Peter Brannen in The Guardian:
Many of us share some dim apprehension that the world is flying out of control, that the centre cannot hold. Raging wildfires, once-in-1,000-years storms and lethal heatwaves have become fixtures of the evening news – and all this after the planet has warmed by less than 1C above preindustrial temperatures. But here’s where it gets really scary.
If humanity burns through all its fossil fuel reserves, there is the potential to warm the planet by as much as 18C and raise sea levels by hundreds of feet. This is a warming spike of an even greater magnitude than that so far measured for the end-Permian mass extinction. If the worst-case scenarios come to pass, today’s modestly menacing ocean-climate system will seem quaint. Even warming to one-fourth of that amount would create a planet that would have nothing to do with the one on which humans evolved or on which civilisation has been built. The last time it was 4C warmer there was no ice at either pole and sea level was 80 metres higher than it is today.
I met University of New Hampshire paleoclimatologist Matthew Huber at a diner near his campus in Durham, New Hampshire. Huber has spent a sizable portion of his research career studying the hothouse of the early mammals and he thinks that in the coming centuries we might be heading back to the Eocene climate of 50 million years ago, when there were Alaskan palm trees and alligators splashed in the Arctic Circle.
“The modern world will be much more of a killing field,” he said. “Habitat fragmentation today will make it much more difficult to migrate. But if we limit it below 10C of warming, at least you don’t have widespread heat death.”
In 2010, Huber and his co-author, Steven Sherwood, published one of the most ominous science papers in recent memory, An Adaptability Limit to Climate Change Due to Heat Stress.
“Lizards will be fine, birds will be fine,” Huber said, noting that life has thrived in hotter climates than even the most catastrophic projections for anthropogenic global warming. This is one reason to suspect that the collapse of civilisation might come long before we reach a proper biological mass extinction.