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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #150 on: September 28, 2021, 10:40:56 PM »
Using values from AR6 (see the attached image) Gavin Schmidt endorses the pursuit of rapidly reducing methane emissions.  However, I note that his same conclusion could easily have been made using values AR5, but since 2007 methane concentrations in the atmosphere have been growing not slowing.  So why should anyone believe that policy makers will take the AR6 findings about methane any more seriously than they took the AR5 findings on methane?

Title: "The definitive CO2/CH4 comparison post"

https://www.realclimate.org/index.php/archives/2021/09/the-definitive-co2-ch4-comparison-post/

Extract: "First of all, let’s be clear about the relative magnitude of the gas concentrations. In 2020, CO2 was at ~410 parts per million, while CH4 was around 1870 parts per billion (or 1.87 ppm, a factor of more than 200 smaller). However the relative rise since the pre-industrial is three times larger for CH4, around 150%, compared to the 50% increase in CO2.

The radiative forcing from these changes in concentrations can be easily calculated using standard formulas (from Etminan et al, 2016 which supersede the slightly simpler ones from IPCC TAR), as about 2 W/m2 for the CO2 change and 0.65 W/m2 for CH4.

But methane’s role in atmospheric chemistry and as a source of stratospheric water vapour means that it has a bigger effect on climate than just the direct effect of its concentration. Methane emissions have a feedback on its own lifetime, serve as an ozone precursor, and reduce the production of sulphate and nitrate aerosols (and consequently indirect cloud-aerosol effects), all of which amplify its net warming effect to about 1.2 W/m2 (to about 60% of the CO2 effect since 1750). There is also a very small impact of the CH4 oxidation to CO2 itself for any fossil-fuel derived methane.

This implies that if you convert the impacts of each set of emissions into temperatures, as was done in the IPCC AR6 report, you get about 0.75ºC from the changes in CO2 and 0.5ºC for CH4 (from the late 19th C, see figure below) or 1ºC and 0.6ºC, respectively, from 1750. Thus despite the smaller concentrations and changes in methane compared to carbon dioxide, the impacts are comparable.

Whatever way you slice this it implies that CH4 reductions have an outsize effect on climate, as well as an undeniably positive impact on air pollution, crop yields and public health (mainly through ozone reductions). It is therefore not a complicated decision to pursue methane reductions, taking care not to assume that doing so gets you off the hook for reducing CO2, whatever the EPA says."
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #151 on: September 29, 2021, 05:33:51 PM »
The linked reference and associated linked article suggest that the Pine Island Ice Shelf could well collapse in the next decade, or two, without any hydrofracturing required.  This raises the risk of the WAIS collapsing in the coming decades (versus the AR6 assumptions that err on the side of least drama).

Joughin, I., et al. (11 Jun, 2021), "Ice-shelf retreat drives recent Pine Island Glacier speedup", SCIENCE ADVANCES, Issue 24, DOI: 10.1126/sciadv.abg3080

https://www.science.org/doi/10.1126/sciadv.abg3080

Abstract
Speedup of Pine Island Glacier over the past several decades has made it Antarctica’s largest contributor to sea-level rise. The past speedup is largely due to grounding-line retreat in response to ocean-induced thinning that reduced ice-shelf buttressing. While speeds remained fairly steady from 2009 to late 2017, our Copernicus Sentinel 1A/B–derived velocity data show a >12% speedup over the past 3 years, coincident with a 19-km retreat of the ice shelf. We use an ice-flow model to simulate this loss, finding that accelerated calving can explain the recent speedup, independent of the grounding-line, melt-driven processes responsible for past speedups. If the ice shelf’s rapid retreat continues, it could further destabilize the glacier far sooner than would be expected due to surface- or ocean-melting processes.

See also:

Title: "In ten years, this ice sheet could collapse, causing sea levels to rise"

https://www.weforum.org/agenda/2021/06/ice-shelf-pine-island-glacier-collapse/

Extract: ""The recent changes in speed are not due to melt-driven thinning; instead they're due to the loss of the outer part of the ice shelf," study lead author and UW glaciologist Ian Joughin said in the press release.

All of this means that the shelf and the glacier could both collapse much sooner than previously anticipated.

"It's not at all inconceivable to say the rest of the ice shelf could be gone in a decade," Joughin told The Washington Post. "It's a long shot. But it's not that big a long shot.""
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #152 on: September 29, 2021, 05:42:13 PM »
As we have previously concluded that AR6 recommendations are guided by politics; here I note that other SLR guidance authorities such as the State of California better recognize right-tail risks for SLR (see the H++ scenario values in the attached image) and discussed in the linked 2018 document.  Here I note that rapid SLR projections such as that indicated by the H++ scenario would also impact the Global Meridional Overturning Circulation (GMOC); which in turn would increase the effective ECS values in coming decades.

Title: "State of California Sea-Level Rise Guidance 2018 UPDATE"

http://www.opc.ca.gov/webmaster/ftp/pdf/agenda_items/20180314/Item3_Exhibit-A_OPC_SLR_Guidance-rd3.pdf

Extract: "Before 2050, differences in sea-level rise projections under different emissions scenarios are minor but they diverge significantly past mid-century. After 2050, sea-level rise projections increasingly depend on the trajectory of greenhouse gas emissions. For example, under the extreme H++ scenario rapid ice sheet loss on Antarctica could drive rates of sea-level rise in California above 50 mm/year (2 inches/year) by the end of the century, leading to potential sea-level rise exceeding 10 feet. This rate of sea-level rise would be about 30-40 times faster than the sea-level rise experienced over the last century."

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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #153 on: September 30, 2021, 12:08:13 AM »
Edwards et al. (2021), and the associated linked article (see the attached image that shows SLR values beyond those cited in AR6 & click the image to enlarge), indicate that for risk-averse individuals the Antarctic Ice Sheet represents a major climate change risk:

Edwards, T. L., Nowicki, S., Marzeion, B., Hock, R., Goelzer, H., Seroussi, H., et al. (2021). Projected land ice contributions to twenty-first-century sea level rise. Nature, 593(7857), 74–82. https://doi.org/10.1038/s41586-021-03302-y

https://www.nature.com/articles/s41586-021-03302-y

Abstract: "The land ice contribution to global mean sea level rise has not yet been predicted using ice sheet and glacier models for the latest set of socio-economic scenarios, nor using coordinated exploration of uncertainties arising from the various computer models involved. Two recent international projects generated a large suite of projections using multiple models, but primarily used previous-generation scenarios and climate models, and could not fully explore known uncertainties. Here we estimate probability distributions for these projections under the new scenarios using statistical emulation of the ice sheet and glacier models. We find that limiting global warming to 1.5 degrees Celsius would halve the land ice contribution to twenty-first-century sea level rise, relative to current emissions pledges. The median decreases from 25 to 13 centimetres sea level equivalent (SLE) by 2100, with glaciers responsible for half the sea level contribution. The projected Antarctic contribution does not show a clear response to the emissions scenario, owing to uncertainties in the competing processes of increasing ice loss and snowfall accumulation in a warming climate. However, under risk-averse (pessimistic) assumptions, Antarctic ice loss could be five times higher, increasing the median land ice contribution to 42 centimetres SLE under current policies and pledges, with the 95th percentile projection exceeding half a metre even under 1.5 degrees Celsius warming. This would severely limit the possibility of mitigating future coastal flooding. Given this large range (between 13 centimetres SLE using the main projections under 1.5 degrees Celsius warming and 42 centimetres SLE using risk-averse projections under current pledges), adaptation planning for twenty-first-century sea level rise must account for a factor-of-three uncertainty in the land ice contribution until climate policies and the Antarctic response are further constrained."

See also:

Title: "PROJECTED LAND ICE CONTRIBUTIONS TO 21ST-CENTURY SEA LEVEL RISE"

https://e3sm.org/projected-land-ice-contributions-to-21st-century-sea-level-rise/

Extract: "The risk-averse storylines – based on the most sensitive ice sheet and climate models – produce the highest amounts of sea level rise for the given emissions scenarios and are shown by the set of pale time-series lines and the rightmost box-and-whisker plots in Figure 1.

Results from the study confirm that Antarctica remains a critical focus for reducing future uncertainty in sea level rise. The team’s high-end estimates for sea level rise from Antarctic land ice are more than twice as large as the ‘most likely’ estimate. This is largely due to substantial uncertainty in how strongly warm ocean waters will erode floating parts of the ice sheet from beneath."

Caption for the attached image: "Figure 1. Projected 2015-2100 land ice contribution to sea level, in centimeters (cm) of sea level equivalent (SLE), for a range of emissions scenarios. The various SSP1, 2, 3, and 5 scenarios refer to the Shared Socioeconomic Pathways while NDC stands for nationally determined contributions reflecting current climate pledges made under the Paris Agreement. (The aspirational Paris Agreement 1.5°C goal corresponds to the SSP1-19 scenario.) Solid lines and shaded regions show median and 5-95th percentile estimates, respectively. Pale solid lines denote 95th percentiles for risk-averse projections. Box-and-whiskers indicate 5, 25, 50, 75, 95th percentiles at 2100. (Figure edited after Edwards et al., 2021)"

Also, I note that version 2.0 of the Energy Exascale Earth System Model (E3SMv2) was formally frozen on September 13, 2021.  Thus, we can soon expect journal articles regarding project support and data from the v2 DECK and historical simulations.
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #154 on: September 30, 2021, 05:45:37 PM »
Cesana et al. (2021) finds that:

"Our findings suggest that making radiation schemes precipitation-aware (missing in most CMIP6 models) should strengthen their positive cloud feedback and further increase their already high mean climate sensitivity."

Thus, as the mean CMIP6 value for ECS is likely too low; it appears that AR6 was incorrect to constrain the CMIP6 climate sensitivities to match the observed modern record estimates.

Cesana, G.V., et al. (23 September 2021), "Snow reconciles observed and simulated phase partitioning and increases cloud feedback", Geophysical Research Letters, https://doi.org/10.1029/2021GL094876

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL094876

Abstract
The surprising increase of Earth's climate sensitivity in the most recent Coupled Model Intercomparison Project (CMIP) models has been largely attributed to extratropical cloud feedback, which is thought to be driven by greater supercooled water in present-day cloud phase partitioning (CPP). Here we report that accounting for precipitation in the Goddard Institute for Space Studies ModelE3 radiation scheme, neglected in more than 60% of CMIP6 and 90% of CMIP5 models, systematically changes its apparent CPP and substantially increases its cloud feedback, consistent with results using CMIP models. Including precipitation in the comparison with Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) measurements and in model radiation schemes is essential to faithfully constrain cloud amount and phase partitioning, and simulate cloud feedbacks. Our findings suggest that making radiation schemes precipitation-aware (missing in most CMIP6 models) should strengthen their positive cloud feedback and further increase their already high mean climate sensitivity.

Plain Language Summary
The surprising increase of Earth's climate sensitivity – a proxy for future global warming – in the most recent climate models (CMIP6) has been largely attributed to the response of extratropical low clouds to warming. This cloud-climate feedback is thought to be driven by greater supercooled water in present-day cloud phase partitioning. Here we report that accounting for precipitation in climate model radiation schemes –neglected in more than 60% of CMIP6 and 90% of CMIP5 models– profoundly changes their apparent cloud phase partitioning and substantially increases their cloud-climate feedbacks, which has not been reported before. Including precipitation in the comparison with observations and in model radiation schemes is essential to faithfully constrain cloud amount and phase partitioning and simulate cloud-climate feedbacks. Our novel findings suggest that making radiation schemes precipitation-aware, which is missing in most CMIP6 models, should strengthen their positive cloud feedback and further increase their already high mean climate sensitivity
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #155 on: September 30, 2021, 06:17:00 PM »
I note that most CMIP6 did not properly consider the impact of freshwater flux (from ice meltwater) on the Southern Ocean deep convection; however, the E3SMv1 model better evaluated this impact that virtually all other CMIP6 models and it projected a relatively high effective ECS value.  Now, Gjermundsen et al. (2021) found that CMIP6 models that did not project a marked slowdown of the Southern Ocean deep convection also projected delayed warming of the Southern Ocean surface temperature by centuries.  I conclude from these findings support James Hansen's projections that a marked slowdown of the SMOC (Southern Ocean Meridional Overturning Circulation) due to possible high freshwater flux from ice meltwater into the Southern Ocean in coming decades will result in relatively high values of effective ECS (compared to those values projected by AR6), once the freshwater flux dissipates (circa the mid-21st century).

Gjermundsen, A., Nummelin, A., Olivié, D. et al. Shutdown of Southern Ocean convection controls long-term greenhouse gas-induced warming. Nat. Geosci. 14, 724–731 (2021). https://doi.org/10.1038/s41561-021-00825-x

https://www.nature.com/articles/s41561-021-00825-x

Abstract: "The effective climate sensitivity estimates the equilibrium response of near-surface temperature to doubling atmospheric carbon dioxide concentration and is a widely used metric to characterize potential global warming. Earth system models participating in phase 6 of the Coupled Model Intercomparison Project (CMIP6) exhibit considerable spread in effective climate sensitivity estimates. Cloud feedbacks are thought to be the cause of this, with marine boundary layer clouds over the Southern Ocean playing an important role. Here, we show that Southern Ocean deep convection is a major contributor to the CMIP6 intermodel spread in effective climate sensitivity. By comparing two Earth system models with very different sensitivities, we find that greater storage of heat at depth can delay the Southern Ocean surface warming and associated cloud response, thereby delaying global surface warming by centuries. The link between Southern Ocean convection and effective climate sensitivity is seen across 41 CMIP6 models, with low-sensitivity models exhibiting substantial deep ocean warming. Our results reveal the influence of Southern Ocean convection on potential long-term climate warming."
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #156 on: September 30, 2021, 06:22:05 PM »
Zhang et al. (2021) identifies a positive feedback between sea-ice loss and lapse-rate feedback for Arctic amplification.  To me this suggests that if/when rapid Arctic sea-ice loss occurs in the coming decades that the effective ECS will increase faster than that projected by AR6.

Zhang, R., et al. (27 September 2021), "Understanding the cold season Arctic surface warming trend in recent decades", Geophysical Research Letters, https://doi.org/10.1029/2021GL094878

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2021GL094878

Abstract
Whether sea-ice loss or lapse-rate feedback dominates the Arctic amplification remains an open question. Analysis of datasets based upon observations reveals a 1.11 K per decade surface warming trend in the Arctic (70-90°N) during 1979-2020 cold season (October-February) that is five times higher than the corresponding global mean. Based on surface energy budget analysis, we show that the largest contribution (∼82%) to this cold season warming trend is attributed to changes in clear-sky downward longwave radiation. In contrast to that in Arctic summer and over tropics, a reduction in lower-tropospheric inversions plays a unique role in explaining the reduction of the downward longwave radiation associated with atmospheric nonuniform temperature and corresponding moisture changes. Our analyses also suggest that Arctic lower-tropospheric stability should be considered in conjunction with sea-ice decline during the preceding warm season to explain Arctic amplification.

Plain Language Summary
Observations and climate models have consistently shown a stronger surface warming in the Arctic than the global mean, a.k.a. Arctic amplification (AA), which has a strong asymmetry between the cold season and warm season. Previous studies suggested that key contributors to AA are the positive surface-albedo feedback and lapse-rate feedback. However, the lapse-rate feedback itself depends on temperature profiles and sea-ice loss. Whether sea-ice loss or lapse-rate feedback dominates AA remains an open question. Here, by analyzing the latest generation of observationally based reanalysis data (1979-2020), we present a unique role of lower-tropospheric temperature inversion changes in representing the contribution of vertically inhomogeneous atmospheric temperature and associated moisture changes to clear-sky downward longwave radiation during the cold season. This unique role is not found either in the tropics or during Arctic summertime. We further link the inversion during the cold season to sea-ice loss during the preceding warm season. These results reinforce previous findings not only that lapse-rate feedback and sea-ice loss play a key role in AA but also that lapse-rate feedback in the cold season is likely a consequence of sea-ice albedo feedback during the preceding warm season.
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jai mitchell

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Re: AR6 physical science basis of climate change.
« Reply #157 on: September 30, 2021, 09:19:34 PM »
That Zhan paper really makes sense to me.  We can see very clearly how historic northern hemisphere aerosol emissions cycles and recent arctic circle wildfire smoke has affected the surface temperatures.

The impact of aerosols on lapse rates is found within the models but it is not well defined.  The impact of aerosols on arctic lapse rates appear to be quite massive.
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #158 on: October 03, 2021, 10:03:42 PM »
As AR6 has constrained the CMIP6 projections to follow observed trends I think that it is instructive to consider the accuracy of CMIP hindcasts for both GMSTA and GMST.  Therefore, attached I provide Figure 9.8 from AR5 for which the top panel shows both GMSTA and GMST from 1870 to 2012 (the observed record at that time) as hindcast CMIP5 models as compared to observed global mean surface temperatures.  My point in presenting this image is that while CMIP5 did a fairly good job of hindcasting GMSTA (compared to the observed) CMIP5 had a much larger spread for hindcasting GMST (as indicated by the bars on the right edge of the plot).  To me this indicates that while recent ESMs do a reasonably good job of simulating increases in GMSTA due to anthropogenic GHG emissions; they do not yet (as a group) do a good job of simulating GMST; which, is a significant problem for projecting the future risks of a possible cascade of tipping points such as abrupt freshwater fluxes from ice meltwater into the ocean triggering an abrupt slowdown of the GMOC, as ice melt is dependent upon absolute local temperatures and not relative global temperatures (GMSTA).  This is yet another example of consensus climate science erring on the side of least drama with regard to the messages that they deliver to both the public and to decision makers.
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jai mitchell

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Re: AR6 physical science basis of climate change.
« Reply #159 on: October 04, 2021, 09:05:50 PM »
2018
https://www.science.org/doi/10.1126/sciadv.aas9593

Large regional shortwave forcing by anthropogenic methane informed by Jovian observations

Quote
Recently, it was recognized that widely used calculations of methane radiative forcing systematically underestimated its global value by 15% by omitting its shortwave effects. We show that shortwave forcing by methane can be accurately calculated despite considerable uncertainty and large gaps in its shortwave spectroscopy. We demonstrate that the forcing is insensitive, even when confronted with much more complete methane absorption spectra extending to violet light wavelengths derived from observations of methane-rich Jovian planets. We undertake the first spatially resolved global calculations of this forcing and find that it is dependent on bright surface features and clouds. Localized annual mean forcing from preindustrial to present-day methane increases approaches +0.25 W/m2, 10 times the global annualized shortwave forcing and 43% of the total direct CH4 forcing. Shortwave forcing by anthropogenic methane is sufficiently large and accurate to warrant its inclusion in historical analyses, projections, and mitigation strategies for climate change.



I note that this additional forcing from CH4 is coincident with the increased cloud radiative forcing  observed in the CERES data for the Eastern South Pacific.

It does not appear that this effect was adequately captured in the CMIP6 model runs.
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jai mitchell

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Re: AR6 physical science basis of climate change.
« Reply #160 on: October 04, 2021, 09:58:03 PM »
According to my sources:

The AR6 included the near-term infrared forcing from 
Etminan et al paper from

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL071930

 ;D
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #161 on: October 08, 2021, 09:20:33 PM »
The linked 2019 article on scientific reticence and climate change messaging (to both the public and to decision makers) is relevant to AR6, and it recommends that climate change scientists should follow the same code of moral ethics as other relevant professions such as engineers and medical practitioners, regarding climate risk.

Title: "Scientific reticence is a serious threat when it comes to climate change"

https://www.downtoearth.org.in/blog/climate-change/scientific-reticence-is-a-serious-threat-when-it-comes-to-climate-change-66204

Extract: “Challenges faced by scientists in finding the right balance between reticence and speaking out are both ethical and methodological,” according to a study published last year in the journal Ethics, Policy and Environment.

“Scientists need a framework within which to find this balance. Such a framework can be found in the long-established practices of professional ethics (for example, that followed by engineers and medical practitioners),” it added.

The study discusses plausible reasons (good and bad) for scientific reticence, ranging from a simple and understandable fear of being wrong because of uncertainty in predictions to other reasons like fear of losing funding and facing disapproval from colleagues and the community at large.

It goes on to propose that scientists may be subject to the same code of moral ethics — Duty to Report and Epistemic Privilege — as other professionals in fields such as engineering and medicine.

The Duty to Report says, “[they] must act out of a sense of duty, with full knowledge of the effect of their actions, and accept responsibility for their judgement [in a way that is] open, personal, [and] conducted with the interest of the public in mind.”

Epistemic Privilege means that professionals are presumed to have access to knowledge that is not available to other members of society. It is entirely appropriate, and indeed it may be required, for them to speak out — even if there is an appreciable chance that they are wrong."
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kassy

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Re: AR6 physical science basis of climate change.
« Reply #162 on: October 11, 2021, 05:56:23 PM »
What 100,000 studies tell us about climate impacts around the world

The rapid growth of climate research provides an unprecedented evidence base for observing the impacts of climate change across the globe.

However, the sheer volume of published studies means attempting to evaluate it as a whole makes for a daunting challenge.

In our new study, published in Nature Climate Change, we used machine-learning approaches to assess, classify and map more than 100,000 peer-reviewed studies on climate impacts.

Our findings show that the influence of human-caused warming on average temperature and rainfall can already be felt for 85% of the world’s population and 80% of the world’s area.

The results also highlight an “attribution gap” between countries in the global north and south, due to a relative lack of research on climate impacts in less-developed countries.

...

By itself, the first part of the IPCC’s most recent assessment report – published in August – references more than 14,000 scientific papers.

This exponential growth in peer-reviewed scientific publications on climate change is already pushing manual expert assessments to their limits.

In this study, we develop an approach using machine learning – developing an algorithm that can recognise not just whether a study is about climate impacts, but the locations mentioned, the climate impact driver – whether the impacts were caused by temperature or precipitation changes – and the type of impacts described.

To do so, we use the state-of-the-art deep-learning language representation model, called “BERT”. The model can capture context-dependent meanings of texts, which means it can extract the information we are looking for from each study we analysed.

We trained our algorithm using “supervised learning”, which involves our team hand-coding more than 2,000 documents. Our algorithm was then able to replicate the classification decisions made by humans well. The predictions it makes are, of course, not perfect, but our approach allows us to assess uncertainty ranges of our predictions explicitly.

From our experience with double-coded documents by different human coders, we can testify that human classification is not without errors or disagreement. How the performance of machine learning and human coders compare is an interesting area for further research.

https://www.carbonbrief.org/guest-post-what-100000-studies-tell-us-about-climate-impacts-around-the-world

See link for full details and the Interactive map showing weight of evidence of climate impacts by grid cell across the globe and the attribution map and graphic.

 
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Re: AR6 physical science basis of climate change.
« Reply #163 on: October 12, 2021, 05:03:20 PM »
When Global Warming Stops, Seas Will Still Rise: Study
https://phys.org/news/2021-10-global-seas.html

In a world that heats up another half-degree above that benchmark, an additional 200 million of today's urban dwellers would regularly find themselves knee-deep in sea water and more vulnerable to devastating storm surges, they reported in Environmental Research Letters.

"Roughly five percent of the world's population today live on land below where the high tide level is expected to rise based on carbon dioxide that human activity has already added to the atmosphere," lead author Ben Strauss, CEO and chief scientist of Climate Central, told AFP.



The 1.5C warming limit enshrined in the Paris Agreement that nations will try to keep in play at the COP26 climate summit in Glasgow next month translates into nearly three meters over the long haul.

Unless engineers figure out how to quickly remove massive amounts of CO2 from the atmosphere, that amount of sea level rise is not a matter of "if" but "when", according to the study.

These are the optimistic scenarios.

"The headline finding for me is the stark difference between a 1.5C world after sharp pollution cuts versus a world after 3C or 4C of warming," Strauss said.

"At Glasgow and for the rest of this decade, we have the chance to help or to betray a hundred generations to come."

... At higher levels of warming, the danger increases substantially of triggering the irreversible disintegration of ice sheets or the release of natural stores of CO2 and methane in permafrost, scientists warn.

Benjamin H Strauss et al, Unprecedented threats to cities from multi-century sea level rise, Environmental Research Letters (2021)
https://iopscience.iop.org/article/10.1088/1748-9326/ac2e6b
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Re: AR6 physical science basis of climate change.
« Reply #164 on: October 12, 2021, 11:31:40 PM »
The linked reference, and associated linked article, indicate that that less than half of the sulfur marine plankton released as dimethyl sulfide (DMS) can help nucleate clouds.  As consensus climate change model currently do not account for this reduced rate of cloud formation (and possible reduction in net cloud brightness); this is yet another example of where consensus climate change science (including AR6) has erred on the side of least drama.

Gordon A. Novak, G.A., et al. (11 October 2021), “Rapid cloud removal of dimethyl sulfide oxidation products limits SO and cloud condensation nuclei production in the marine atmosphere”, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2110472118

https://www.pnas.org/content/118/42/e2110472118

Significance
Ocean emissions of dimethyl sulfide (DMS) are a major precursor for the production and growth of aerosol particles, which can act as seeds for the formation of cloud droplets in the marine atmosphere with the subsequent impacts on Earth’s climate. Global aircraft observations indicate that DMS is efficiently oxidized to hydroperoxymethyl thioformate (HPMTF), a previously unrecognized molecule, which necessitates revisiting DMS oxidation chemistry in the marine atmosphere. We show through ambient observations and global modeling that a dominant loss pathway for HPMTF is uptake into cloud droplets. This loss process short circuits gas-phase oxidation and significantly alters the dynamics of aerosol production and growth in the marine atmosphere.

Abstract
Oceans emit large quantities of dimethyl sulfide (DMS) to the marine atmosphere. The oxidation of DMS leads to the formation and growth of cloud condensation nuclei (CCN) with consequent effects on Earth’s radiation balance and climate. The quantitative assessment of the impact of DMS emissions on CCN concentrations necessitates a detailed description of the oxidation of DMS in the presence of existing aerosol particles and clouds. In the unpolluted marine atmosphere, DMS is efficiently oxidized to hydroperoxymethyl thioformate (HPMTF), a stable intermediate in the chemical trajectory toward sulfur dioxide (SO2) and ultimately sulfate aerosol. Using direct airborne flux measurements, we demonstrate that the irreversible loss of HPMTF to clouds in the marine boundary layer determines the HPMTF lifetime (τHPMTF < 2 h) and terminates DMS oxidation to SO2. When accounting for HPMTF cloud loss in a global chemical transport model, we show that SO2 production from DMS is reduced by 35% globally and near-surface (0 to 3 km) SO2 concentrations over the ocean are lowered by 24%. This large, previously unconsidered loss process for volatile sulfur accelerates the timescale for the conversion of DMS to sulfate while limiting new particle formation in the marine atmosphere and changing the dynamics of aerosol growth. This loss process potentially reduces the spatial scale over which DMS emissions contribute to aerosol production and growth and weakens the link between DMS emission and marine CCN production with subsequent implications for cloud formation, radiative forcing, and climate.

See also:

Title: " Massive Flying Laboratory Uncovers Secrets of How Marine Life Influences Cloud Formation"

https://scitechdaily.com/massive-flying-laboratory-uncovers-secrets-of-how-marine-life-influences-cloud-formation/

Extract: "From the flight data, the team discovered that HPMTF readily dissolves into the water droplets of existing clouds, which permanently removes that sulfur from the cloud nucleation process. In cloud-free areas, more HPMTF survives to become sulfuric acid and help form new clouds.

Led by collaborators from Florida State University, the team accounted for these new measurements in a large, global model of ocean atmospheric chemistry. They discovered that 36% of the sulfur from DMS is lost to clouds in this way. Another 15% of sulfur is lost through other processes, so the upshot is that less than half of the sulfur marine plankton release as DMS can help nucleate clouds.

“This loss of sulfur to the clouds reduces the formation rate of small particles, so it reduces the formation rate of the cloud nuclei themselves. The impact on cloud brightness and other properties will have to be explored in the future,” says Bertram.
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #165 on: October 14, 2021, 04:49:09 PM »
The linked Wikipedia article discusses both physical reasons why abrupt climate change may occur in the near future as well as indicating that by one definition abrupt climate change occurs so rapidly that human, or natural, systems cannot effective adapt to avoid major impacts.  Also, the article indicates that current climate models (e.g. CMIP6 and AR6) are unable to predict any such potential up-coming abrupt climate change in the near future.

Title: "Abrupt climate change"

https://en.wikipedia.org/wiki/Abrupt_climate_change

Extract: "According to the Committee on Abrupt Climate Change of the National Research Council:

There are essentially two definitions of abrupt climate change:

•   In terms of physics, it is a transition of the climate system into a different mode on a time scale that is faster than the responsible forcing.
•   In terms of impacts, "an abrupt change is one that takes place so rapidly and unexpectedly that human or natural systems have difficulty adapting to it".

Climate models are currently unable to predict abrupt climate change events, or most of the past abrupt climate shifts.

Most abrupt climate shifts are likely due to sudden circulation shifts, analogous to a flood cutting a new river channel. The best-known examples are the several dozen shutdowns of the North Atlantic Ocean's Meridional Overturning Circulation during the last ice age, affecting climate worldwide.

•   The current warming of the Arctic, the duration of the summer season, is considered abrupt and massive.
•   Antarctic ozone depletion caused significant atmospheric circulation changes.
•   There have also been two occasions when the Atlantic's Meridional Overturning Circulation lost a crucial safety factor. The Greenland Sea flushing at 75 °N shut down in 1978, recovering over the next decade. Then the second-largest flushing site, the Labrador Sea, shut down in 1997 for ten years. While shutdowns overlapping in time have not been seen during the 50 years of observation, previous total shutdowns had severe worldwide climate consequences."
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Alumril

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Re: AR6 physical science basis of climate change.
« Reply #166 on: October 18, 2021, 03:17:44 AM »
Apologies if this is old news, but I just came across University of Melbourne's CMIP6 data viewer.
https://cmip6.science.unimelb.edu.au/
I'm not sure if it's just me or if they are missing data sets from some of the models, but it's quite fun to see what each of the models actually predicts for each of the scenarios. And you can compare for specific sections of the planet.
Their Climate & Energy College has an interesting YouTube channel:
https://www.youtube.com/channel/UCW5p91a9x0PCmwkYcIX4PbA/featured
Including this video which discusses the CMIP6 data viewer:


jai mitchell

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Re: AR6 physical science basis of climate change.
« Reply #167 on: October 18, 2021, 09:04:42 PM »
Apologies if this is old news, but I just came across University of Melbourne's CMIP6 data viewer.
https://cmip6.science.unimelb.edu.au/
I'm not sure if it's just me or if they are missing data sets from some of the models, but it's quite fun to see what each of the models actually predicts for each of the scenarios. And you can compare for specific sections of the planet.
Their Climate & Energy College has an interesting YouTube channel:
https://www.youtube.com/channel/UCW5p91a9x0PCmwkYcIX4PbA/featured
Including this video which discusses the CMIP6 data viewer:


That was captivating!  Thank you for sharing!
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Tor Bejnar

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Re: AR6 physical science basis of climate change.
« Reply #168 on: October 18, 2021, 09:59:54 PM »
Hope this is a good place to drop this ...
https://www.realclimate.org/index.php/archives/2021/10/a-nobel-pursuit/ (posted Oct. 12, 2021)
Quote
Last week, the Nobel physics prize was (half) awarded to Suki Manabe and Klaus Hasselmann for their work on climate prediction and the detection and attribution of climate change. This came as quite a surprise to the climate community – though it was welcomed warmly. We’ve discussed the early climate model predictions a lot (including some from Manabe and his colleagues), and we’ve discussed detection and attribution of climate change as well, though with less explicit discussion of Hasselmann’s contribution. Needless to say these are big topics which have had many inputs from many scientists over the years.

But RC has a more attuned audience to these topics than most, and so it might be fun to dive into the details of their early work to see what has stood the test of time and what has not, and how that differs (if it does) from their colleagues and rivals at the time.
...
Arctic ice is healthy for children and other living things because "we cannot negotiate with the melting point of ice"

vox_mundi

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Re: AR6 physical science basis of climate change.
« Reply #169 on: October 22, 2021, 01:08:36 PM »
Climate Tipping Might Be Predicted Using Algebraic Topology
https://phys.org/news/2021-10-climate-algebraic-topology.html

... Analyzing a model that combines the two leading theories for climate change with algebraic topology tools, researchers show that the climate system indeed progresses through abrupt transitions, also known as tipping points. These tools are applicable to reduced climate models and they well might help assess whether the Earth's climate system on a whole is about to tip due to global warming. The work is part of the TiPES project, a European science collaboration on tipping points in the Earth system.

... There have been essentially two complementary views of what makes climate evolve. One is the deterministically chaotic view of Edward Lorenz. This is the chaos theory that is widely known through the idea that a butterfly flapping its wings on one continent can be the origin of a raging storm on another continent.

The other view is that of Klaus Hasselmann, the recent Nobel Prize winner, who said the climate system is stochastic and everything fluctuates but regresses to the mean.

"We have earlier, in 2008, brought these two theories together and shown that things get a lot more interesting if you have both deterministic chaos and stochastic perturbations," says Michael Ghil.

The result from 2008, a so-called random attractor, changes with time. The shape it takes at a given instant, called a snapshot, determines where the climate system is most likely to be. It has not been clear, however, how to interpret the random attractor's changes in time. What does its changing path mean for our understanding of the climate? Algebraic topology now helps with that.

The analysis in Chaos of the climate's random attractor reveals that over time, holes appear and disappear. This means the system shifts between different regimes. The transitions seem to be instantaneous. And because the analysis in effect reveals changes in the most fundamental properties of the physical system being analyzed, the results suggest that the nature of Earth's climate indeed is to evolve through abrupt transitions—commonly known as tipping points.

Gisela D. Charó et al, Noise-driven topological changes in chaotic dynamics, Chaos: An Interdisciplinary Journal of Nonlinear Science (2021)
https://aip.scitation.org/doi/10.1063/5.0059461
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #170 on: October 24, 2021, 11:57:52 PM »
Bonnet et al. (2021) studied the increased risk of near-term global warming due to recent AMOC weakening and they found that AR6 may likely have acted too hastily when they artificially constrained the CMIP6 model projections that indicated relatively high climate sensitivities (both high ECS and high TCR) to better match AR6's interpretation of the historical record over the past 6 to 7 decades.  Specifically, this reference concludes that:

"To conclude, we have shown here that the different indications of an AMOC weakening since the mid-20th century might be mainly of internal origin coming from multi-centennial variability of the ocean. If true, this might mean that transient climate sensitivity estimated from the observational records, especially over the last 6–7 decades may be underestimated. Thus, emergent constraint approaches that try to constrain future warming using the recent decades should fully embrace the issue of low-frequency internal variability and take into account individual ensemble members rather than ensemble means, as this might have crucial implications in terms of how different models are weighted in such studies."

These findings supports the idea that the ranges of climate sensitivities presented by AR6 err on the side of least drama because AR6 does not correctly account for the issue of low-frequency internal variability of the AMOC in their estimates of climate sensitivity.

Bonnet, R., Swingedouw, D., Gastineau, G. et al. Increased risk of near term global warming due to a recent AMOC weakening. Nat Commun 12, 6108 (2021). https://doi.org/10.1038/s41467-021-26370-0

https://www.nature.com/articles/s41467-021-26370-0

Abstract: "Some of the new generation CMIP6 models are characterised by a strong temperature increase in response to increasing greenhouse gases concentration. At first glance, these models seem less consistent with the temperature warming observed over the last decades. Here, we investigate this issue through the prism of low-frequency internal variability by comparing with observations an ensemble of 32 historical simulations performed with the IPSL-CM6A-LR model, characterized by a rather large climate sensitivity. We show that members with the smallest rates of global warming over the past 6-7 decades are also those with a large internally-driven weakening of the Atlantic Meridional Overturning Circulation (AMOC). This subset of members also matches several AMOC observational fingerprints, which are in line with such a weakening. This suggests that internal variability from the Atlantic Ocean may have dampened the magnitude of global warming over the historical era. Taking into account this AMOC weakening over the past decades means that it will be harder to avoid crossing the 2 °C warming threshold."

Extract: "Implications for future global warming and discussion. Our analysis suggests that a fraction of anthropogenic warming might have been hidden by an AMOC weakening that started in the middle of the 20th century and is mainly related to internal climate variability. Indeed, the subset of members identified previously, which is characterized by a strong AMOC weakening over the 1951–1990 period in comparison to the IPSL-EHS (Fig. 5a, b) shows a lower warming over the same period relative to the full IPSL-EHS (Fig. 5c, d).

To conclude, we have shown here that the different indications of an AMOC weakening since the mid-20th century might be mainly of internal origin coming from multi-centennial variability of the ocean. If true, this might mean that transient climate sensitivity estimated from the observational records, especially over the last 6–7 decades may be underestimated. Thus, emergent constraint approaches that try to constrain future warming using the recent decades should fully embrace the issue of low-frequency internal variability and take into account individual ensemble members rather than ensemble means, as this might have crucial implications in terms of how different models are weighted in such studies."
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jai mitchell

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Re: AR6 physical science basis of climate change.
« Reply #171 on: October 25, 2021, 10:42:02 PM »
I have long posited a hypothesis that a significant portion of the longer-term LIA (after the eruption of Samalas in 1257 AD) was caused by Mayan culture forest clearing of the Amazon.  Leading to a slowing of the AMOC.
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AbruptSLR

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Re: AR6 physical science basis of climate change.
« Reply #172 on: November 04, 2021, 07:20:43 PM »
Shepherd (2021) examines three examples of climate change data interpretation to illustrate the value of bringing physical reasoning into statistical practice in climate change science.  To me, the cited methodology brings into focus the value of the physical ice-climate narrative outlined in the MCDS threads to help identify true climate change risks of abrupt climate change in the coming decades.

Shepherd, T.G. Bringing physical reasoning into statistical practice in climate-change science. Climatic Change 169, 2 (2021). https://doi.org/10.1007/s10584-021-03226-6

https://link.springer.com/article/10.1007%2Fs10584-021-03226-6

Abstract: "The treatment of uncertainty in climate-change science is dominated by the far-reaching influence of the ‘frequentist’ tradition in statistics, which interprets uncertainty in terms of sampling statistics and emphasizes p-values and statistical significance. This is the normative standard in the journals where most climate-change science is published. Yet a sampling distribution is not always meaningful (there is only one planet Earth). Moreover, scientific statements about climate change are hypotheses, and the frequentist tradition has no way of expressing the uncertainty of a hypothesis. As a result, in climate-change science, there is generally a disconnect between physical reasoning and statistical practice. This paper explores how the frequentist statistical methods used in climate-change science can be embedded within the more general framework of probability theory, which is based on very simple logical principles. In this way, the physical reasoning represented in scientific hypotheses, which underpins climate-change science, can be brought into statistical practice in a transparent and logically rigorous way. The principles are illustrated through three examples of controversial scientific topics: the alleged global warming hiatus, Arctic-midlatitude linkages, and extreme event attribution. These examples show how the principles can be applied, in order to develop better scientific practice.

“La théorie des probabilités n’est que le bon sens reduit au calcul.” (Pierre-Simon Laplace, Essai Philosophiques sur les Probabilités, 1819).

“It is sometimes considered a paradox that the answer depends not only on the observations but on the question; it should be a platitude.” (Harold Jeffreys, Theory of Probability, 1st edition, 1939)."

Extract: "For climate information to be useable, its uncertainties must be comprehensible and salient, especially in the face of apparently conflicting sources of information, and the connection between statistical analysis and physical reasoning must be explicit rather than implicit. This argues for bringing the Bayesian spirit of hypothesis testing more explicitly into our scientific reasoning, forgoing the ‘mindless’ performance of statistical rituals as a substitute for reasoning, resisting true/false dichotomization, and being ever vigilant for logical errors such as multiple testing and the transposed conditional. As a recent Nature editorial states (Anonymous 2019), “Looking beyond a much used and abused measure [statistical significance] would make science harder, but better.” Yet we can still use familiar statistical tools, such as p-values and confidence intervals, so long as we remember what they do and do not mean. They are useful heuristics, which researchers have some experience interpreting. And we need to make sure that we are not chasing phantoms.

Neuroscience has shown that human decision-making cannot proceed from facts alone but involves an emotional element, which provides a narrative within which the facts obtain meaning (Damasio 1994). Narratives are causal accounts, which in the scientific context can be regarded as hypotheses. To connect physical reasoning and statistical practice, these narratives need to run through the entire scientific analysis, not simply be a ‘translation’ device bolted on at the end. To return to the quote from Jeffreys at the beginning of this piece, we need to recognize that data does not speak on its own; there is no answer without a question, and the answer depends not only on the question but also on how it is posed."
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kassy

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Re: AR6 physical science basis of climate change.
« Reply #173 on: February 28, 2022, 04:56:29 PM »
The working group II report is out. For the general outline i recycled a post by vox:

UN Climate Report: 'Atlas of Human Suffering' Worse, Bigger
https://phys.org/news/2022-02-climate-atlas-human-worse-bigger.html



Deadly with extreme weather now, climate change is about to get so much worse. It is likely going to make the world sicker, hungrier, poorer, gloomier and way more dangerous in the next 18 years with an "unavoidable" increase in risks, a new United Nations science report says.

And after that watch out.


Report: https://www.ipcc.ch/report/ar6/wg2/

The UN Intergovernmental Panel on Climate Change report said Monday if human-caused global warming isn't limited to just another couple tenths of a degree, an Earth now struck regularly by deadly heat, fires, floods and drought in future decades will degrade in 127 ways with some being "potentially irreversible."

"The cumulative scientific evidence is unequivocal: Climate change is a threat to human well-being and planetary health," says the major report designed to guide world leaders in their efforts to curb climate change. Delaying cuts in heat-trapping carbon emissions and waiting on adapting to warming's impacts, it warns, "will miss a brief and rapidly closing window of opportunity to secure a liveable and sustainable future for all."

Today's children who may still be alive in the year 2100 are going to experience four times more climate extremes than they do now even with only a few more tenths of a degree of warming over today's heat. But if temperatures increase nearly 2 more degrees Celsius from now (3.4 degrees Fahrenheit) they would feel five times the floods, storms, drought and heat waves, according to the collection of scientists at the IPCC.

More people are going to die each year from heat waves, diseases, extreme weather, air pollution and starvation because of global warming, the report says. Just how many people die depends on how much heat-trapping gas from the burning of coal, oil and natural gas gets spewed into the air and how the world adapts to an ever-hotter world, scientists say.

Since the last version of this impacts panel's report in 2014, "all the risks are coming at us faster than we thought before," said report co-author Maarten van Aalst, a climate scientist for the International Federation of Red Cross and Red Crescent Societies, mentioning floods, droughts and storms. "More of it will get really bad much sooner than we thought before."

If warming exceeds a few more tenths of a degree, it could lead to some areas becoming uninhabitable, including some small islands, said report co-author Adelle Thomas of the University of Bahamas and Climate Analytics.

And eventually in some places it will become too hot for people to work outdoor, which will be a problem for raising crops, said report co-author Rachel Bezner Kerr of Cornell University.

If the world warms just another nine-tenths of a degree Celsius from now (1.6 degrees Fahrenheit), the amount of land burned by wildfires globally will increase by 35%, the report says.



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

Climate Change: IPCC Report Warns of ‘Irreversible’ Impacts of Global Warming
https://www.bbc.com/news/science-environment-60525591

The contrast between the two reports is rather stark in tone.
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vox_mundi

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Re: AR6 physical science basis of climate change.
« Reply #174 on: April 04, 2022, 12:26:17 AM »
No Longer a Last Resort: Must Pull CO2 from the Air - Or No Tomorrow
https://phys.org/news/2022-04-longer-resort-co2-air.html

To save the world from the worst ravages of climate change, slashing carbon pollution is no longer enough—CO2 will also need to be sucked out of the atmosphere and buried, a landmark UN report is expected to say on Monday.

If humanity had started to curb greenhouse gas emissions 20 years ago, an annual decrease of two percent out to 2030 would have put us on the right path. Challenging, but doable.

Instead, the emissions climbed another 20 percent to more than 40 billion tonnes of CO2 in 2021.

This means an abrupt drop in emissions of 6 or 7% a year (for the next 30 years) is needed to avoid breaching the Paris climate treaty's goal of capping global warming at "well below" two degrees Celsius compared to pre-industrial levels.

Staying under the safer aspirational threshold of 1.5C would mean an even steeper decline.


To put that in perspective, the painful 2020 shutdown of the global economy due to COVID saw "only" a 5.6% decrease in CO2 emissions.

Hence the need for carbon dioxide removal (CDR), or "negative emissions", likely to figure prominently in the UN Intergovernmental Panel on Climate Change (IPCC) report.

Even under the most aggressive carbon-cutting scenarios, several billion tonnes of CO2 will need to be extracted each year from the atmosphere by 2050, and an accumulated total of hundreds of billions of tonnes by 2100.

As of today, however, CO2 removal is nowhere near these levels. The largest direct air capture facility in the world removes in a year what humanity emits in 3 or 4 seconds.
“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

kassy

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Re: AR6 physical science basis of climate change.
« Reply #175 on: April 04, 2022, 09:57:15 PM »
If humanity had started to curb greenhouse gas emissions 20 years ago, an annual decrease of two percent out to 2030 would have put us on the right path. Challenging, but doable.

It is also 40 years or so since we shifted from 1C and about 70 years from the still quite accurate 1950 predictions from the oil companies....

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jai mitchell

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Re: AR6 physical science basis of climate change.
« Reply #176 on: April 06, 2022, 12:33:33 AM »
I made this graphic from the Arora et al 2020 paper cited in the AR6 that looks at carbon soil loss under warming with the comprehensive work from Crowther et al 2016 looking at soil carbon studies using fieldwork analysis.  This is the result.
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vox_mundi

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Re: AR6 physical science basis of climate change.
« Reply #177 on: May 26, 2022, 08:48:10 PM »
New Data Reveals Climate Change Might Be More Rapid Than Predicted
https://phys.org/news/2022-05-reveals-climate-rapid.html

A new study, published today in Nature Climate Change, will certainly make the IPCC—and other environmental bodies—take notice. A team of scientists led by Dr. Rei Chemke of Weizmann's Earth and Planetary Sciences Department revealed a considerable intensification of winter storms in the Southern Hemisphere. Until now, climate models have projected a human-caused intensification of winter storms only toward the end of this century.

In the new study, Chemke and his team compared climate model simulations with current storm observations. Their discovery was bleak: It became clear that storm intensification over recent decades has already reached levels projected to occur in the year 2080.




"A winter storm is a weather phenomenon that lasts only a few days. Individually, each storm doesn't carry much climatic weight. However, the long-term effect of winter storms becomes evident when assessing cumulative data collected over long periods of time," Chemke explains. Cumulatively, these storms have a significant impact, affecting the transfer of heat, moisture and momentum within the atmosphere, which consequently affects the various climate zones on Earth."One example of this is the role the storms play in regulating the temperature at the Earth's poles. Winter storms are responsible for the majority of the heat transport away from tropical regions toward the poles. Without their contribution, the average pole temperatures would be about 30°C lower." Similarly, the collective intensification of these storms yields a real and significant threat to societies in the Southern Hemisphere in the next decades.

"We chose to focus on the Southern Hemisphere because the intensification registered there has been stronger than in the Northern Hemisphere," Chemke says. "We didn't examine the Northern Hemisphere, but it seems that the intensification of storms in this hemisphere is slower compared to that in the Southern Hemisphere. If the trend persists," Chemke adds, "we will be observing more significant winter storm intensification here in the upcoming years and decades."

In his lab at the Weizmann Institute, Chemke researches the physical mechanisms underlying large-scale climate change. In this study, he and his research partners sought to understand whether these changes in climate patterns were caused by external factors (such as human activity), or whether they have resulted from the internal fluctuations of the global climate system. They analyzed climate models that simulated storm intensification patterns under the isolated influence of internal climatic causes, without external impact. They showed that over the past 20 years, storms have been intensifying faster than can be explained by internal climatic behavior alone.

In addition, the researchers discovered the physical process behind the storm intensification. An analysis of the growth rate of the storms showed that changes in atmospheric jet streams over the past few decades have caused these escalations, and current climate models are unable to reflect these changes accurately.

Chemke, Ming and Yuval's study has two immediate, considerable implications. First, it shows that not only climate projections for the coming decades are graver than previous assessments, but it also suggests that human activity might have a greater impact on the Southern Hemisphere than previously estimated. This means that rapid and decisive intervention is required in order to halt the climate damage in this region. Second, a correction of the bias in climate models is in order, so that these can provide a more accurate climate projection in the future.



... Climate scientists will now be able to estimate more accurately the extent of the damage that climate change is expected to wreak—damage that will only be mitigated if humanity intervenes and takes responsibility for the future of the planet.

Rei Chemke, The intensification of winter mid-latitude storm tracks in the Southern Hemisphere, Nature Climate Change (2022).
https://www.nature.com/articles/s41558-022-01368-8

... the fat lady's singing ...
« Last Edit: May 26, 2022, 09:24:24 PM by vox_mundi »
“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

kassy

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Re: AR6 physical science basis of climate change.
« Reply #178 on: May 27, 2022, 07:59:03 PM »
This summer was pretty brutal in the southern hemisphere. They have much more water which means that the effects are different. Much worse winter storms fit with that. And that is probably not good for Antarctic ice. Really curious about the actual 2030 SLR data but we will see..
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kassy

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Re: AR6 physical science basis of climate change.
« Reply #179 on: March 21, 2023, 05:49:13 PM »
UN climate report: Scientists release 'survival guide' to avert climate disaster


UN chief Antonio Guterres says a major new report on climate change is a "survival guide for humanity".

Clean energy and technology can be exploited to avoid the growing climate disaster, the report says.

But at a meeting in Switzerland to agree their findings, climate scientists warned a key global temperature goal will likely be missed.

Their report lays out how rapid cuts to fossil fuels can avert the worst effects of climate change.

In response to the findings, UN secretary general Antonio Guterres says that all countries should bring forward their net zero plans by a decade. These targets are supposed to rapidly cut the greenhouse gas emissions that warm our planet's atmosphere.

"There is a rapidly closing window of opportunity to secure a liveable and sustainable future for all," the report states.

Governments had previously agreed to act to avoid global temperature rise going above 1.5C. But the world has already warmed by 1.1C and now experts say that it is likely to breach 1.5C in the 2030s.

...

"Leaders of developed countries must commit to reaching net zero as close as possible to 2040, the limit they should all aim to respect," he said in a statement. He also calls on the likes of India and China who have announced net zero plans for beyond 2050 to try and bring them forward by a decade as well.

https://www.bbc.com/news/science-environment-65000182

All the usual but at least the focus is now solidly on the near term future.

This is of course a bit too late but at least we get to see what 1.5C does so we can check if it was a really bad idea to make that the target...

We might test it before the 2030s but we will see.

So this is part 3 of AR6 which is mainly about solutions.

Then there was this article where two scientists expressed surprise at how big the difference between 1,5 and 2,0 C was so maybe there is more on that in the report too but i haven´t checked.

Of course basic physics sort of tells you that.

Report:
https://www.ipcc.ch/report/sixth-assessment-report-cycle/
« Last Edit: March 21, 2023, 06:20:13 PM by kassy »
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