Ocean current collapse predicted--2025 to 2095

Previous study said not before 2100.

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From the link:

“Scientists uninvolved with this study told CNN the exact tipping point for the critical system is uncertain, and that measurements of the currents have so far showed little trend or change.

DB2

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Fraser and Cunningham reconstructed the AMOC (Atlantic Meridional Overturning Circulation) back to 1900. Looking at their Figure 3, it can be seen that the current strength is now where it was in 1910 and stronger than it was in 1900 and 1970.

120 Years of AMOC Variability Reconstructed From Observations Using the Bernoulli Inverse
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2021GL093893
DB2

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Here is the whole paragraph when in context gives a different impression from the above:

“Scientists uninvolved with this study told CNN the exact tipping point for the critical system is uncertain, and that measurements of the currents have so far showed little trend or change. But they agreed these results are alarming and provide new evidence that the tipping point could occur sooner than previously thought.

Now you might ask why would they find anything alarming if currents aren’t changing? It’s because there is a lot of uncertainty about those currents.

Direct measurements of the AMOC have only been made for about 20 years, during which there can be seen a downward trend. However, climate studies require much longer time frames and these can only be estimated using indirect physical measures called proxies. DrBob links to one using something called the Bernoulli inverse method that indicates no significant change in the AMOC over 120 years. However, that same paper also states that other methods do show a significant decline in the current:

" Longer AMOC time series estimates have been generated using proxies such as surface temperature (Caesar et al., 2018; Rahmstorf et al., 2015), sediment cores (Thornalley et al., 2018) or coastal surface height (McCarthy, Haigh, et al., 2015). Caesar et al. (2021) showed that a coherent decline is evident during the 20th century in numerous AMOC proxies, suggesting the AMOC has weakened exceptionally since the onset of the industrial era."

The paper in the OP that warns of an AMOC collapse is based on historical sea surface temperatures and validated by ensemble climate model simulations. It represents the most recent extrapolation of AMOC trends.

In summary what you have are conflicting estimations of the behavior of a critical ocean current system that could have enormous consequences on global climate. Most estimations, including the most recent analysis indicate a significant slowing of the AMOC leading to an eventual collapse. The most recent analysis indicates a high probability that this collapse will occur in this century.

Suppose there were 10 safety inspections of a plane. Four said it was safe to fly while the remainder disagreed. Would you load your family onto the plane?

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I would say it is still an area of research without a definitive conclusion. There are periods of strengthening and weakening with large interannual and decadal variability.

Here is another long-term study, this one going back to 1860.
https://www.sciencedirect.com/science/article/pii/S246801331500008X
“By using tide gauge data complementing recent satellite and ocean sensor observations, the stability of the AMOC is shown to go back to 1860. It is concluded that no available information has the due accuracy and time coverage to show a clear trend outside the inter-annual and multi-decadal variability in the direction of increasing or decreasing strength over the last decades.”

DB2

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Certainly no “scientific consensus”. The question though is given the data at hand, is this something we should be concerned about? Unfortunately, it is not sufficient to say to wait until definitive evidence is obtained since it is likely that if there is a problem it will be too late by then to do much about it.

The question then is not whether the data is conclusive, it is not. The question is whether there is sufficient evidence to justify taking action to reduce the risk of the potential problem. I think there is.

It is a bit like the threat of China invading Taiwan. Do we know that it is going to happen? Not at all. Is there sufficient risk of it happening that the US should take proactive steps in preparation of the possibility? That’s open to opinion, but it seems a prudent thing to do.

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Agreed. And that was the point of posting additional research to the OP.

DB2

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Experts not involved in this study offer mixed reviews of its conclusions. Michael Mann, of the University of Pennsylvania, said, “I’m not sure the authors bring much to the table other than a fancy statistical method. History is littered with flawed predictions based on fancy statistical methods; sometimes they’re too fancy for their own good.”

DB2

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Indeed in science we know that extrapolations are risky.

And mother nature seems to have a mind of her own. We wish she had read our text books.

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Suppose you are a policy maker. What would you do with this extrapolation? You could take it seriously and accelerate mitigation efforts. Or you could ignore it as alarmist. Or you could decide to wait for more data, which is effectively ignoring it as alarmist.

What do you do?

I think you recognize this is yet another aspect of global warming.

Politicians should continue their global warming programs and accelerate them as best they can.

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Can we trust projections of AMOC weakening based on climate models that cannot reproduce the past?
https://royalsocietypublishing.org/doi/pdf/10.1098/rsta.2022.0193
“We show that both the magnitude of the trend in the AMOC over different time periods and often even the sign of the trend differs between observations and climate model ensemble mean, with the magnitude of the trend difference becoming even greater when looking at the CMIP6 ensemble compared to CMIP5.”

DB2

Interesting analogy. I am expecting the EU to stop a lot of international air travel to Europe.

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