Hi Mike et al., I can't get involved in a back-and-forth -- we are in the process of moving back to NYC, to live in a Columbia apartment to avoid time wasted in commuting and taking care of a house/property. However, I'm surprised by your comment, Mike. Most GCM groups make hundreds, if not more, GCM runs between one IPCC report and the next, and there are hundreds, if not more, model parameters. There is a widespread, if not universal, tendency to prefer those model configurations that yield a magnitude of warming in the past 200 years that is consistent with observations. In this way, wittingly or not, the 3C sensitivity is "baked into" the models -- because, as we showed in our "Acceleration" the usual aerosol forcing employed is close to the IPCC best estimate for aerosol forcing. As shown by a graph in the Supplementary Information of our paper, the change of the IPCC aerosol forcing during the period of rapid warming is negligible. In such case, the climate sensitivity required to match the observed warming rate is ~3C for 2xCO2. However, if the aerosol forcing increased by ~0.5 W/m2 (became more negative) during 1970-2005, as simulated by Bauer et al. and as independently inferred in our paper, then a climate sensitivity of ~4.5C is required to match the observed warming.
However, the temperature change in the last 200 years is only one of the three independent ways that we obtain the 4.5C sensitivity, and the other two are much cleaner, independent of the GCM issues. High climate sensitivity demanded by large cloud feedback, clearly shown by Earth's darkening in the past 25 years, is summarized in the recent communication to my email list. The third method is described in our "Global warming in the pipeline" paper: comparison of equilibrium glacial and interglacial climates. For several decades, based largely on CLIMAP and "confirmed" by MARGO, it was believed that the LGM was only 3-4C colder than the Holocene. Thanks especially to Alan Seltzer, we now know that the LGM was 6-7C colder, which demands the higher ECS -- several new paleo studies confirm the high ECS. Best, Jim On Mon, May 19, 2025 at 3:39 PM 'Michael MacCracken' via geoengineering < [email protected]> wrote: > Ron et al.--Just a note that the 3 C sensitivity is not "embedded" in the > climate models. That is the value that emerges from the representations of > the various physical processes that play out against each other. So, > assuming the observations and resulting analyses are accurate, for there to > be a higher sensitivity, it might be that some of the processes are not > parameterized in a way that fully represents possibilities and realities > (observations to calibrate parameterizations can be drawn from only the > conditions we are experiencing), some processes are not represented at > all (viewed as long-term such as isostatic rebound, etc.), the resolution > of the models is not fine enough to treat aspects of the processes, etc. In > any case, however, the 3 C sensitivity is not built into the models. > > Mike > On 5/19/25 1:49 PM, Ron Baiman wrote: > > Thank you LDM and Dan, > > @LDM: > > (IMO) Thanks for sharing! IMO this recent Hansen and Kharecha Newsletter > with further evidence supporting a climate sensitivity of 4.5 rather than > the established IPCC value of 3.0 that is (as I understand it) embedded in > most current climate models, is excellent and should be widely distributed, > per these last two paragraphs: > > "Criticisms of the Acceleration paper in the media did not address the > physics in our three assessments of > climate sensitivity. Instead, criticisms were largely ad hoc opinions, > even ad hominem attacks. How can > science reporting have descended to this level? Climate science is now so > complex, with many sub- > disciplines, that the media must rely on opinions of climate experts. > Although there are thousands of > capable scientists in these disciplines, the media have come to depend on > a handful of scientists, a clique > of climate scientists who are willing, or even eager, to be the voice of > the climate science community. > But are they representative of the total community, of capable scientists > who focus on climate science? > We have lamented9 the absence of scientists with the breadth of > understanding of say Jule Charney or > Francis Bretherton,10 or our beloved, sometimes crotchety, former > colleague, Wally Broecker. However, > the truth is that there are many scientists out there with a depth of > understanding at least as great as the > clique of scientists that the media rely on. Given the success of this > clique in painting us as outliers, we > are dependent on the larger community being willing to help educate the > media about the current climate > situation. For that purpose, we will discuss – one-by-one in upcoming > communications – several of the > matters that are raised in our papers. Thanks for your attention." > > @Dan: Thanks for sharing! I will definitely give this a listen! > > Best, > Ron > > > On Sun, May 18, 2025 at 4:04 PM LDM <[email protected]> wrote: > >> >> https://www.columbia.edu/~jeh1/mailings/2025/CloudFeedback.13May2025.pdf >> >> Large Cloud Feedback Confirms High Climate Sensitivity >> James Hansen and Pushker Kharecha >> 13 May 2025 >> >> Abstract. >> >> Earth’s albedo (reflectivity) declined over the 25 years of precise >> satellite data, with the decline so large that this change must be mainly >> reduced reflection of sunlight by clouds. Part of the cloud change is >> caused by reduction of human-made atmospheric aerosols, which act as >> condensation nuclei for cloud formation, but most of the cloud change is >> cloud feedback that occurs with global warming. The observed albedo change >> proves that clouds provide a large, amplifying, climate feedback. This >> large cloud feedback confirms high climate sensitivity, consistent with >> paleoclimate data and with the rate of global warming in the past century. >> >> >> https://youtu.be/NxV1IbHt7fU >> >> When Will We Go Over 2ºC? & Hansen's Cloud Update >> <https://www.youtube.com/@climatechat> >> >> >> On Sun, May 18, 2025 at 9:09 PM Ron Baiman <[email protected]> wrote: >> >>> Wow! Thanks for sharing Renaud. I haven't read it but from the >>> abstract it (very unfortunate for all of us humans and most other species, >>> but not really surprising for many of us humans) looks like forecasts of >>> Hansen et al. 2024 are being vindicated! >>> Best, >>> Ron >>> >>> >>> On Wed, May 14, 2025 at 9:51 AM Renaud de RICHTER < >>> [email protected]> wrote: >>> >>>> Earth's Energy Imbalance More Than Doubled in Recent Decades >>>> https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024AV001636 >>>> Abstract >>>> >>>> Global warming results from anthropogenic greenhouse gas emissions >>>> which upset the delicate balance between the incoming sunlight, and the >>>> reflected and emitted radiation from Earth. The imbalance leads to energy >>>> accumulation in the atmosphere, oceans and land, and melting of the >>>> cryosphere, resulting in increasing temperatures, rising sea levels, and >>>> more extreme weather around the globe. Despite the fundamental role of the >>>> energy imbalance in regulating the climate system, as known to humanity for >>>> more than two centuries, our capacity to observe it is rapidly >>>> deteriorating as satellites are being decommissioned. >>>> Key Points >>>> >>>> >>>> - >>>> >>>> Earth's energy imbalance more than doubled in recent decades >>>> - >>>> >>>> The large trend has taken us by surprise, and as a community we >>>> should strive to understand the underlying causes >>>> - >>>> >>>> Our capability to observe the Earth's energy imbalance and budget >>>> terms is threatened as satellites are decommissioned >>>> >>>> Plain Language Summary >>>> >>>> Global warming is caused by the imbalance between the incoming >>>> radiation from the Sun and the reflected and outgoing infrared radiation >>>> from the Earth. The imbalance leads to energy accumulation in the >>>> atmosphere, oceans and land, and melting of the cryosphere, resulting in >>>> increasing temperatures, rising sea levels, and more extreme weather around >>>> the globe according the the United Nations Intergovernmental Panel on >>>> Climate Change (IPCC). Observations from space of the energy imbalance >>>> shows that it is rising much faster than expected, and in 2023 it reached >>>> values two times higher than the best estimate from IPCC. We argue that we >>>> must strive to better understand this fundamental change in Earth's climate >>>> state, and ensure our capacity to monitor it in the future. >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "Healthy Planet Action Coalition (HPAC)" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to >>>> [email protected]. >>>> To view this discussion visit >>>> https://groups.google.com/d/msgid/healthy-planet-action-coalition/CAHodn9-e2iCfiPJYDRnv2TTcjgCueetUw9Fs83Tp48B2gA0jJA%40mail.gmail.com >>>> <https://groups.google.com/d/msgid/healthy-planet-action-coalition/CAHodn9-e2iCfiPJYDRnv2TTcjgCueetUw9Fs83Tp48B2gA0jJA%40mail.gmail.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> >>> >>> -- >>> Healthy Planet Action Coalition <http://www.healthyplanetaction.org> >>> YouTube Channel >>> <https://www.youtube.com/channel/UCdt5vatByfyg-Pm9Vu6ahZg> >>> @HPACoalition (Bluesky and Twitter/X) >>> Addressing the Urgent Need for Direct Climate Cooling: Rationale and >>> Options <https://academic.oup.com/oocc/article/4/1/kgae014/7731760> >>> Baiman et al. 2024. *Oxford Open Climate Change* >>> An Open Letter to the IMO Supporting Maritime Transport that Cools the >>> Atmosphere While Preserving Air Quality Benefits >>> <https://academic.oup.com/oocc/article/4/1/kgae008/7706251>. Baiman et >>> al. 2024. *Oxford Open Climate Change* >>> >> > > -- > Healthy Planet Action Coalition <http://www.healthyplanetaction.org> > YouTube Channel <https://www.youtube.com/channel/UCdt5vatByfyg-Pm9Vu6ahZg> > @HPACoalition (Bluesky and Twitter/X) > Addressing the Urgent Need for Direct Climate Cooling: Rationale and > Options <https://academic.oup.com/oocc/article/4/1/kgae014/7731760> > Baiman et al. 2024. *Oxford Open Climate Change* > An Open Letter to the IMO Supporting Maritime Transport that Cools the > Atmosphere While Preserving Air Quality Benefits > <https://academic.oup.com/oocc/article/4/1/kgae008/7706251>. Baiman et > al. 2024. *Oxford Open Climate Change* > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/geoengineering/CAPhUB9CnQHnNxxw0m238XK9mxSatsHedxndUf7vO0KoQkVeiXQ%40mail.gmail.com > <https://groups.google.com/d/msgid/geoengineering/CAPhUB9CnQHnNxxw0m238XK9mxSatsHedxndUf7vO0KoQkVeiXQ%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > -- > You received this message because you are subscribed to the Google Groups > "geoengineering" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/geoengineering/4e23a031-1d90-429f-b962-a428e82fc7ac%40comcast.net > <https://groups.google.com/d/msgid/geoengineering/4e23a031-1d90-429f-b962-a428e82fc7ac%40comcast.net?utm_medium=email&utm_source=footer> > . > -- Jim Hansen, Director Climate Science, Awareness and Solutions Program Columbia University Earth Institute -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/geoengineering/CAEL%2B3vM1eBgxrNdGNjtUOKv75kMx43UgfVnEu-T06SL7wOhYDQ%40mail.gmail.com.
