Comments 1 to 7:

1. sailrick at 14:20 PM on 27 July, 2020

   I admit I haven't read the article on climate sensitivity, but I'm confused. I read two other articles about the new study and they said 2.6-4.1 C was the new range.  

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2. One Planet Only Forever at 14:34 PM on 27 July, 2020

   sailrick,

   I also have not bought the article to read it. But the available abstract includes the following statement to indicate that several different, but similar ranges for S could be presented.

   "The 66% range is 2.6‐3.9 K for our Baseline calculation, and remains within 2.3‐4.5 K under the robustness tests; corresponding 5‐95% ranges are 2.3‐4.7 K, bounded by 2.0‐5.7 K (although such high‐confidence ranges should be regarded more cautiously)."

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3. nigelj at 17:30 PM on 27 July, 2020

   Some free details and opinions on the new climate sensitivity study here.

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4. MA Rodger at 19:44 PM on 27 July, 2020

   nigelj @3,

   And that RealClimate OP thread does contain this link accessing the full paper.

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5. John Hartz at 23:49 PM on 27 July, 2020

   The most definitive article about the reserch findings is most likely the one writen by the paper's authors and posted on Carbon Brief. Here's the introduction to the article...

   After four years of labour and detailed discussions by an international team of scientists, we are able to quantify better than ever before how the world’s surface temperature responds to increasing CO2 levels.

   Our findings, published in Reviews of Geophysics, narrow the likely range in “equilibrium climate sensitivity” (ECS) – a measure of how much the world can be expected to warm for a doubling of CO2 above pre-industrial levels.

   Constraining ECS has remained a holy grail in climate science ever since US meteorologist Jules Charney suggested a possible range of 1.5C to 4.5C in his 1979 report. His estimate was largely based on the world’s first two global climate models, which gave different estimates of 2C and 4C when they performed a simple experiment where atmospheric CO2 levels were doubled.

   Since then, despite more than 40 years of research, much improved understanding of atmospheric processes, as well as many more detailed observations, this range has stubbornly persisted.

   Now, bringing together evidence from observed warming, Earth’s distant past and climate models, as well as advances in our scientific understanding of the climate, our findings suggest that the range of ECS is likely to be between 2.6C and 4.1C.

   This narrowed range indicates that human society will not be able to rely on a low sensitivity to give us more time to tackle climate change. But the silver lining to this cloud is that our findings also suggest that very high ECS estimates are unlikely.

   Guest post: Why low-end ‘climate sensitivity’ can now be ruled out by Piers Forster, Zeke Hausfather, Gabi Hegerl, Steven Sherwood & Kyle Armour, Carbon Brief, June 22, 2020

   Note: This article will be reposted in its entirety on this website later this week.

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6. sailrick at 01:52 AM on 30 July, 2020

   Thanks for the clarifications. The Carbon Brief article was one the two I had read.

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7. wayne19608 at 02:11 AM on 30 July, 2020

   Sailrick, I kind of agree with you. It's more a ruling out of low end then high end states. Personally I will place more importance on the paleontological evidence. If we're 1C+/- now

   + 0.2C for the pre-preindustrial warming 

   + 0.5C for aerosols

   plus you have a 30year/66% lag meaning the temperatures were experiencing now are more indicative of 350ppm than 420ppm. So I see your point on how a +40% increase in CO2 has in all probability commited us to +2C rise in 150yrs. This doesn't address what the end state will be in 1000yrs or more. Now instead of a 40% increase imagine an actual doubling its obvious that a 2C warming shouldn't even be in the equation

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