10C Worst-Case Warming Within Our Reach, And Within Just A Few Hundred Years

Scientists just completed one of the most comprehensive investigations of Earth’s climate history—and the findings aren’t favorable. They found that the planet could eventually warm to levels it hasn’t reached in at least 34 million years.

The researchers, led by Thomas Westerhold of the University of Bremen in Germany, constructed datasets using chemical analyses of ancient sediments, drilled from the bottom of the ocean. These sediments, some of which are 66 million years old, are filled with the preserved shells of tiny organisms that can tell scientists about the temperature and chemical composition of the ocean when they were formed.

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In the hottest phases, more than 50 million years ago, temperatures on Earth were more than 10 degrees Celsius hotter than they are today. But it’s important to note that it took the planet thousands or even millions of years to reach these levels—and that was long before humans ever walked the Earth. That’s in stark contrast to the kind of climate change that human activity is driving today.

For several million years now, the world has been in an icehouse state. But that’s quickly changing. If human societies do nothing to curb their greenhouse gas emissions, in just a few centuries the Earth could once again reach a temperature threshold not seen for at least 34 million years. Before the industrial era, such a magnitude of warming would have taken thousands of years to occur, at least. “If you look at the worst-case scenario [by 2300], the change in mean global temperature is larger than most of the natural variability going back over the last 66 million years related to changes in the Earth’s orbit,” said Jim Zachos, a paleoclimatologist at the University of California, Santa Cruz, and a co-author of the new study, which was published Thursday in the journal Science.

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https://www.scientificamerican.com/article/earth-hasnt-warmed-this-fast-in-tens-of-millions-of-years/