Chris Nelder 🤘Jul 25, 2023

The climate freak-out du jour is, typically, horribly misrepresenting a very technical paper about the AMOC. E.g., if you read this https://www.theguardian.com/environment/2023/jul/25/gulf-stream-could-collapse-as-early-as-2025-study-suggests?CMP=Share_AndroidApp_Other you'll get a clear sense that the climate will soon pass a "tipping point" and "The Gulf Stream system could collapse as soon as 2025" or worse - as one person said, "The North Atlantic Conveyor is going to fail over the next decade."

That is not exactly what the paper says.

1/2

Gulf Stream could collapse as early as 2025, study suggests

A collapse would bring catastrophic climate impacts but scientists disagree over the new analysis

The Guardian
Show threadChris Nelder 🤘Jul 25, 2023

Prof. Stefan Rahmstorf has a much more accurate take: https://www.realclimate.org/index.php/archives/2023/07/what-is-happening-in-the-atlantic-ocean-to-the-amoc/

His conclusion:
"Timing of the critical AMOC transition is still highly uncertain, but increasingly the evidence points to the risk being far greater than 10 % during this century – even rather worrying for the next few decades. The conservative IPCC estimate, based on climate models which are too stable and don’t get the full freshwater forcing, is in my view outdated now."

And we need to take climate action. 2/2

RealClimate: What is happening in the Atlantic Ocean to the AMOC?

RealClimate: For various reasons I'm motivated to provide an update on my current thinking regarding the slowdown and tipping point of the Atlantic Meridional Overturning Circulation (AMOC). I attended a two-day AMOC session at the IUGG Conference the week before last, there's been interesting new papers, and in the light of that I have been changing

RealClimate | Climate science from climate scientists...
Show threadChris Nelder 🤘Jul 25, 2023

PS: At the end of Rahmstorf's post, he links to a 2022 OECD report on climate "tipping points" which are helpfully summarized in this table: https://www.oecd-ilibrary.org/sites/abc5a69e-en/1/3/2/index.html?itemId=/content/publication/abc5a69e-en&_csp_=6d00888f3885b1fcadfb107c6ede4c51&itemIGO=oecd&itemContentType=book#tablegrp-d1e1196

As that table shows, both the words "tipping" (as in, to a new, *irreversible* state) and "point" (as in, not a range of uncertainty) are highly questionable, and IMO, unhelpful.

I.e., a 10% chance of an AMOC transition happening this century is a VERY different thing than the Gulf Stream (?!) collapsing in two years.

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Show threadChris Nelder 🤘Jul 26, 2023

Here's a good, nuanced, accurate comment on the new AMOC paper from Prof Penny Holliday, the head of an international programme researching AMOC, correcting some errors in the paper and the press release about it: https://www.sciencemediacentre.org/expert-reaction-to-paper-warning-of-a-collapse-of-the-atlantic-meridional-overturning-circulation/

"there are some assumptions in the methodology which means that the results are not be quite as solid as the title and abstract suggest"

expert reaction to paper warning of a collapse of the Atlantic meridional overturning circulation | Science Media Centre

Show threadChris Nelder 🤘Jul 26, 2023

... to wit, "A collapse of the AMOC would profoundly impact every person on Earth but this study overstates the certainly in the likelihood of it taking place within the next few years... the title of the paper is more sensational than the actual statements within it."

As is most of the press coverage you read about it yesterday!

Show threadChris Nelder 🤘
..."As mentioned above, the actual observations of AMOC since 2004 have long-since discredited the evidence that the authors are using to validate their modified SST temperature record. The 5 data points they show in the paper were collected several years apart by ship surveys, and it is well known and well established that they give a highly misleading impression of AMOC decline. All the observational evidence we have shows no evidence of dramatic decline in the AMOC over the past 50-75 years."
Jul 26, 2023 at 5:33pmWeb