Is the Gulf Stream In Trouble?

A recent paper by researchers in Denmark has been getting a lot of notice this week. Here's the abstract. The key point is the last sentence.

The Atlantic meridional overturning circulation (AMOC) is a major tipping element in the climate system and a future collapse would have severe impacts on the climate in the North Atlantic region. In recent years weakening in circulation has been reported, but assessments by the Intergovernmental Panel on Climate Change (IPCC), based on the Climate Model Intercomparison Project (CMIP) model simulations suggest that a full collapse is unlikely within the 21st century. Tipping to an undesired state in the climate is, however, a growing concern with increasing greenhouse gas concentrations. Predictions based on observations rely on detecting early-warning signals, primarily an increase in variance (loss of resilience) and increased autocorrelation (critical slowing down), which have recently been reported for the AMOC. Here we provide statistical significance and data-driven estimators for the time of tipping. We estimate a collapse of the AMOC to occur around mid-century under the current scenario of future emissions.

From the New York Times (paywall-free link):

Were the circulation to tip into a much weaker state, the effects on the climate would be far-reaching, though scientists are still examining their potential magnitude. Much of the Northern Hemisphere could cool. The coastlines of North America and Europe could see faster sea-level rise. Northern Europe could experience stormier winters, while the Sahel in Africa and the monsoon regions of Asia would most likely get less rain.

Something to consider. London is about 4 degrees south of Moscow's lattitude, not quite 300 miles. I shudder to think of what winters would be like in Britain without the warming effects of the current Atlantic currents.

Not all scientists trust the research. From The Guardian:

Prof Niklas Boers, from the Potsdam Institute for Climate Impact Research in Germany, revealed the early warning signs of Amoc collapse in 2021. “The results of the new study sound alarming but if the uncertainties in the heavily oversimplified model [of the tipping point] and in the underlying [sea temperature] data are included, then it becomes clear that these uncertainties are too large to make any reliable estimate of the time of tipping.”

Prof David Thornalley, at University College London, UK, agreed the study had large caveats and unknowns and said further research was essential: “But if the statistics are robust and a relevant way to describe how the actual Amoc behaves, then this is a very concerning result.”

It's probably too early to say whether the study is accurate, but the fact that there's enough evidence to lead researchers to their rather scary conclusion is concerning and should strengthen the case for more rapid reduction in carbon emissions.