Currently — July 26, 2023: New paper concludes near-term collapse of key Atlantic Ocean circulation is now likely

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A new study, out Tuesday in the prestigious journal Nature Communications, has found that a key ocean current in the Atlantic is now expected to collapse by 2050, and as early as 2025.

The Atlantic Meridional Overturning Circulation (AMOC), the collapse of which was famously exaggerated in the movie The Day After Tomorrow, has collapsed many times in the past, most recently 12,000 years ago towards the end of the last ice age. Scientists think excessive meltwater coming from Greenland could be already pushing it toward another collapse, with the current now at its weakest in 1,600 years.

The most recent IPCC assessment concluded that a AMOC collapse is unlikely this century, and that global warming in excess of 8°C may be needed. A study published just seven years ago suggested just a 44% of a collapse by the year 2300, assuming Paris emissions reductions targets are met.

The new study uses a new method to estimate the effect of current and future emissions on the strength of the current and estimates a collapse by 2050, with a 95% confidence interval of 2025–2095. According to one of the researchers who helped collect some of the study’s data back in 2005, “it is mind boggling that almost 20 years later we are seriously looking at a collapse scenario in our lifetimes.”

German oceanographer Stefan Rahmstorf, whose past work has included study of the AMOC, has an extremely helpful 10 point overview of the study and how it has changed is view of what’s possible, including the possible likelihood of a near-term collapse.

The effects of a near-term collapse of the AMOC cannot be understated. The northward current provides warmth to the Gulf Stream that, if halted significantly, would sharply cool Northern Europe and worsen its shift towards drought while most of the rest of the world continues to warm. With the ocean no longer able to as effectively transfer heat between the Caribbean and Europe, Atlantic storms could greatly intensify in frequency and severity — according to research conducted by super scientist James Hansen.

Such consequences would be so dire that, according to the researchers, they should be “avoided at all costs”. In my person opinion — if there was ever a study that justifies world leaders declaring a climate emergency and winding down fossil fuels, it’s this one.

—Eric Holthaus