Not only that, but +4℃ is also when megafauna - any species over 45Kg (100lbs) - start to go extinct.
And that includes humans.
At that point, we’re looking at our global population free-fall cratering into the 1-2B range over 1-3 decades, at best. Worst-case is under 500M, with a full reversion back to the Bronze Age or earlier. And a continuing persistent (slower) decline down to a big fat zero.
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Not only that, but +4℃ is also when megafauna - any species over 45Kg (100lbs) - start to go extinct.
And that includes humans.
At that point, we’re looking at our global population free-fall cratering into the 1-2B range over 1-3 decades, at best. Worst-case is under 500M, with a full reversion back to the Bronze Age or earlier. And a continuing persistent (slower) decline down to a big fat zero.