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    Friday, September 22, 2023

    If jet or gulf streams collapse, we're in for it

    A woman throws away flood damaged rubbish July 19 in the center of Bad Neuenahr-Ahrweiler, Germany. (Bram Janssen/AP Photo)

    The weather disasters spanning the globe this summer − infernal fires in California and Greece, deadly floods from Germany to China, heat waves from Canada to Siberia − are really just nature's shots across our bow.

    That becomes clear if you absorb this week's report by the Intergovernmental Panel on Climate Change, the body of the United Nations that assesses the state of science on global warming. No matter what policies we adopt − and obviously we should aim for good ones - the weather will keep getting more catastrophic more often.

    Part of what makes the overall problem of climate change so psychologically daunting is that there's so much we know, but so much more that we know only partially, and even more that we have yet to understand at all.

    We know perfectly well, for example, how coal-fired power plants pump carbon dioxide into the air - bad. We only partially understand how the thawing permafrost could release enough methane on top of the greenhouse gases we've emitted to cause additional, sudden and terrifying spikes in warming - really bad. And we have yet to figure out exactly how all this would affect the earth system as a whole, and in particular the massive currents of air and water that have made the world a familiar habitat to us.

    One current of particular concern is the polar jet stream, a group of winds that whips at enormous speeds around the Arctic from west to east (owing to the earth's rotation) at a height of six-to-10 miles up in the atmosphere. Another is the Gulf Stream, a vast oceanic conveyor belt that makes warm water from the tropics flow northward on the surface until it cools and, around Iceland, sinks down and heads back south.

    One thing these streams have in common, with each other and the many other currents all around the world, is that they're caused by temperature differences between the hot tropics and the cold poles. Another thing they share is that, in their own ways, they protect or nurture us humans.

    The complex swirls of the jet streams tend to blow away pressure systems that could otherwise kill us on the ground with storms and floods and heat. If these streams blow less hard, or more weirdly, or not at all, those meteorological danger domes just hover in place without moving, until they discharge their payloads on us. Although the details aren't clear yet, scientists believe this partially explains why the floods in Germany, the heat waves in North America and forest fires in Greece and Turkey turned into such doozies.

    Changes in the Gulf Stream work more slowly but are just as consequential. It's already known that the current is at its weakest in a millennium. There are many reasons, including torrents of freshwater pouring in from melting ice and bloated rivers (freshwater is lighter than saltwater and prevents cooling water from sinking) and shrinking temperature differentials between south and north as the Artic heats up. A new study in Nature suggests that the whole Atlantic circulation and convection system may "collapse" altogether.

    Whether and when such a "tipping point" will be reached remains controversial among scientists. But if this is our destiny, the world will never be the same again. Europe would no longer be relatively mild, and the climate would change beyond recognition from eastern North America to Africa and India. The Atlantic − already under duress from from acidification, plastic, overfishing and more − may no longer be able to sustain the food chains we rely on.

    As a non-scientist and humanist, I feel humility and awe in the face of this multiplying research. Immodestly, we've already named the current geologic epoch after ourselves − the Anthropocene - because for the first time humans determine much of what happens on our planet.

    Increasingly, it feels to me like we're living out an ancient Greek tragedy. In our arrogance (hubris) we're interfering with every part of nature (phusis) until eventually it − playing the part of the gods in Aeschylus or Sophocles − takes its revenge (nemesis).

    Like the tragic figures of old, we're doomed to be blind until it's too late. We don't understand how things are connected; we don't appreciate how we're parts of a whole; we don't see how decisions taken here and now could one day stop the winds and halt the seas.

    Andreas Kluth is a columnist for Bloomberg Opinion. He was previously editor in chief of Handelsblatt Global and a writer for the Economist.

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