Is It So Bad if the World Gets a Little Hotter? Uh, Yeah.

If humanity burns through all its fossil fuel reserves, there is the potential to warm the planet by perhaps more than 10 degrees Celsius and raise sea levels by hundreds of feet.

This is a warming spike comparable in magnitude to that so far measured for the End-Permian mass extinction.

.. The last time it was 4 degrees warmer there was no ice at either pole and sea level was hundreds of feet higher than it is today.

.. in the coming centuries it’s not impossible that we might be headed back to the Eocene climate of 50 million years ago, when there were Alaskan palm trees and alligators splashed in the Arctic Circle.

.. “Lizards will be fine, birds will be fine,”

.. Huber says that, mass extinction or not, it’s our tenuous reliance on an aging and inadequate infrastructure—perhaps, most ominously, on power grids—coupled with the limits of human physiology that may well bring down our world.

.. “The problem is that humans can’t even handle a hot week today without the power grid failing on a regular basis,” he said, noting that the aging patchwork power grid in the United States is built with components that are allowed to languish for more than a century before being replaced.

.. By the year 2050, according to a 2014 MIT study, there will also be 5 billion people living in water-stressed areas.

.. “Thirty to fifty years from now, more or less, the water wars are going to start,” Huber said

.. “None of the economists are modeling what happens to a country’s GDP if 10 percent of the population is refugees sitting in refugee camps.

.. If people don’t have economic hope and they’re displaced, they tend to get mad and blow things up. It’s the kind of world in which the major institutions, including nations as a whole, have their existence threatened by mass migration.

.. Huber calculated their temperature thresholds using the so-called wet-bulb temperature, which basically measures how much you can cool off at a given temperature. If humidity is high, for instance, things like sweat and wind are less effective at cooling you down, and the wet-bulb temperature accounts for this.

.. Wet-bulb temperatures of 35 degrees Celsius or higher are lethal to humanity.

.. Above this limit, it is impossible for humans to dissipate the heat they generate indefinitely and they die of overheating in a matter of hours, no matter how hard they try to cool off.

.. 7 degrees Celsius of warming would begin to render large parts of the globe lethally hot to mammals.

.. truly huge swaths of the planet currently inhabited by humans would exceed 35 degrees Celsius wet-bulb temperatures and would have to be abandoned.

.. “In the near term—2050 or 2070—the Midwest United States is going to be one of the hardest hit,” said Huber. “There’s a plume of warm, moist air that heads up through the central interior of the US during just the right season, and man, is it hot and sticky. You just add a couple of degrees and it gets really hot and sticky.

.. the Hajj, which brings 2 million religious pilgrims to Mecca each year, will be a physically impossible religious obligation to fulfill due to the limits of heat stress in the region in just a few decades.

.. “You want to know how societies collapse?” Huber said.

“That’s how.”