satellite data (Parkinson, 2019). Antarctic Bottom Water (AABW) formation – the engine of SMOC – increased (Silvano et al., 2020). So, was the slowdown of SMOC over the prior few decades only temporary? Will Antarctic sea ice decrease now like Arctic sea ice, as predicted by IPCC models?

No, surely not. On the contrary, data that have accumulated since we submitted our paper in 2015 allow improved assessment of the basic time scales of the climate change problem. These time scales are central to our reframing of the ice melt problem and they are at the heart of our disagreement with conclusions of IPCC. One merit of our approach is the role of empirical data, which will allow continual, easily understandable, evaluations as climate response unfolds."
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

kassy

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Re: AR6 physical science basis of climate change.
« Reply #36 on: August 15, 2021, 06:41:43 PM »
Quote
The Repercussions of a Changing Climate, in 5 Devastating Charts
https://insideclimatenews.org/news/15082021/climate-change-ipcc-charts/

Well i quite like devastating charts but do we have them?

1a is pretty good.
We talked about the hockey stick and now we live it.

Number 2 is weird. Just put that on a global map we recognize?

Number 3 is just relative  SSP trajectories so who cares.

Number 4 Sea level rise also differing by scenarios. The top right is interesting. There is quite a bit of difference in the thermal equilibrium. We have only one planet and we will only one outcome based on what we actually do in physical terms not reports.

Number 5 is just does not work. Yes stuff gets worse if the max we hit gets worse but i doubt people see these and go: oh devastating.

The first picture tells all you need to know. There is more human build stuff then natural stuff on this planet but we keep going. We have done quite a remarkable thing and we are not done.

Assuming this will work out fine is called hubris.

Also if we assume that the 50-200 CM sea level rise is an accurate range that still places a huge burden on our (grand) children. Good that we didn´t have to cope with that kind of stuff, right?
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #37 on: August 15, 2021, 06:50:56 PM »
...
Unfounded optimism is dangerous to society.

"By teaching that things are pretty much good and getting better automatically, we remove any reason for citizens to be citizens, to exercise the powers of citizenship. But that’s not how progress happens.

Nothing good happens without the collective efforts of dedicated people. History, the way it’s commonly taught, has a way of obscuring this fact." – James Loewen
“It is not the strongest or the most intelligent who will survive but those who can best manage change.”
― Leon C. Megginson

A-Team

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Re: AR6 physical science basis of climate change.
« Reply #38 on: August 16, 2021, 03:34:41 PM »
First assessment report (1990)    sci yawn (high confidence)
Second assessment report (1995)   business as usual
Third assessment report (2001)    make a pledge?
Fourth assessment report (2007)   2100 is coming!
Fifth assessment report (2014)    tsk-tsk
Sixth assessment report (2021)    more studies needed
Seventh assessment report (2028)  told you so!
Eighth assessment report (2035)   做你被告知的事
Ninth assessment report (2042)    沒有牛肉了
Tenth assessment report (2049)    事情越來越好
« Last Edit: August 16, 2021, 03:59:24 PM by A-Team »

Tor Bejnar

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Re: AR6 physical science basis of climate change.
« Reply #39 on: August 16, 2021, 04:00:46 PM »
For those less fluent (I use Google Translate):
8th: Do what you were told
9th: No more beef
10th: Things are getting better

I think things are getting better mid-century because everybody stopped complaining during the '40s.  :o
(Things are getting better, that is, for the overlords who speak, uh, Mandarin?)  :-\  :'(
Arctic ice is healthy for children and other living things.

jai mitchell

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Re: AR6 physical science basis of climate change.
« Reply #40 on: August 16, 2021, 06:19:35 PM »
Figure TS.8

2019 Temps run through an emulator that removes the near term aerosol impacts in the low-carbon scenarios and dropped to the 2000-2019 average temperature (of about 0.8C above pre-industrial).  We are currently at 1.2C above the 1850-1900 average.

Figure 4.40

How the emulator does not include the high aerosol removal temperature spikes, how the medium scenario model runs in yellow are used to obscure the low carbon model runs in blue (can you see them?)

Text from TS-55
The total earth energy imbalance measured at the top of earths atmosphere used in the AR6 model runs (it was actually more than 1.0)



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jai mitchell

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Re: AR6 physical science basis of climate change.
« Reply #41 on: August 16, 2021, 06:26:29 PM »
GISSTEMP IMAGE:
The jump in temperatures began after the end of the most recent "hiatus" in 2014

Image from peer review:
Image from The AR6 model runs were removed (selected) based on historic temperature response from the period (1981-2014)

Figure 4.11
The effect of removing the models that showed higher historic decadal warming compared to the 1981-2014 decadal warming trend (even though we had 5 years of higher temps by the time the CMIP6 was redone for AR6.  -  Note how the 2.6 SSP *JUST* was able to come in under 2C (at the end of the century)

Note: if they used the more recent, higher temperatures, then it is possible that some of the lower temp models would have been dropped as well as adding the higher temp models so this model mean would have shifted up a bit.


« Last Edit: August 16, 2021, 07:01:37 PM by jai mitchell »
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A-Team

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Re: AR6 physical science basis of climate change.
« Reply #42 on: August 16, 2021, 08:44:01 PM »
AR1 -- 31 years ago -- actually had quite decent scientific coverage of methane.  The report could have been written yesterday with only minor edits. Enough was reliably known back then to take action but nothing has been done in the intervening years. There is no plan to do anything now even though methane levels have skyrocketed.

AR1 even noted that oil fields simply vented unwanted methane instead of flaring it off to CO2, pg 21. It's been shown by CarbonMapper that high pressure venting is still a widespread practice today in the Permian Basin (tallied as 'intermittent' sources). In other words, fixing leaking pipelines or capping old wells just doesn't cut it.

Taking the half life of CH4 in the atmosphere at 9.1 years implies that of 9 molecules released back in 1990, 1 would still remain there. Most of the carbon atoms are now in CO2 still trapping outgoing heat.

Perhaps an atom or two have been taken up by a tree or southern ocean. But the tree would have been burned down by now to make cattle pasture in Brazil, or logged off in BC by private equity to make lumber for Obama's McMansion, or pulped to make newsprint for humvee ads, or shipped to Germany as phony green fuel pellets despite it having been sold to an airline passenger to offset flight emissions.

A few of the 198 occurrences of word 'methane' in the 362 page report are extracted below. (The report has long been “out of print” but a poor quality OCR scan is still online).

CLIMATE CHANGE The IPCC Scientific Assessment Report 1990
https://www.ipcc.ch/site/assets/uploads/
2018/03/ipcc_far_wg_I_full_report.pdf     

EXECUTIVE SUMMARY We are certain of the following:

Emissions resulting from human activities are substantially increasing the atmospheric concentrations of the greenhouse gases carbon dioxide, methane, chlorofluorocarbons (CFCs) and nitrous oxide.

These increases will enhance the greenhouse effect, resulting on average in an additional warming of the Earth's surface.

The main greenhouse gas, water vapour, will increase in response to global warming and further enhance it.

The long-lived gases would require immediate reductions in emissions from human activities of over 60% to stabilize their concentrations at today's levels, methane would require a 15-20% reduction.

Methane concentrations have moie than doubled because of rice production, cattle reanng, biomass burning, coal mining, and ventilation of natural gas. Also fossil fuel combustion may have also contributed through chemical reactions in the atmosphere which reduce the rate ol removal of methane.

Higher temperatures could increase the emissions of methane at high northern latitudes from decomposable organic matter trapped in permafrost and methane hydrates.

In the Business-as-Usual scenario (Scenario A) the energy supply is coal intensive and on the demand side only modest efficiency increases are achieved. Carbon monoxide controls are modest, deforestation continues until the tropical forests are depleted and agricultural emissions of methane and nitrous oxide are uncontrolled.

Methane emissions from enteric fermentation in ruminant animals including all cattle, sheep and wild animals is estimated to provide an atmospheric source ot 65 - 100 Tg CH4 per year (Crutzen 1986, Lcrner/1988).

Methane emissions depend upon animal populations as well as the amount and type of food It is difficult to estimate the change in this source over the last century accurately because the significant increase in the number of cattle and sheep has been partially offset by decreases in the populations of elephants and North American bison.

One estimate suggests that the magnitude of this source has increased from 21 Tg CH4 per year in 1890 to 78 Tg CH4 per year in 1983 (Crutzen 1986).

Methane production by domestic animals, wild ruminants, other herbivorous fauna, and humans
PJ Crutzen, I Aselmann, W Seiler
https://onlinelibrary.wiley.com/doi/epdf/10.1111/j.1600-0889.1986.tb00193.x
« Last Edit: August 16, 2021, 10:50:43 PM by A-Team »

vox_mundi

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Re: AR6 physical science basis of climate change.
« Reply #43 on: August 16, 2021, 09:00:41 PM »
“There are three classes of people: those who see. Those who see when they are shown. Those who do not see.” ― anonymous

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

Sciguy

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Re: AR6 physical science basis of climate change.
« Reply #44 on: August 16, 2021, 11:01:02 PM »
Focussing on the dire climate scenarios leads to feelings of anxiety, depression and inaction.  This is what the fossil fuel companies want.  The way to combat that is to inspire hope and calls for action.

https://www.verywellhealth.com/climate-anxiety-hope-and-action-5192818

Quote
How to Soothe Climate Anxiety With Hope and Action
Sarah Simon
July 19, 2021

Quote
But pessimism can actually hurt efforts for change.

"I would like people to stop talking about the apocalypse as inevitable, and to stop framing it all as negative," Ray says. "The way climate change is talked about, even at a very young age, is so damaging. It itself is part of the problem."

The Dangers of Ignoring Climate Anxiety

When psychologists talk about anxiety, they might say that it can be both adaptive and maladaptive. But to avoid harming each other and the environment, even more, Ray says, we're going to have to cope with climate anxiety in an adaptive way.

jai mitchell

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Re: AR6 physical science basis of climate change.
« Reply #45 on: August 17, 2021, 01:45:47 AM »
oh! so that is why we haven't had any real effective climate policy put into place so far?  We weren't looking on the bright side!!!
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kassy

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Re: AR6 physical science basis of climate change.
« Reply #46 on: August 17, 2021, 01:56:49 AM »
I am pretty sure that is actually a deep plant by fossil fuel companies so you can claim it is all ok.

Neither anxiety or depression have any meaningful physical relation.
Inaction is what we practiced the last few decades and that did not help.

We need a rate of change no one is prepared to accept. We cannot keep doing what we do. Being positive is nice but maybe also acknowledge that when the AR6 report was published the US called on OPEC to drill more oil.
We have an unsustainable growth problem which happens whichever way you vote which should lead to anxiety and depression.

Probably it is best to focus on the inaction and do something.
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FishOutofWater

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Re: AR6 physical science basis of climate change.
« Reply #47 on: August 17, 2021, 03:38:17 AM »
Focusing on the optimistic scenarios leads to delay and inaction.

Focussing on the dire climate scenarios leads to feelings of anxiety, depression and inaction.  This is what the fossil fuel companies want.  The way to combat that is to inspire hope and calls for action.

Heads they win, tails we lose. Look on the bright side of life.

Sciguy

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Re: AR6 physical science basis of climate change.
« Reply #48 on: August 17, 2021, 08:12:24 AM »
Dr. Michael Mann (of hockey stick fame) and others are fighting back against doomerism that leads to inaction:

https://www.theguardian.com/comment is free/2021/may/01/climate-change-environment-hope-future-optimism-success

Quote
The climate scientist Michael Mann takes these people on – he calls them inactivists and doomists – in his recent book The New Climate Wars, which describes the defeatism that has succeeded outright climate denial as the great obstacle to addressing the crisis. He echoes what Carbon Tracker asserted, writing: “The solution is already here. We just need to deploy it rapidly and at a massive scale. It all comes down to political will and economic incentives.” The climate scientist Diana Liverman shares Mann’s frustration. She was part of the international team of scientists who authored the 2018 “hothouse Earth” study whose conclusions were boiled down, by the media, into “we have 12 years”.

The report, she regularly points out, also described what we can and must do “to steer the Earth System away from a potential threshold and stabilize it in a habitable interglacial-like state. Such action entails stewardship of the entire Earth System – biosphere, climate, and societies – and could include decarbonization of the global economy, enhancement of biosphere carbon sinks, behavioral changes, technological innovations, new governance arrangements, and transformed social values.” It was a warning but also a promise that if we did what science tells us we must, we would not preserve the current order but form a better one.

Another expert voice for hope is Christiana Figueres, who as executive secretary of the United Nations framework convention on climate change negotiated the Paris climate accords in 2015. As she recently declared: “This decade is a moment of choice unlike any we have ever lived. All of us alive right now share that responsibility and that opportunity. The optimism I’m speaking of is not the result of an achievement, it is the necessary input to meeting a challenge. Many now believe it is impossible to cut global emissions in half in this decade. I say, we don’t have the right to give up or let up.” She speaks of how impossible a treaty like the one she negotiated seemed after the shambles at the end of the 2009 Copenhagen meeting.

TeaPotty

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Re: AR6 physical science basis of climate change.
« Reply #49 on: August 17, 2021, 10:50:34 AM »
Unfounded optimism is dangerous.
Calling reality "doomerism" is projection, showing emotional immaturity, and a deeply flawed worldview/philosophy disconnected from reality that many don't want to let go of.

The argument that sharing facts causing distress, results in inaction, is an insane idea, that bears no weight when viewed through the lens of history and human nature.

Despair is the biggest driver of change in mankind.
Meaning, changing circumstances force humans to adapt, and those who looked ahead adapted better. Its as simple as that.

You don't think to yourself "its fine" when racing towards a wall, you calculate your exit opportunities. 40+ years of "its gonna be fine" has not yielded any significant climate action AT ALL. How about some reflection?

Man's nature is to do as little as needed, for as long as possible. Setting higher goals is a personal challenge. So telling others "everything will be fine" just breeds complacence and inaction. Its simple human nature, and denying it is hubris.
« Last Edit: August 17, 2021, 11:27:01 AM by TeaPotty »