Chris Nelder 🤘

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
Jul 25, 2023 at 10:02pmWeb
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IPCC estimate, based on climate models which are too stable and don’t get the full freshwater forcing, is in my view outdated now."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 🤘Jul 26, 2023
..."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."
Show threadKevin LeecasterJul 26, 2023
@chrisnelder
Mainstream and social media reporting on our #ClimateCrisis for the most part probably is causing more harm than good sadly it seems.
Show threadJim SmootJul 25, 2023
@chrisnelder the climate models are/were too conservative. This was obvious when “spike” experiments resulted in less arctic sea loss than observed with present carbon dioxide levels. Folks at UCSD reported this a few years ago and are working on improving model sensitivity afaik.
Show threadChris Nelder 🤘Jul 25, 2023
@jim_smoot Good to know.
Show threadteledyn 𓂀Jul 25, 2023

@jim_smoot

Does it help when #cop28 will be chaired by an oil exec?

https://www.lemonde.fr/en/environment/article/2023/01/12/cop28-sultan-al-jaber-ceo-of-a-uae-oil-company-appointed-president_6011348_114.html

@chrisnelder

COP28: Sultan al-Jaber, CEO of a UAE oil company, appointed conference president

The appointment of the UAE minister for industry and CEO of the Abu Dhabi National Oil Company, officially announced on Thursday, January 12, has been met with disbelief by many climate experts.

Le Monde
Show threadJim SmootJul 25, 2023
@teledyn @chrisnelder undoubtedly! /sarcasm However, cop is but one level of engagement, and focusing on ways to accelerate ff demand destruction is best use of time imo.
Show threadSmokeyGeoJul 26, 2023
@chrisnelder who is "we?" It seems to be doing a lot of work here. Any chance this report will be persuasive to Putin getting him to call off his emissions-increasing war not to mention shoddy practices by Gazprom? Or getting Chinese/ Indians to stop building 1+ coal plants per week?
Show threadJohn StonierJul 26, 2023

@chrisnelder
Indeed!

" the models used have coarse resolution and are not adept at analysing the non-linear processes involved, which may make them overly conservative."

Show threadljboJul 26, 2023
@chrisnelder The crux is the paragraph just before that conclusion imho. ⤵️ First it is the source of year 2025 in The Guardian. Then near certainty of a tipping point this century and a most probable time around 2050, this is too close for my comfort!
Show threadKim Spence-Jones 🇬🇧😷Jul 26, 2023
@chrisnelder Whether or not predictions of the collapse of the Gulf Stream are accurate is not really important. That’s like discussing the exact ratio of bullets to chambers in the revolver when you’re playing Russian Roulette. The real point is that the worst-case scenario is so fatal that we’re crazy even to be considering taking the risk.