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Earth regulates its own temperature over time, scientists say

Geological processes such as silicate weathering stabilized the Earth's temperature over millennia, scientists say, but such processes may not do much to mitigate current climate change issues.

(CN) — Since the early 1980s, scientists have believed that silicate weathering plays a major role in stabilizing Earth's surface temperature, but they could really only theorize as to what unknown factor kept the planet, and by extension everything on it, alive despite climate changes. In a study published Wednesday in Science Advances, scientists say they've confirmed that theory.

Daniel Rothman, professor of geophysics at MIT, and Constantin Arnscheidt, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences (EAPS), studied global temperature records compiled by other scientists, including records of the chemical composition of ancient marine fossils and shells as well as preserved Antarctic ice cores. According to Arnscheidt, the team studied the history of average global temperatures going back 66 million years.

“We wanted to analyze datasets that span a wide time interval but also have a relatively high resolution,” Arnscheidt said via email. “A lot of effort has gone into understanding the record of global temperature evolution for the last 66 million years (the Cenozoic Era), and the data points are now at most a few thousand years apart.”

To identify any patterns of stabilizing feedback, Rothman said that the team analyzed the entire period over different timescales, such as tens of thousands of years versus hundreds of thousands.

“To some extent, it’s like your car is speeding down the street, and when you put on the brakes, you slide for a long time before you stop,” said Rothman. “There’s a timescale over which frictional resistance, or stabilizing feedback, kicks in, when the system returns to a steady state.”

Per the study, the team’s analysis implies that a stabilizing mechanism prevented global temperatures from fluctuating as time passed. Also, the hundreds of thousands of years timescale coincided with scientific predictions for silicate weathering — what the study described as a geological process that draws carbon dioxide out of the atmosphere and into ocean sediments to slowly and steadily weather silicate rocks, trapping the gas insde.

To Arnscheidt and Rothman’s perplexion, the data did not reveal any stabilizing feedback or recurring global temperature pull-back on timescales longer than a million years. The scientists theorized that as the Earth’s temperature fluctuated over longer stretches, these fluctuations were small enough on a geological level that stabilizing feedback, such as silicate weathering, could periodically keep the climate within a habitable zone.

Arnscheidt offered an additional theory – pure luck.

“Well, the simplest explanation is that there were no dominant stabilizing feedbacks in this timescale regime,” wrote Arnscheidt. “This has really interesting implications: For example, it suggests that random chance may have played a role in keeping Earth's temperature habitable on timescales of many millions of years."

Regardless of whether Earth remained habitable to the present day because of stabilizing feedback, Arnscheidt said that it may not mitigate current climate change issues.

“On the one hand, it’s good because we know that today’s global warming will eventually be canceled out through this stabilizing feedback,” said Arnscheidt. “But on the other hand, it will take hundreds of thousands of years to happen, so not fast enough to solve our present-day issues.”

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