Global heating – “best case” scenario is a scary rise of two and a half degrees

How Hot Will the Future Feel? New Yorker, 29 July 20, By Bill McKibben

Even among the grim daily toll of pandemic deaths and job losses, the most fateful numbers in the news last week probably came from a huge study carried out by a team of scientists at the World Climate Research Programme. It wove together the warming that we’ve observed so far, the latest understanding of feedback effects from clouds and other systems, and the record of the climate in the deep past to conclude that doubling the amount of carbon in the atmosphere (which, at current rates, will occur toward the middle of the century) will raise the average surface temperature on Earth between two and a half and four degrees Celsius

This is the first significant narrowing of that range in decades—ever since the nineteen-eighties, we’ve been saying one and a half to four and a half degrees. Now, though, researchers are essentially ruling out the bottom end of the range: two and a half degrees, now essentially the best-case scenario, is an enormous number. Dealing with the volume and complexity of data “was such a long and painful process,” one researcher, Kate Marvel, at nasa’s Goddard Institute, said. James Hansen, the former Goddard chief and the world’s premier climate scientist, said, “It is an impressive, comprehensive study, and I am not just saying that because I agree with the result. Whoever shepherded this deserves our gratitude.”

Indeed, they do. But, in truth, the numbers—what we might call pure climatology—can tell us only so much. What will haunt our future are two other variables, both of which are even harder to calculate. The first is: How much damage will that extra heat wreak? So far, scientists—who tend to be conservative in their forecasts—have under-predicted everything from coral die-off to Arctic ice melt. The past week, during which the Atlantic-hurricane alphabet hit “H” earlier in the season than ever before, provided more reminders that even the one degree Celsius that the temperature has already risen is an awful lot. In China, record rains were powering remarkably dangerous flooding along the Yangtze River—by last weekend, people were beginning to raise fears for the Three Gorges Dam, the largest structure of its kind in the world.

But, again, the level of damage that comes from rising temperatures—let’s call it applied climatology—is not as telling, ultimately, as our collective ability to respond to that damage. The brittleness of political systems in the face of change on this scale is even scarier than the brittleness of dams. The Times Magazine offered a remarkable glimpse into such a possibility this week, with a long examination of climate migration—present and future—from Central America. As more and more people find themselves in zones too hot to support life, they will move, and, as we already know, those movements provoke both compassion and demagoguery. “The best outcome requires not only good will and the careful management of turbulent political forces; without preparation and planning, the sweeping scale of change could prove wildly destabilizing,” Abrahm Lustgarten writes. “The United Nations and others warn that in the worst case, the governments of the nations most affected by climate change could topple as whole regions devolve into war.”

The pandemic shows us above all, I think, that twenty-first-century survival depends on an ability to handle chaos: that our political leaders, and our other institutions, have to devote themselves as never before to humane competence. And, as this summer’s racial reckoning should remind us, the pain that’s coming needs to be distributed far more fairly. We’re fast running out of margin. The capacity of political systems to respond to extreme stress can’t be predicted as numerically as the response of physical systems to extra carbon, but it will be measured, as with covid-19, in deaths. Just on a much larger scale…… https://www.newyorker.com/news/annals-of-a-warming-planet/how-hot-will-the-future-feel