Critic says ‘much speculation’ as Hansen-led paper attempts to revive the fading AMOC climate scare

A portion of the Atlantic meridional overturning circulation (AMOC) [image credit: R. Curry, Woods Hole Oceanographic Institution @ Wikipedia]

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Well-known alarmist James Hansen is again trying to crank up the anxiety levels of climate obsessives, with a new paper predicting a ‘likely’ oceanic nasty (AMOC shutdown) within a few decades unless more so-called action is taken by humans to supposedly control global warming. Recent studies finding the AMOC [Atlantic meridional overturning circulation] has been stable over recent decades, and that the very idea of climate ‘tipping points’ is overrated (links here), are ignored or rejected by the new paper. In addition, the recent Nikolov and Zeller paper (link here, see section 4) showing that the meaning of Earth’s energy imbalance (EEI) has been badly misunderstood, is not considered, but EEI is used in the Hansen paper’s analysis which talks of a ‘point of no return’.
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A study published in Environment: Science and Policy for Sustainable Development looks at shipping aerosol emissions and the rate of global warming, says the Science Media centre.

Dr Karsten Haustein, Climate Scientist, Leipzig University, said:

“Jim Hansen and colleagues have revisited the topic of aerosol-induced warming due to reduced shipping emissions (due to regulatory changes in 2020). It’s a more credible attempt than their last – rather disappointing – effort, but there is still much speculation involved.

“They estimate the global aerosol forcing from reduced shipping aerosols might be as high as 0.5 W/m2, which is far higher than the current estimates of 0.05-0.15 W/m2. They argue that Earth’s radiative imbalance as well as high levels absorbed solar radiation justify such assumption. Accordingly, they argue that Climate Sensitivity (temperature response after CO2 doubling in the atmosphere) might be as high as 4.5 W/m2.

“Given that Earth’s radiative imbalance has considerably come down in the 2nd half of 2024 (notwithstanding the uncertainties related to measuring the global radiative imbalance), I continue to remain skeptical of their claims. This is particularly true, as some of the extra warming could be traced to other internal factors that have not been discussed. The so-called ‘hiatus’ discussion in the 2010s should be an example of a cautionary tale. This is true all the more as we know with some certainty that CO2 and methane (CH4) forcing has continued to accelerate slightly, such that additional aerosol forcing increase is not necessarily required to explain what has happened in 2023 and 2024.

“They are correct in one aspect though: 2025 will prove whether there is more to the warming story than we thought.”
[Talkshop comment: two other scientists offer different opinions of the paper’s assertions].
. . .
‘Global Warming Has Accelerated: Are the United Nations and the Public Well-Informed?’ by James E. Hansen et al. was published in Environment: Science and Policy for Sustainable Development at 14:00 UK time on Tuesday 4 February 2025.
DOI: 10.1080/00139157.2025.2434494

Full article here.
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Image: A portion of the Atlantic meridional overturning circulation (AMOC) [credit: R. Curry, Woods Hole Oceanographic Institution @ Wikipedia]
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From the abstract of the Hansen et al paper:

Polar climate change has the greatest long-term effect on humanity, with impacts accelerated by the jump in global temperature. We find that polar ice melt and freshwater injection onto the North Atlantic Ocean exceed prior estimates and, because of accelerated global warming, the melt will increase. As a result, shutdown of the Atlantic Meridional Overturning Circulation (AMOC) is likely within the next 20-30 years, unless actions are taken to reduce global warming – in contradiction to conclusions of IPCC. If AMOC is allowed to shut down, it will lock in major problems including sea level rise of several meters – thus, we describe AMOC shutdown as the “point of no return.”