Ed. note: A recent peer-reviewed article in Nature (discussed here) has, once again, knocked this speculative “fat tail” hypothesis down to size. “Based on the here identified relationship and observation-based estimates of the past air-sea heat flux in the North Atlantic from reanalysis products,” the authors concluded, “the decadal averaged AMOC at 26.5°N has not weakened from 1963 to 2017 although substantial variability exists at all latitudes.”
Climate alarm is the name of the game for the government-led Climate Industrial Complex to keep the taxpayer grants going to the wind, solar, and battery rent-seekers. Nature is optimal and fragile, and the game is to throw hypotheticals against the wall to see what might stick. The mainstream media is hungry for a scary scenario too.
One perennial fear is a potential collapse of a crucial system of ocean currents known as the Atlantic Meridional Overturning Circulation (AMOC). A few scientists are ‘out there’ predicting an increasing chance of a collapse, but the consensus leans the other way. [1]
Forty-four scientists, including Michael “Climategate” Mann, published an open letter with ominous implications. “Recent research since the last IPCC report does suggest that the IPCC has underestimated this risk and that the passing of this tipping point is a serious possibility already in the next few decades,” the letter states. The missive closes with a call to action:
Recognizing that adaptation to such a severe climate catastrophe is not a viable option, we urge the Council of Nordic Ministers to (a) initiate an assessment of this significant risk to the Nordic countries and (b) take steps to minimize this risk as much as possible. This could involve leveraging the strong international standing of the Nordic countries to increase pressure for greater urgency and priority in the global effort to reduce emissions as quickly as possible, in order to stay close to the 1.5 °C target set by the Paris Agreement.
The media loved it. “Key Atlantic current could collapse soon, ‘impacting the entire world for centuries to come,’ leading climate scientists warn,” wrote Sascha Pare in LiveScience. “How much should you worry about a collapse of the Atlantic conveyor belt?,” asked Bob Henson at Yale Climate Connections.
Carl Wunsch Rebuttal
Are the risks of a collapse of the dominant mechanism of northward heat transport in the North Atlantic, ushering in record cold, a real threat? Has it been “greatly underestimated” as the above letter states? In such instances, a good second opinion is needed, and Carl Wunsch of MIT is about as good as one can get.
I emailed Professor Wunsch with the query:
Many years ago, Dick Lindzen gave me your address to ask about the fear of a disruption of the conveyor belt in regard to the Atlantic Meridional Overturning Circulation. You expressed doubt back then.
This alarm is in the air today, and I wondered if you had some thoughts on this post (below) to share on LinkedIn where a debate is taking place.
Among the many reasons why we ought to cut climate-warming greenhouse gas emissions as quickly and sharply as possible, the weakening of a system of ocean currents known as the Atlantic Meridional Overturning Circulation, or AMOC, ranks high indeed. Several key scientificpapers over the last couple of years have put this long-percolating climate concern back on the front burner. It’s hard to overstate how widespread and calamitous the impacts could be if this conveyor belt were to collapse – and it’s a process that could begin in the next several decades, if the new work is on target.
He responded:
I’m aware of the fuss going on about the AMOC. Indeed I co-authored a paper about it not long ago (I’ve attached it). It’s somewhat technical.
To clarify however: I am *not* a climate skeptic, and I regard the threat of major climate change as very real and very worrisome. In that context, one can argue that alarming the public about elements such as the behavior of the AMOC could lead to useful actual political and scientific/engineering progress and precautions.
Where I become conflicted is when the particular science is mis-interpreted and mis-understood. Turning the AMOC on and off as an explanation of major past and possible future change has become a go-to-story for people who want a simple explanation of a very complicated system. [Wallace] Broecker [here] did the world a great dis-service with his advocacy of the “conveyor belt” which leads people to think they understand a system which looks nothing like his picture (a memorable graphic however).
There are lots of issues connected with the fuss over the AMOC. Amongst them, prominently, are the use of numerical models which produce ocean circulations that are far from what we actually observe. How seriously should one take their “predictions”? That the climate can change dramatically from what we have known for the last several hundred years is a fact, and a very worrisome fact at that. Does that mean the AMOC stories in the media are correct?
Climate is a global phenomenon. Consider a hypothetical situation: turn the North Atlantic Ocean abruptly into all land. Zero AMOC; removal of a major current system. How does the climate system adjust? At the present time, the Earth is in near thermal balance (radiation incoming from the sun is almost equal to that radiated back to space—the small excess of incoming over outgoing is the global warming phenomenon). Physics suggests that the system would adjust to the removal of the North Atlantic by ultimately re-establishing global near-heat balance.
How does that happen? Change in clouds? Change in ocean circulation? Change in distribution of ice sheets? Change in atmospheric circulation? All global. How long does it take (years, decades, centuries)? What will the climate be like during the transition? We do not have numerical models with the demonstrated skill to answer such questions. Could be terrible, however. Suppression of the AMOC, should it happen, raises precisely the same global questions with the added complication that the North Atlantic circulation itself would also change.
Isn’t it worth taking some precautions? It’s an insurance problem in the same sense that I would rewire my house if an electrician told me that the existing wiring could cause a fire (not that a fire *will* happen; only that we know it could).
Comment
We live at a time when climate scientists do not want to be labeled a skeptic or denier, yet honest scientists are still doing their duty to weigh in against undue alarmism. (Note the beginning and end of Wunch’s replay above.)
Also note that how the Deep Ecology notion of an optimal, stable, fragile climate is the default thinking of so many natural scientists. The idea that the human influence on climate could be positive and even a ‘fat tail’ good (such as cancelling out a series of volcanoes or a natural global cooling) is not part of the analysis.
[1] Atlantic Meridional Overturning Circulation (AMOC) describes the movement of water from north to south and back south to north in the Atlantic Ocean. This circulation is responsible for warmth in different parts of the world and carries essential nutrients for ocean life.
The question is whether this (very slow) process is slowing down because of anthropogenic warming of the water, which would cause droughts in South Africa and sea level rise in the eastern U.S.
Source: What is the Atlantic Meridional Overturning Circulation (AMOC)?
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January 23, 2025 at 01:06AM
