MIT reveals the Earth's "self-rescue" mechanism, which takes hundreds of thousands of years at a time

Currently, climate change has become an “invisible killer” that threatens the world’s 8 billion people and the entire earth’s ecology.

However, in the longer history of the Earth, the Earth's climate has experienced more and more severe changes - from global volcanic eruptions to global cooling ice ages and drastic changes in solar radiation.

However, the pulse of life on Earth has been "beating" for the past 3.7 billion years. Why is this?

In a study, scientists Constantin Arnscheidt and Daniel Rothman from the Massachusetts Institute of Technology confirmed that the Earth has the ability to "resurrect from the dead" and can regulate its own temperature and save itself over hundreds of thousands of years.

That is, a "stabilizing feedback" mechanism exists on Earth that can pull the global climate back from the brink of collapse over hundreds of thousands of years, keeping the temperature within a stable, habitable range. This is the first time that scientists have used actual data to confirm the existence of a stabilizing feedback.

The related research paper, titled "Presence or absence of stabilizing Earth system feedbacks on different time scales", has been published in the scientific journal Science Advances.

(Source: Science Advances)

So how does the Earth slowly "save itself" over a cycle lasting hundreds of thousands of years? One possible mechanism is "silicate weathering."

It is reported that during the slow and steady weathering of silicate rocks, a chemical reaction occurs that absorbs carbon dioxide from the atmosphere and "traps" it in marine sediments and rocks.

**Early in previous studies, scientists have discovered signs that the Earth's carbon cycle has a climate-stabilizing effect: **Chemical analysis of ancient rocks shows that even when global temperatures fluctuate drastically, the carbon flux in and out of the Earth's surface environment remains relatively balanced; silicate weathering models predict that this process should have a certain stabilizing effect on the global climate; and the fact that the Earth has been habitable for such a long time suggests that there is some kind of built-in geological mechanism to cope with extreme temperature fluctuations.

“The planet’s climate has been subject to so many dramatic external changes. Why has life persisted? One view is that the Earth needs some kind of stabilizing mechanism to maintain a temperature suitable for life,” Arnscheidt said. “But there has never been data to show that this mechanism has always controlled the Earth’s climate.”

Arnscheidt and Rothman therefore analysed the history of global average temperatures over the past 66 million years, considering entire periods on different time scales (e.g. tens of thousands, hundreds of thousands of years) to see if the data reveal patterns characteristic of stabilising phenomena that control global temperatures over geological time scales. Without stabilising feedbacks, fluctuations in global temperature should grow over time scales.

“In a way, it’s like your car is accelerating down the street, and when you hit the brakes, the car slides for a long time before coming to a stop,” Rothman said. “There’s a timescale when the system returns to a stable state, and the frictional resistance or stabilizing feedback kicks in.”

Figure | Temperature fluctuations and feedback mechanisms. (Source: This paper)

However, the study revealed a mechanism of fluctuations but no growth, whereby the Earth's temperature fluctuations are controlled on a time scale of hundreds of thousands of years, which means that before the fluctuations grow to extremes, the global climate is indeed subject to a stabilizing mechanism. Moreover, the time scale of this stabilization (hundreds of thousands of years) is consistent with the time scale predicted by scientists for silicate weathering.

This stabilizing feedback could therefore explain how the Earth has remained stable and habitable during dramatic climate events in the geological past.

(Source: Pixabay)

Interestingly, Arnscheidt and Rothman found that the data showed no stable feedback on longer time scales . That is, on time scales longer than a million years, global temperatures did not seem to fall back repeatedly.

So what controls global temperatures on these longer time scales?

"One idea is that chance may have played a big role in determining why life still exists after more than 3 billion years ," Rothman said.

That is, as Earth's temperature fluctuates over longer periods of time, those fluctuations may just be small enough in geological terms to fall within a range where stable feedbacks, such as silicate weathering, can periodically control climate under a set of conditions.

“Some people would argue that random chance is a good enough explanation, others would insist that there must be a stabilizing feedback, and we find from the data that the answer is probably somewhere in between,” Arnscheidt said . In other words, in addition to Earth’s own stabilizing feedback, pure luck may also have played a role in keeping the planet continually habitable.

Arnscheidt said of the finding, "This is good news because we know that current global warming will eventually be offset by this stabilizing feedback; but this process will take hundreds of thousands of years, which is not fast enough to solve the climate problems we are facing today ."

Besides, will the Earth always be that lucky?

Reference Links:

https://www.science.org/doi/10.1126/sciadv.adc9241