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GeoffBeacon

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Methane emissions, sea levels and temperature
« on: July 10, 2020, 09:35:44 PM »
Reasons for cutting methane emissions No 1: Sea level rise

Methane concentrations in the atmosphere cause a sizable proportion of climate forcing. (58% of CO2 forcing, IPCC AR5).  This forcing heats the Earth causing a rise in Earth's heat content.

Methane has a short lifetime, with half life of 9.1 years. After it decays the Global Mean Surface Temperature (GMST) soon reverts to a value which does not contain much impact from methane's warming because the temporary "methane heat" in the surface layers is radiated into space.

According to IPCC AR5 (WG1 SPM), 90% of the "methane heat" remains, as Ocean Heat Content (OHC) [including the latent heat difference between ice mass and melt water?]. This remaining heat dissipates over a few centuries.

Increased OHC and melting land ice are the main drivers of increasing Global Mean Sea Level (GMSL).

Since methane is a significant part of current climate forcing, it is also a significant part of OHC and land ice melting: It is a significant part of increasing GMSL.

The long-lived part of the heat from methane forcing is thus a large proportion of increasing GMSL.

In short,

The rise in GMST from methane currently in the atmosphere lasts decades or so.
The rise in GMSL from methane currently in the atmosphere lasts a century or more.


Is this well understood? Did the Small Island Developing States miss this point when they pushed for a temperature limit. Crudely:

Quote
Methane emissions & Small Island Developing States (SIDS)

SIDS asked for a limit on GMST of 1.5C to limit sea levels.

Methane is short-lived with a short-lived effect on GMST.
    … Its effect on peak GMST is only significant near peak.

But, methane heating increases sea level for centuries.

The SIDS got the wrong target …
          Methane emissions will help to drown them.

 

Should cutting methane now be a top prioity?


Reasons for cutting methane emissions No 2: Its effects are quick and so buys time
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kassy

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Re: Methane emissions, sea levels and temperature
« Reply #1 on: July 10, 2020, 10:54:46 PM »
Could you add some links like for:
According to IPCC AR5 (WG1 SPM), 90% of the "methane heat" remains, as Ocean Heat Content (OHC) [including the latent heat difference between ice mass and melt water?]. This remaining heat dissipates over a few centuries.

And the SIDS quote.

Thanks!
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GeoffBeacon

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Re: Methane emissions, sea levels and temperature
« Reply #2 on: July 11, 2020, 01:35:19 AM »
Kassy, Thanks I meant to follow up with references but got distracted.


Methane forcing is 58% of CO2 forcing calculated from numbers in Figure SPM.5
IPCC AR5, WG1,Summaryfor Policymakers

Methane has ... a half life of 9.1 years
Wikipedia

Quote
Ocean warming dominates the increase in energy stored in the climate system, accounting
for more than 90% of the energy accumulated between 1971 and 2010 (high confidence).
IPCC AR5, WG1,Summaryfor Policymakers

Quote
It is very likely that there is a substantial anthropogenic contribution to the global mean sea level rise since the 1970s. This is based on the high confidence in an anthropogenic influence on the two largest contributions to sea level rise, that is thermal expansion and glacier mass loss.
IPCC AR5, WG1,Summaryfor Policymakers

Also ...

Centuries of thermal sea-level rise due to anthropogenic emissions of short-lived greenhouse gases.

Increased importance of methane reduction for a 1.5 degree target

Very Strong Atmospheric Methane Growth in the 4 Years 2014–2017: Implications for the Paris Agreement

Am I right in thinking that it is commonly believed that limiting GMST is THE means of limiting sea level rise - and as methane is less important for peak GMST, it can't be important for sea level?

This belief is surely false.
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GeoffBeacon

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Re: Methane emissions, sea levels and temperature
« Reply #3 on: July 12, 2020, 02:01:20 PM »
I'm trying to write a piece for my blog about the lack of appreciation of this problem.

Methane's heating effect on sea-level is very different to its effect on global temperature.
It is much more worrying.

I think it's unknown to many, especially policy makers.

Am I wrong?
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GeoffBeacon

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Re: Methane emissions, sea levels and temperature
« Reply #4 on: July 13, 2020, 08:51:03 PM »
Just posted: Cut methane emissions soon, Sea level, methane and a false assumption

I'd still like to know if anyone agrees/disagrees.
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Ken Feldman

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Re: Methane emissions, sea levels and temperature
« Reply #5 on: July 13, 2020, 11:34:32 PM »
While the IPCC SR1.5 didn't make it super-clear, they did discuss this issue in brief.  The reference that I bolded discusses the same issue for CO2.

https://www.ipcc.ch/sr15/chapter/chapter-3/

Quote
3.6.3.2
Sea level

Policy decisions related to anthropogenic climate change will have a profound impact on sea level, not only for the remainder of this century but for many millennia to come (Clark et al., 2016). On these long time scales, 50 m of sea level rise (SLR) is possible (Clark et al., 2016). While it is virtually certain that sea level will continue to rise well beyond 2100, the amount of rise depends on future cumulative emissions (Church et al., 2013) as well as their profile over time (Bouttes et al., 2013; Mengel et al., 2018) . Marzeion et al. (2018) found that 28–44% of present-day glacier volume is unsustainable in the present-day climate and that it would eventually melt over the course of a few centuries, even if there were no further climate change. Some components of SLR, such as thermal expansion, are only considered reversible on centennial time scales (Bouttes et al., 2013; Zickfeld et al., 2013) , while the contribution from ice sheets may not be reversible under any plausible future scenario (see below).




Ken Feldman

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Re: Methane emissions, sea levels and temperature
« Reply #6 on: July 13, 2020, 11:58:44 PM »
The IPCC Special Report on the Oceans and Cryosphere covers this topic in section 4.2.3.5 and includes the reference on short lived greenhouse gases (Zickfeld et. al., 2017).

https://www.ipcc.ch/srocc/chapter/chapter-4-sea-level-rise-and-implications-for-low-lying-islands-coasts-and-communities/

Quote
Beyond the 21st century, the relative importance of the long-term contributions of the various components of SLR changes markedly. For glaciers, the long-term is of limited importance, because the sea level equivalent of all glaciers is restricted to 0.32 ± 0.08 m when taking account of ice mass above present day sea level (Farinotti et al., 2019). Hence, there is high confidence that the contribution of glaciers to SLR expressed as a rate will decrease over the 22nd century under RCP8.5 (Marzeion et al., 2012). For thermal expansion the gradual rate of heat absorption in the ocean will lead to a further SLR for several centuries (Zickfeld et al., 2017).
...

Ken Feldman

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Re: Methane emissions, sea levels and temperature
« Reply #7 on: July 14, 2020, 12:48:19 AM »
The European Union is formulating policies to address methane emissions.

https://www.spglobal.com/platts/en/market-insights/latest-news/natural-gas/071320-ec-consults-on-methane-leaks-in-push-to-clean-up-eu-gas-imports

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EC consults on methane leaks in push to clean up EU gas imports
13 Jul 2020
Siobhan Hall

Brussels — The European Commission is seeking views on how to reduce leaks of potent greenhouse gas methane from oil, gas and agricultural sectors as part of the EU's efforts to become climate-neutral by 2050.

Most of the methane leaks from fossil gas production and transport happen before the natural gas or LNG reaches the EU, so a new EU policy on methane emissions could have far-reaching impacts on the global gas market.

Quote
The key challenge is how to improve measuring, reporting and verifying emissions at the level of private entities, it said.

On average, 5% of sources account for 50% of the leaks, known as "super-emitters".

Leak detection and repair programs, as well as finding and addressing these "super-emitters, can be a very effective action," the EC said.

kassy

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Re: Methane emissions, sea levels and temperature
« Reply #8 on: July 14, 2020, 02:48:10 PM »
Just posted: Cut methane emissions soon, Sea level, methane and a false assumption

I'd still like to know if anyone agrees/disagrees.
Interesting post .

Never thought of it that way.

Basically that provides another reason to cut what methane emissions we can a.s.a.p.

But of course  we should already do that because we are probably already committed to a bad outcome.

Quote
while the contribution from ice sheets may not be reversible under any plausible future scenario (see below).

vs (or maybe just and...)

‘Teetering at the edge’: Scientists warn of rapid melting of Antarctica’s ‘Doomsday glacier’
Thwaites glacier is losing ice at an accelerating rate, threatening catastrophic sea-level rise

...

“The big question is how quickly it becomes unstable. It seems to be teetering at the edge,” Paul Cutler, programme director for Antarctic glaciology at America’s National Science Foundation told the Financial Times this week.

...

https://www.independent.co.uk/environment/thwaites-glacier-antarctic-melting-doomsday-climate-a9616966.html

Recent research shows that after we hit reductions of CO2 we still have 15 years of land warming. For seas there is often a 40 year lag. Not sure if it is applicable to CDW but if you figure in a 40 year delay then the damage done now is from 1980.

And the eventual peak we committed too is at least this year.


 
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Ken Feldman

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Re: Methane emissions, sea levels and temperature
« Reply #9 on: July 14, 2020, 08:05:48 PM »
The linked study provides a good assessment of our ability to reduce methane emissions over the next few decades.

https://iopscience.iop.org/article/10.1088/2515-7620/ab7457

Quote
Lena Höglund-Isaksson et al 2020 Environ. Res. Commun. 2 025004
Technical potentials and costs for reducing global anthropogenic methane emissions in the 2050 timeframe –results from the GAINS model

Abstract

Methane is the second most important greenhouse gas after carbon dioxide contributing to human-made global warming. Keeping to the Paris Agreement of staying well below two degrees warming will require a concerted effort to curb methane emissions in addition to necessary decarbonization of the energy systems. The fastest way to achieve emission reductions in the 2050 timeframe is likely through implementation of various technical options. The focus of this study is to explore the technical abatement and cost pathways for reducing global methane emissions, breaking reductions down to regional and sector levels using the most recent version of IIASA's Greenhouse gas and Air pollution Interactions and Synergies (GAINS) model. The diverse human activities that contribute to methane emissions make detailed information on potential global impacts of actions at the regional and sectoral levels particularly valuable for policy-makers. With a global annual inventory for 1990–2015 as starting point for projections, we produce a baseline emission scenario to 2050 against which future technical abatement potentials and costs are assessed at a country and sector/technology level. We find it technically feasible in year 2050 to remove 54 percent of global methane emissions below baseline, however, due to locked in capital in the short run, the cumulative removal potential over the period 2020–2050 is estimated at 38 percent below baseline. This leaves 7.7 Pg methane released globally between today and 2050 that will likely be difficult to remove through technical solutions. There are extensive technical opportunities at low costs to control emissions from waste and wastewater handling and from fossil fuel production and use. A considerably more limited technical abatement potential is found for agricultural emissions, in particular from extensive livestock rearing in developing countries. This calls for widespread implementation in the 2050 timeframe of institutional and behavioural options in addition to technical solutions.

This article summarizes the study:

https://ensia.com/notable/methane-greenhouse-gas-climate-change/

Quote
Three workable strategies for putting a big dent in methane, the “other” greenhouse gas
April 16, 2020
Andrew Urevig

Quote
Improve Waste Management

Yard waste and uneaten food decomposing in landfills vent methane into the air, so the study finds lots of potential in improved garbage management. The researchers estimate that separating waste by source, with better recycling and schemes to capture energy from some trash — plus a ban on organic waste in landfills — could help the world avoid emitting 778 million metric tons (858 million tons) of methane that would otherwise make its way into the air between now and 2050.

Quote
Repair Leaks

Ultimately, fossil fuels will also need to be phased out, Höglund Isaksson writes. But in the meantime, the study finds that we could slow the growth of methane emissions by taking steps such as implementing programs to detect and repair leaks in oil production and the extraction and transportation of natural gas. Coal mines could consistently implement degasification and improve ventilation, and oil drillers could try to recover associated gas. Such steps — with leakage detection and repair being the biggest — could prevent 2.35 billion metric tons (2.57 billion tons) of methane emissions by 2050.

Quote
Modify Agricultural Practices

Methane emissions from agriculture, the study finds, will be the hardest area for technical improvements. Rice cultivation’s footprint could decrease if farmers used alternative hybrids, improved water management and added materials to improve soil properties. These steps could avoid 335 million metric tons (370 million tons) of emitted methane by 2050. Livestock breeders could continue efforts to raise more productive animals: If farmers could use fewer cows to produce the same amount of milk, for example, that would cut back on emissions. This approach could yield different emissions results in cows, pigs, sheep and other livestock.

GeoffBeacon

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Re: Methane emissions, sea levels and temperature
« Reply #10 on: July 15, 2020, 01:32:12 AM »
Thank you, Ken Feldman and kassy for those very helpful comments.

IPCC SR15, did address, sea-level rise, as you say, Ken - but probably not enough.

However, it didn't seem to bring out the long-term effect on sea-level of methane's short-term heating.

Also, this whole UNFCCC/IPCC process doesn't seem to have considered the benefits of a couple of decades of a slightly cooler Earth in the time before a peak temperature is reached.

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Ken Feldman

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Re: Methane emissions, sea levels and temperature
« Reply #11 on: July 15, 2020, 10:08:59 PM »
James Hansen wrote a paper that emphasized the benefits of decreasing methane concentrations in the short term while we worked on bringing down CO2 (a much harder task).  I can't find it thought (he's written a ton of papers).

Ken Feldman

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Re: Methane emissions, sea levels and temperature
« Reply #12 on: July 16, 2020, 08:40:25 PM »
^^^
Found the paper.  It was published in PNAS in 2004.

https://pubs.giss.nasa.gov/docs/2004/2004_Hansen_ha04010t.pdf

Quote
Greenhouse gas growth rates
James Hansen* and Makiko Sato

We posit that feasible reversal of the growth of atmospheric CH4 and other trace gases would provide a vital contribution toward averting  dangerous  anthropogenic  interference  with  global  cli-mate. Such trace gas reductions may allow stabilization of atmospheric CO2 at an achievable level of anthropogenic CO2 emissions, even if the added global warming constituting dangerous anthropogenic  interference  is  as  small  as  1°C.  A  1°C  limit  on  global warming, with canonical climate sensitivity, requires peak CO2 ~440 ppm if further non-CO2 forcing is ~0.5 W/m2, but peak CO2 ~520 ppm if further non-CO2 forcing is ~0.5 W/m2. The practical result is that a decline of non-CO2 forcings allows climate forcing to be stabilized with a significantly higher transient level of CO2 emissions. Increased ‘‘natural’’ emissions of CO2, N2O, and CH4 are expected  in  response  to  global  warming.  These  emissions,  an indirect  effect  of  all  climate  forcings,  are  small  compared  with human-made climate forcing and occur on a time scale of a few centuries,  but  they  tend  to  aggravate  the  task  of  stabilizing atmospheric composition.

Quote
We have suggested (13) that a concerted effort to reduce CH4 emissions could yield a negative forcing, which would be amplified ~40% by the indirect effects of CH4 on stratospheric H2O and tropospheric O3. CH4by itself could yield a forcing change of ~0.25 W/m2 if it were reduced from today’s 1,755 ppb to 1,215 ppb, which would require reducing anthropogenic CH4 emissions by 40–50% (ref. 14 and Drew Shindell, personal communication). Conversely, CH4 could provide large positive forcing if emissions grow, e.g.,CH4 increases to 3,140 ppb in 2100 in the IPCC (3) IS92a scenario,yielding ~0.5 W/m2 forcing.

Ken Feldman

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Re: Methane emissions, sea levels and temperature
« Reply #13 on: July 22, 2020, 08:16:35 PM »
The linked article about the differences between the short-term and long-term global warming potentials of methane indicates that focusing exclusively on methane reductions at the expense of reducing carbon dioxide emissions results in higher long term temperature increases.

https://iopscience.iop.org/article/10.1088/1748-9326/ab6d7e/pdf

Quote
Demonstrating GWP*: a means of reporting warming-equivalent emissions that captures the contrasting impacts of short- and long-lived climate pollutants
John Lynch et al 2020 Environ. Res. Lett.15 044023

Abstract
The atmospheric lifetime and radiative impacts of different climate pollutants can both differ markedly, so metrics that equate emissions using a single scaling factor, such as the 100-year Global Warming Potential (GWP100), can be misleading. An alternative approach is to report emissions as ‘warming-equivalents’ that result in similar warming impacts without requiring a like-for-like weighting per emission. GWP*, an alternative application of GWPs where the CO2-equivalence of short-lived climate pollutant emissions is predominantly determined by changes in their emission rate, provides a straightforward means of generating warming-equivalent emissions. In this letter we illustrate the contrasting climate impacts resulting from emissions of methane, a short-lived greenhouse gas, and CO2, and compare GWP100 and GWP* CO2-equivalents for a number of simple emissions scenarios. We demonstrate that GWP* provides a useful indication of warming, while conventional application of GWP100 falls short in many scenarios and particularly when methane emissions are stable or declining, with important implications for how we consider ‘zero emission’ or ‘climate neutral’ targets for sectors emitting different compositions of gases. We then illustrate how GWP* can provide an improved means of assessing alternative mitigation strategies. GWP*allows warming-equivalent emissions to be calculated directly from CO2-equivalent emissions reported using GWP100, consistent with the Paris Rulebook agreed by the UNFCCC, on condition that short-lived and cumulative climate pollutants are aggregated separately, which is essential for transparency. It provides a direct link between emissions and anticipated warming impacts, supporting stocktakes of progress towards a long-term temperature goal and compatible with cumulative emissions budgets

Quote
We can demonstrate the utility of multi-gas cumulative CO2-w.e. totals in a decision making context by considering how they would describe alternative mitigation pathways, as infigure8. In this scenario, the emissions of one gas cease in year 50, and then the emissions of the remaining gas in year 100. Stopping methane first results in a large initial reversal of recent warming, but temperatures then start to rise again due to the ongoing CO2 emissions. Temperature then stabilises at the temperature reached in year 100 when CO2 emissions are also stopped. Stopping CO2 first,we see that the rate of warming declines, and then when methane emissions stop in year 100 we have a significant reversal of warming, stabilising at a lower long-term temperature than in the methane-first scenario. Cumulative CO2-w.e. provides a clear indication of these dynamics, while cumulative CO2e suggests either strategy would lead to the same response, but which represents neither scenario.

prokaryotes

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Re: Methane emissions, sea levels and temperature
« Reply #14 on: July 23, 2020, 09:55:42 PM »
The Climate & Clean Air Coalition discusses Short Lived Climate Pollutants (SLCP), including methane, often in the context of the Sustainable Development Goals framework.  https://www.youtube.com/c/ClimateCleanAirCoalition/videos
CLIMATE STATE WEBSITE | YOUTUBE | VIMEO | TWITTER

GeoffBeacon

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Re: Methane emissions, sea levels and temperature
« Reply #15 on: July 29, 2020, 07:38:37 AM »
Ken Feldman,

Thanks for mentioning the article by Lynch et al. It is a good example of what worries me.

It addresses the peak temperature target of the Paris Agreement and avoids an issue that may be important. An example ...
Quote
Imagine two scenarios, which stay within the 1.5C limit:

(A) Global surface temperature rises to the 1.5C limit immediately and remains there until 2100.

(B) Global surface temperature rises steadily to 1.5C just reaching 1.5C  in 2100.

Both are Compliant with the Paris Agreement.
(A) heats  the Earth more than (B).

Is the difference important?

-------

Lynch et al. say
Quote
Sustained SLCP emissions result in stable forcing. Eventually, if maintained indefinitely,this results in no additional warming

Surely they mean "no additional rise in the Global Mean Surface Temperature (GMST)".

Not the same thing as "no additional warming"

What are the other differences?

Sea-level rise?

Feedbacks triggered?
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Ken Feldman

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Re: Methane emissions, sea levels and temperature
« Reply #16 on: July 29, 2020, 06:35:28 PM »
Ken Feldman,

Thanks for mentioning the article by Lynch et al. It is a good example of what worries me.

It addresses the peak temperature target of the Paris Agreement and avoids an issue that may be important. An example ...
Quote
Imagine two scenarios, which stay within the 1.5C limit:

(A) Global surface temperature rises to the 1.5C limit immediately and remains there until 2100.

(B) Global surface temperature rises steadily to 1.5C just reaching 1.5C  in 2100.

Both are Compliant with the Paris Agreement.
(A) heats  the Earth more than (B).

Is the difference important?

-------

Lynch et al. say
Quote
Sustained SLCP emissions result in stable forcing. Eventually, if maintained indefinitely,this results in no additional warming

Surely they mean "no additional rise in the Global Mean Surface Temperature (GMST)".

Not the same thing as "no additional warming"

What are the other differences?

Sea-level rise?

Feedbacks triggered?

In a simple energy balance model, no changes in forcings would result in stable energy exchanges and no increase in temperatures.  In reality, there would be interannual variations in temperatures and forcings due to natural release of GHGs and variations in sinks.  However, temperatures wouldn't vary too much from the long term average once it stabilizes.

Our goal though would be to decrease the forcings over time and bring the temperatures down to avoid losing too much of the Greenland and Antarctic ice sheets.  If West Antarctica starts to collapse due to marine ice sheet instability, sea levels will continue to increase by multi-meter amounts per century.  For comparison, they're currently increasing about 38 cm per century, and that's already causing problems.

kassy

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Re: Methane emissions, sea levels and temperature
« Reply #17 on: July 29, 2020, 07:15:55 PM »
A vs B

No because A is not really happening and B is bad enough and is also not happening.

We will C which means overshooting 1,5 and then stabilizing some time later but all that before 2100.

Quote
Our goal though would be to decrease the forcings over time and bring the temperatures down to avoid losing too much of the Greenland and Antarctic ice sheets.

If we are really honest we have to admit that 1C with no overshoot might have worked.

If the world had aimed for 1C with max overshoot of 1.5C we could still be where we are now. So about to lose the arctic ice in a decade or two and the permafrost being a source not a sink since early this century.

The situation in Antarctica also deteriorated the recent years and it is not certain we can stop this process at all.

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Re: Methane emissions, sea levels and temperature
« Reply #18 on: July 29, 2020, 11:44:51 PM »
Thanks kassy & Ken.

Ken  you may be right saying

Quote
"Our goal though would be to decrease the forcings over time and bring the temperatures down to avoid losing too much of the Greenland and Antarctic ice sheets"

But that obscures the point I am making.

Less than 10% of the heat from a short period of forcing is stored on the surface. This heat  dissipates in a few years.

About 90% of the heat from the same short period of forcing is stored as ocean heat content. This heat dissipates slowly over centuries so heating from short lived agents (esp methane) increases ocean temperatures for centuries.

You are right in saying "no changes in forcings would result in stable energy exchanges and no increase in temperatures". That's when the Earth reaches equilibrium but the Earth is many centuries from equilibrium.

In the case of surface temperatures, your explanation more-or-less holds because the Earth's surface radiates to space fairly quickly - but this leaves 90% of the heat in the ocean.

Ocean heat is increasing much quicker than any heat at the Earth's surface where Global Mean Surface Temperature (GMST) is measured.

Warmer seas cause more ice melt. Isn't that a worry in the Arctic and more recently in Antarctica?

Speeding up ice melt causes feedbacks due to changes in albedo.

I worry about other feedbacks too.

What is happening to subsurface temperatures in the Arctic Tundra, for example?
 
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Ken Feldman

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Re: Methane emissions, sea levels and temperature
« Reply #19 on: July 30, 2020, 12:00:08 AM »
Eventually the heat stored in the deep ocean comes back to the surface.  If we can lower the greenhouse gas concentrations in the atmosphere before it comes back to the surface, the stored heat can radiate out to space when the warmer water upwells to the surface.

Only a small portion of the warm water comes into contact with the ice sheets.  Most of it circulates around the globe for centuries.

Here are a couple of studies that discuss the Southern Ocean (where most of the excess heat gets stored) and how it interacts with the Antarctic Ice Sheet.

https://www.researchgate.net/profile/David_Holland4/publication/340045916_The_Southern_Ocean_and_its_interaction_with_the_Antarctic_Ice_Sheet/links/5e7c9599299bf1a91b7af9d0/The-Southern-Ocean-and-its-interaction-with-the-Antarctic-Ice-Sheet.pdf

Quote
The Southern Ocean and its interaction with the Antarctic Ice Sheet
David M. Holland, Keith W. Nicholls and Aurora Basinski
DOI: 10.1126/science.aaz5491 (6484), 1326-133

The Southern Ocean exerts a major influence on the mass balance of the Antarctic Ice Sheet, eitherindirectly, by its influence on air temperatures and winds, or directly, mostly through its effects on iceshelves. How much melting the ocean causes depends on the temperature of the water, which in turn is controlled by the combination of the thermal structure of the surrounding ocean and local ocean circulation, which in turn is determined largely by winds and bathymetry. As climate warms and atmospheric circulation changes, there will be follow-on changes in the ocean circulation and temperature. These consequences will affect the pace of mass loss of the Antarctic Ice Sheet.

https://tos.org/oceanography/article/southern-ocean-warming

Quote
Sallée, J.-B. 2018. Southern Ocean warming.
Oceanography 31(2):52–62, https://doi.org/10.5670/oceanog.2018.215.

Article Abstract

The Southern Ocean plays a fundamental role in global climate. With no continental barriers, it distributes climate signals among the Pacific, Atlantic, and Indian Oceans through its fast-flowing, energetic, and deep-reaching dominant current, the Antarctic Circumpolar Current. The unusual dynamics of this current, in conjunction with energetic atmospheric and ice conditions, make the Southern Ocean a key region for connecting the surface ocean with the world ocean’s deep seas. Recent examinations of global ocean temperature show that the Southern Ocean plays a major role in global ocean heat uptake and storage. Since 2006, an estimated 60%–90% of global ocean heat content change associated with global warming is based in the Southern Ocean. But the warming of its water masses is inhomogeneous. While the upper 1,000 m of the Southern Ocean within and north of the Antarctic Circumpolar Current are warming rapidly, at a rate of 0.1°–0.2°C per decade, the surface sub­polar seas south of this region are not warming or are slightly cooling. However, subpolar abyssal waters are warming at a substantial rate of ~0.05°C per decade due to the formation of bottom waters on the Antarctic continental shelves. Although the processes at play in this warming and their regional distribution are beginning to become clear, the specific mechanisms associated with wind change, eddy activity, and ocean-ice interaction remain areas of active research, and substantial challenges persist to representing them accurately in climate models.


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Re: Methane emissions, sea levels and temperature
« Reply #20 on: July 30, 2020, 07:01:19 AM »
Thank Ken.

That's very informative.
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