There”s a paper in Nature, Warning of a forthcoming collapse of the Atlantic meridional overturning circulation, which certainly sounds alarming. Science Media Centre has an article that’s just a...
I got you bro. Reproduced in full below. Only formatting change has been to indent, rather than italicize, block-quoted material so that it stands out in comparison to the question subheaders....
Exemplary
I got you bro. Reproduced in full below. Only formatting change has been to indent, rather than italicize, block-quoted material so that it stands out in comparison to the question subheaders.
Prof Penny Holliday, Head of Marine Physics and Ocean Circulation at the National Oceanography Centre, and Principal Investigator for OSNAP, an international programme researching AMOC processes, variability and impacts, said:
“Confidence in the validity of the conclusions are undermined by our knowledge that sea surface temperature of the North Atlantic subpolar gyre is not a clear indicator of the state of the AMOC, and that there is no evidence that the AMOC has dramatically weakened in the past 50-75 years. 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.”
Does the press release accurately reflect the science?
“On the whole it does – the title of the paper is more sensational than the actual statements within it, and the press release does make that clear. However there are two statements that are not accurate as follows:
‘The strength of the AMOC has only been monitored continuously since 2004 and these observations have shown AMOC to be weakening’
“This is stated in the paper but it is not correct information. The observations since 2004 show that the AMOC goes through fluctuations of being in a stronger or weaker state that last for about 10 years. The observations since 2004 show the subtropical AMOC getting slower from 2004 to 2012, but gradually becoming stronger since then. The only data from AMOC observations shown in the paper are from 5 sparse ship surveys and are used out of context – the authors use them to argue for a severe decline in the AMOC, but that interpretation has long been discredited in the scientific literature (including in the reference they cite for it).
‘The authors found early warning signals of a critical transition of the AMOC system and suggest that it could shut down or collapse as early as 2025 and no later than 2095.’
“This is not quite as the paper states. In the paper the time period of potential collapse depends on choices they have made in how they construct the time series of sea surface temperature which they use as evidence for change. They present three versions of the temperature records, and the three resulting model predictions suggests a collapse is ‘likely’ at any time from 2024 to 2180. The 2025-2095 is the period of time their statistical model predicts that a full or partial collapse is most likely.
Is this good quality research? Are the conclusions backed up by solid data?
“The use of statistical models to test whether a tipping point can be detected is something that previous authors have done using datasets from climate models. So the approach is valid, and the topic is of great interest because of the potentially very serious climate impacts that a collapse of an AMOC would bring to the world. However there are some assumptions in the methodology which means that the results are not be quite as solid as the title and abstract suggest (see below). The authors acknowledge in the Discussion that there is large uncertainty in their conclusions.
How does this work fit with the existing evidence?
“The conclusions are different to the consensus derived from climate projections as described by the IPCC AR6 assessment. The averaged AMOC projections from climate models under all the IPCC emissions scenarios all show an AMOC decline, but not a collapse (a “high confidence” conclusion). Some individual climate model runs do show a future collapse in the AMOC, so the possibility cannot be entirely ruled out.
Are there any important limitations to be aware of?
“There are some questionable assertions and decisions in the methods as follows. The authors state confidently that the sea surface temperature (SST) of the North Atlantic subpolar gyre can be used as a proxy for the strength of the AMOC. The validity of an SST proxy for AMOC strength is a matter of ongoing scientific debate however, because it is based on model behaviour and is not proven using real-world data. There is solid evidence that there is no such clear relationship, especially on timescales of less than 30 years.
“I believe the authors have overstated the pattern of subpolar North Atlantic SST change by subtracting two (and three) times the global mean surface temperature trend. This is not the usual approach for highlighting North Atlantic regional temperature trend (instead it is more usual to subtract just 1 x the global trend). The choice means that some of the SST data they use in the statistical model has exaggerated decline since the 1970s when the global SST began to sharply rise. In the version of the statistical model for which the global mean SST trend is removed, the predicted likely time of a partial or complete collapse becomes later and over a wider window of time.
“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.
How uncertain are the uncertainties?
“The authors say that the model’s 95% confidence interval is 2025-2095. This is a measure of statistical uncertainty and they state in the discussion that they cannot rule out slowing rather than a collapse, as well as listing other reservations and caveats. Because of the limitations of their use of modified SST as a proxy for AMOC, the uncertainty in the stated message in the title and abstract is high.
What are the implications in the real world?
“The potential for the AMOC system of currents to collapse under global warming is a high impact, low likelihood scenario, and policymakers and planners do need to be aware of it. NOC and international partners are investing in ongoing observations of the AMOC in order to determine how closely changes in AMOC contribute to changes in SST and consequential climate and social and economic impacts on people. The strength of the out-of-sight ocean currents of the AMOC has surprisingly direct impacts on food, water and energy security, infrastructure risk, biodiversity, and human health. The paper demonstrates that decades of observations are needed to be able to detect a major tipping point in the AMOC, and the authors call for continued measurements of these great Atlantic ocean currents for long enough to do so.
What are the tangible impacts of a collapse?
“The AMOC carries huge amounts of heat northwards through the whole Atlantic Ocean, setting climate conditions for all the Earth’s continents. If it switched off, the result after a few decades would be much lower surface temperatures and stronger winds across the whole northern hemisphere (land and ocean). Heat would pool in the Southern Ocean and South Atlantic, but over the southern continents, temperatures would also decrease. Major rainfall zones would shift, leading to far less rainfall over Europe, North and Central America, north and central Africa and Asia, and more over the Amazon, Australia and southern Africa. Sea ice would extend southwards from the Arctic into the subpolar North Atlantic, and the Antarctic sea ice would extend northwards. For people and governments this would lead to dramatic change in every nation’s ability to provide enough food and water for its population. Energy supply and demand would change rapidly with new climate conditions and infrastructures would need heavy investment to adapt and cope. The patterns of vector-borne disease and health (including mental health) would be profoundly affected. World-wide many land and marine ecosystems would be unable to cope and adapt to such fast changing climate conditions and biodiversity would be severely impacted.
Is there any overspeculation?
“The authors are appropriately careful not to overspeculate in the text, although the title of the paper and the text of the abstract is rather more dramatic and conveys a more certain outcome than the authors actually write in the results and discussion. They describe the potential for AMOC collapse within a few years as “worrisome” and the evidence as something that we should not ignore. It’s hard to disagree with that.”
I'm so saddened. I wish important articles/opinions like this were more available and accepted in the 80's, and then immediate action was then taken as we could have avoided many of the feedback...
I'm so saddened. I wish important articles/opinions like this were more available and accepted in the 80's, and then immediate action was then taken as we could have avoided many of the feedback loops that we are experiencing now.
This is a really nice article. I remember when the latest IPCC physics report came out reading (and re-reading) the sentence that there was medium confidence that there wouldn’t be a catastrophic...
This is a really nice article. I remember when the latest IPCC physics report came out reading (and re-reading) the sentence that there was medium confidence that there wouldn’t be a catastrophic collapse of the AMOC. I’m an ecologist who works with climate change related stuff regularly, but something about that sentence really hit me in a way I didn’t think climate change forecasts could any more. Like. Holy shit. The apocalyptic scenarios are legit plausible.
From Prof Jeffery Kargel: Hmmm so we(1) might be able to just hunker down and get over it in a few hundred years time. No matter how hostile and awful life becomes in north american and Europe,...
From Prof Jeffery Kargel:
“Many scientists have examined this climate-critical part of the Earth and have found evidence for occasional weakening and shut down of AMOC, then re-establishment after several centuries.
Hmmm so we(1) might be able to just hunker down and get over it in a few hundred years time. No matter how hostile and awful life becomes in north american and Europe, earth will still be way more livable than mars for a few centuries.
(1) for some values of "we". Hopefully animals and maybe even some humans
There”s a paper in Nature, Warning of a forthcoming collapse of the Atlantic meridional overturning circulation, which certainly sounds alarming. Science Media Centre has an article that’s just a bunch of reactions from scientists. Imagine a comment section that was actually well-informed?
I liked the response from Prof. Penny Holiday. Sadly, the whole thing seems to be blocked by an image so I can’t easily quote it from my tablet.
I got you bro. Reproduced in full below. Only formatting change has been to indent, rather than italicize, block-quoted material so that it stands out in comparison to the question subheaders.
Prof Penny Holliday, Head of Marine Physics and Ocean Circulation at the National Oceanography Centre, and Principal Investigator for OSNAP, an international programme researching AMOC processes, variability and impacts, said:
“Confidence in the validity of the conclusions are undermined by our knowledge that sea surface temperature of the North Atlantic subpolar gyre is not a clear indicator of the state of the AMOC, and that there is no evidence that the AMOC has dramatically weakened in the past 50-75 years. 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.”
Does the press release accurately reflect the science?
“On the whole it does – the title of the paper is more sensational than the actual statements within it, and the press release does make that clear. However there are two statements that are not accurate as follows:
“This is stated in the paper but it is not correct information. The observations since 2004 show that the AMOC goes through fluctuations of being in a stronger or weaker state that last for about 10 years. The observations since 2004 show the subtropical AMOC getting slower from 2004 to 2012, but gradually becoming stronger since then. The only data from AMOC observations shown in the paper are from 5 sparse ship surveys and are used out of context – the authors use them to argue for a severe decline in the AMOC, but that interpretation has long been discredited in the scientific literature (including in the reference they cite for it).
“This is not quite as the paper states. In the paper the time period of potential collapse depends on choices they have made in how they construct the time series of sea surface temperature which they use as evidence for change. They present three versions of the temperature records, and the three resulting model predictions suggests a collapse is ‘likely’ at any time from 2024 to 2180. The 2025-2095 is the period of time their statistical model predicts that a full or partial collapse is most likely.
Is this good quality research? Are the conclusions backed up by solid data?
“The use of statistical models to test whether a tipping point can be detected is something that previous authors have done using datasets from climate models. So the approach is valid, and the topic is of great interest because of the potentially very serious climate impacts that a collapse of an AMOC would bring to the world. However there are some assumptions in the methodology which means that the results are not be quite as solid as the title and abstract suggest (see below). The authors acknowledge in the Discussion that there is large uncertainty in their conclusions.
How does this work fit with the existing evidence?
“The conclusions are different to the consensus derived from climate projections as described by the IPCC AR6 assessment. The averaged AMOC projections from climate models under all the IPCC emissions scenarios all show an AMOC decline, but not a collapse (a “high confidence” conclusion). Some individual climate model runs do show a future collapse in the AMOC, so the possibility cannot be entirely ruled out.
Are there any important limitations to be aware of?
“There are some questionable assertions and decisions in the methods as follows. The authors state confidently that the sea surface temperature (SST) of the North Atlantic subpolar gyre can be used as a proxy for the strength of the AMOC. The validity of an SST proxy for AMOC strength is a matter of ongoing scientific debate however, because it is based on model behaviour and is not proven using real-world data. There is solid evidence that there is no such clear relationship, especially on timescales of less than 30 years.
“I believe the authors have overstated the pattern of subpolar North Atlantic SST change by subtracting two (and three) times the global mean surface temperature trend. This is not the usual approach for highlighting North Atlantic regional temperature trend (instead it is more usual to subtract just 1 x the global trend). The choice means that some of the SST data they use in the statistical model has exaggerated decline since the 1970s when the global SST began to sharply rise. In the version of the statistical model for which the global mean SST trend is removed, the predicted likely time of a partial or complete collapse becomes later and over a wider window of time.
“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.
How uncertain are the uncertainties?
“The authors say that the model’s 95% confidence interval is 2025-2095. This is a measure of statistical uncertainty and they state in the discussion that they cannot rule out slowing rather than a collapse, as well as listing other reservations and caveats. Because of the limitations of their use of modified SST as a proxy for AMOC, the uncertainty in the stated message in the title and abstract is high.
What are the implications in the real world?
“The potential for the AMOC system of currents to collapse under global warming is a high impact, low likelihood scenario, and policymakers and planners do need to be aware of it. NOC and international partners are investing in ongoing observations of the AMOC in order to determine how closely changes in AMOC contribute to changes in SST and consequential climate and social and economic impacts on people. The strength of the out-of-sight ocean currents of the AMOC has surprisingly direct impacts on food, water and energy security, infrastructure risk, biodiversity, and human health. The paper demonstrates that decades of observations are needed to be able to detect a major tipping point in the AMOC, and the authors call for continued measurements of these great Atlantic ocean currents for long enough to do so.
What are the tangible impacts of a collapse?
“The AMOC carries huge amounts of heat northwards through the whole Atlantic Ocean, setting climate conditions for all the Earth’s continents. If it switched off, the result after a few decades would be much lower surface temperatures and stronger winds across the whole northern hemisphere (land and ocean). Heat would pool in the Southern Ocean and South Atlantic, but over the southern continents, temperatures would also decrease. Major rainfall zones would shift, leading to far less rainfall over Europe, North and Central America, north and central Africa and Asia, and more over the Amazon, Australia and southern Africa. Sea ice would extend southwards from the Arctic into the subpolar North Atlantic, and the Antarctic sea ice would extend northwards. For people and governments this would lead to dramatic change in every nation’s ability to provide enough food and water for its population. Energy supply and demand would change rapidly with new climate conditions and infrastructures would need heavy investment to adapt and cope. The patterns of vector-borne disease and health (including mental health) would be profoundly affected. World-wide many land and marine ecosystems would be unable to cope and adapt to such fast changing climate conditions and biodiversity would be severely impacted.
Is there any overspeculation?
“The authors are appropriately careful not to overspeculate in the text, although the title of the paper and the text of the abstract is rather more dramatic and conveys a more certain outcome than the authors actually write in the results and discussion. They describe the potential for AMOC collapse within a few years as “worrisome” and the evidence as something that we should not ignore. It’s hard to disagree with that.”
I'm so saddened. I wish important articles/opinions like this were more available and accepted in the 80's, and then immediate action was then taken as we could have avoided many of the feedback loops that we are experiencing now.
But if wishes were fishes, etc etc
This is a really nice article. I remember when the latest IPCC physics report came out reading (and re-reading) the sentence that there was medium confidence that there wouldn’t be a catastrophic collapse of the AMOC. I’m an ecologist who works with climate change related stuff regularly, but something about that sentence really hit me in a way I didn’t think climate change forecasts could any more. Like. Holy shit. The apocalyptic scenarios are legit plausible.
From Prof Jeffery Kargel:
Hmmm so we(1) might be able to just hunker down and get over it in a few hundred years time. No matter how hostile and awful life becomes in north american and Europe, earth will still be way more livable than mars for a few centuries.
(1) for some values of "we". Hopefully animals and maybe even some humans