Science

Earth can regulate its own temperature for millennia, new study reveals

Earth can regulate its own temperature for millennia, new study reveals

Earth can regulate its own temperature for millennia, new study reveals

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Earth’s climate has undergone some major changes, from global volcanism to planet-cooling ice ages and dramatic changes in solar radiation. And yet, for the past 3.7 billion years, life has continued to tick.


Now, a study by MIT researchers at Science Advances confirms that the planet has a “stabilizing feedback” mechanism that operates over hundreds of thousands of years to pull the climate back from the brink, keeping global temperatures within a permanent habitable range.

Just how does it accomplish that? The likely mechanism is “silicate weathering” – a geological process involving the slow and steady weathering of silicate rocks chemical reactions which eventually draw carbon dioxide from the atmosphere into ocean sediments, trapping the gas in rocks.

Scientists have long suspected that silicate weathering plays a major role in regulating the Earth’s carbon cycle. A silicate weathering mechanism could provide a geologically constant maintenance force carbon dioxide—and global temperatures—under control. But there has never been direct evidence for the continuous action of such feedback until now.

The new findings are based on the study of paleoclimate data that record changes in average global temperatures over the past 66 million years. The MIT team reported a mathematical analysis to see if the data revealed any patterns characteristic of stabilizing phenomena that have restrained global temperatures on geological time scales.

They found that there really is a consistent pattern to where the Earth is temperature the oscillations are dampened over time scales of hundreds of thousands of years. The duration of this effect is similar to the time frames in which silicate weathering is predicted to occur.

The results are the first to use real data to confirm the existence of stabilizing feedback, the mechanism of which is likely to be silicate wear. This stabilizing feedback would explain how Earth remained habitable through dramatic climatic events in the geological past.

“On the one hand, that’s good because we know that today’s global warming will eventually be reversed through this stabilizing feedback,” says Constantin Arnscheidt, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “But on the other hand, it will take hundreds of thousands of years for that to happen, so not fast enough to solve our problems today.”

The study was co-authored by Arnscheidt and Daniel Rothman, professor of geophysics at MIT.

Data stability

Scientists have previously seen hints of a climate-stabilizing effect on Earth’s carbon cycle: Chemical analyzes of ancient rocks have shown that the flow of carbon into and out of Earth’s surface environment has remained relatively balanced, even through dramatic changes in global temperature. Furthermore, silicate weathering models predict that the process should have some stabilizing effect on the global climate. And finally, the fact of Earth’s permanent habitability points to some inherent geological check on extreme temperature changes.

“You have a planet whose climate has been subjected to such dramatic external changes. Why has life persisted all this time? One argument is that we need some kind of stabilization mechanism to maintain temperatures suitable for life,” says Arnscheidt. “But it has never been shown from the data that such a mechanism has consistently controlled Earth’s climate.”

Arnscheidt and Rothman tried to confirm whether the stabilizing feedback was indeed at work by looking at data on global temperature fluctuations throughout geologic history. They worked with a range of global temperature records compiled by other scientists, from the chemical composition of ancient marine fossils and shells, as well as preserved Antarctic ice cores.

“This entire study is only possible because there have been great advances in improving the resolution of these deep-sea temperature records,” notes Arnscheidt. “We now have data going back 66 million years, with data points thousands of years apart at most.”

Fast speed to a stop

The team applied the mathematical theory of stochastic differential equations, which is commonly used to detect patterns in widely fluctuating data sets, to the data.

“We realized that this theory makes predictions about what you would expect Earth’s temperature history to look like if there were feedbacks operating at certain timescales,” explains Arnscheidt.

Using this approach, the team analyzed the history of average global temperatures over the past 66 million years, considering the entire period on different timescales, such as tens of thousands of years versus hundreds of thousands, to see if any patterns of stabilizing feedback had emerged within each time frame.

“To some extent, it’s like your car is speeding down the street, and when you hit the brakes, you’re skidding for a long time before you stop,” Rothman says. “There is a time frame where frictional resistance, or stabilizing feedback, kicks in when the system returns to a steady state.”

Without stabilizing feedbacks, global temperature fluctuations should increase with time. But the team’s analysis revealed a regime in which fluctuations did not increase, implying that a stabilizing mechanism prevailed in the climate before fluctuations became too extreme. The time frame for this stabilizing effect—hundreds of thousands of years—matches what scientists predict for silicate weathering.

Interestingly, Arnscheidt and Rothman found that at longer timescales the data did not reveal any stabilizing feedback. That is, there appears to be no repeated retreat in global temperatures over timescales longer than a million years. On these longer timescales, what then kept global temperatures in check?

“There is an idea that chance may have played a major role in determining why, after more than 3 billion years, life still exists,” says Rothman.

In other words, as Earth’s temperatures fluctuate over longer timescales, these fluctuations may be small enough, in geological terms, to be within the range that a stabilizing feedback such as silicate weathering could occasionally keep the climate in check, and more precisely, within habitable zones.

“There are two camps: some say random chance is a good enough explanation, and others say there must be stabilization feedback,” says Arnscheidt. “We’re able to show, directly from the data, that the answer is probably somewhere in between. In other words, there was some stabilization, but sheer luck probably also played a role in keeping the Earth in a constant state of habitability.”

More information:
Constantin Arnscheidt, Presence or Absence of Earth System Stabilizing Feedbacks at Different Timescales, Science Advances (2022). DOI: 10.1126/sciadv.adc9241

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation, and teaching.

Citation: Earth can regulate its own temperature over millennia, new study finds (2022, November 16) Retrieved November 16, 2022 from https://phys.org/news/2022-11-earth-temperature-millennia.html

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