Welcome to the End of the ‘Human Climate Niche’

https://nymag.com/intelligencer/2020/05/welcome-to-the-end-of-the-human-climate-niche.html

By David Wallace-Wells
May 19, 2020

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The hurricane season has gotten going early this year, with a named tropical storm appearing before the official onset of hurricane season for the sixth year in a row

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In my book, The Uninhabitable Earth, I called the threat of simultaneous or successive disasters like these “climate cascades” — each making it harder to respond to the next. In California, Governor Gavin Newsom has worried that the states’ coronavirus prison furloughs, intended to reduce the risk of coronavirus spreading within prisons, may undermine its ability to fight wildfires this season, since a large share of the states’ firefighters are actually prisoners facing down flames for as little as $1 a day. Usually, they are outfitted for protection with N95 respirator masks. This season, those will almost certainly be in short supply as well. We tend to think of climate impacts as discrete threats: a wildfire, a hurricane, a drought. By the year 2100, it’s possible that parts of the planet will be hit by six climate-driven natural disasters at once. Wildfires tearing through communities cowering terrified by a rolling pandemic only counts as two.

This is what it means to be living already outside the “human niche.” The term comes from a landmark paper published late last month in the Proceedings of the National Academy of the Sciences, “Future of the Human Climate Niche.” What do the authors mean by it? In short, that the range of temperatures that make human flourishing possible is quite narrow, and that climate change promises to close that window — not entirely, but enough to meaningfully diminish how much of the planet can support prosperous, comfortable life.

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For millennia, human populations have resided in the same narrow part of the climatic envelope available on the globe, characterized by a major mode around ∼11 degrees Celsius to 15 [52F - 59F] degrees Celsius mean annual temperature. Supporting the fundamental nature of this temperature niche, current production of crops and livestock is largely limited to the same conditions, and the same optimum has been found for agricultural and nonagricultural economic output of countries through analyses of year-to-year variation.

Looking forward, they project that, even under a best-case emissions scenario, one that allows us to meet the goals of the Paris accords and pull up at about two degrees Celsius of warming, regions that are today home to 1.5 billion people would become, practically speaking, unlivable by 2070. Under those conditions, with no large-scale migration, roughly 13 percent of the global population in 2070 would be living in areas with a mean average temperature of 84 degrees Celsius — a mean temperature today found on less than one percent of the planet’s surface, mostly in the Sahara. [That's the average for the whole year, 24 hours a day.]

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