The Earth’s climate has undergone some big changes, from global volcanism to planet-cooling ice ages and dramatic shifts in solar radiation. And yet life, for the last 3.7 billion years, has kept on beating.
Now, a study by Massecuites Institute of Technology (MIT)researchers in Science Advances confirms that the planet harbors a “stabilizing feedback” mechanism that acts over hundreds of thousands of years to pull the climate back from the brink, keeping global temperatures within a steady, habitable range.
Just how does it accomplish this? A likely mechanism is “silicate weathering” — a geological process by which the slow and steady weathering of silicate rocks involves chemical reactions that ultimately draw carbon dioxide out of the atmosphere and 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. The mechanism of silicate weathering could provide a geologically constant force in keeping carbon dioxide — and global temperatures — in check. But there’s never been direct evidence for the continual operation of such a feedback, until now.
The new findings are based on a study of paleoclimate data that record changes in average global temperatures over the last 66 million years. The MIT team applied a mathematical analysis to see whether the data revealed any patterns characteristic of stabilizing phenomena that reined in global temperatures on a geologic timescale.
They found that indeed there appears to be a consistent pattern in which the Earth’s temperature swings are dampened over timescales of hundreds of thousands of years.
The duration of this effect is like the timescales over which silicate weathering is predicted to act.
The results are the first to use actual data to confirm the existence of stabilizing feedback, the mechanism of which is likely silicate weathering. This stabilizing feedback would explain how the Earth has remained habitable through dramatic climate events in the geologic past.
The study is co-authored by Constantin Arnscheidt and Daniel Rothman, professor of geophysics at MIT.
“You have a planet whose climate was subjected to so many dramatic external changes. Why did life survive all this time? One argument is that we need some sort of stabilizing mechanism to keep temperatures suitable for life,” Arnscheidtsays. “But it’s never been demonstrated from data that such a mechanism has consistently controlled Earth’s climate. Now we have data going back 66 million years, with data points at most thousands of years apart.”
Using this approach, the team analyzed the history of average global temperatures over the last 66 million years, considering the entire period over different timescales, such as tens of thousands of years versus hundreds of thousands, to see whether any patterns of stabilizing feedback emerged within each timescale.
Without stabilizing feedback, fluctuations of global temperature should grow with timescale. But the team’s analysis revealed a regime in which fluctuations did not grow, implying that a stabilizing mechanism reigned in the climate before fluctuations grew too extreme. The timescale for this stabilizing effect — hundreds of thousands of years — coincides with what scientists predict for silicate weathering.
“There’s an idea that chance may have played a major role in determining why, after more than 3 billion years, life still exists,” Rothman offers.
In other words, as the Earth’s temperatures fluctuate over longer stretches, these fluctuations may just happen to be small enough in the geologic sense, to be within a range that a stabilizing feedback, such as silicate weathering, could periodically keep the climate in check, and more to the point, within a habitable zone.
“There are two camps: Some say random chance is a good enough explanation, and others say there must be a stabilizing feedback,” Arnscheidt says. “We’re able to show, directly from data, that the answer is probably somewhere in between. In other words, there was some stabilization, but pure luck likely also played a role in keeping Earth continuously habitable.”
Research from the Massachusetts Institute of Technology (MIT) has found that the Earth is capable of regulating and stabilizing its temperature across vast timescales and even after dramatic changes in climate.
The Nov. 16 study published in Science Advances elaborated on the planet’s “stabilizing feedback system,” which has allowed the existence of diverse life-forms for the past 3.7 billion years or so. While this feedback has been assumed before, the study now serves as primary evidence for the existence of this system.
“You have a planet whose climate was subjected to so many dramatic external changes,” said MIT climate scientist and study co-author Arnscheidt. “Why did life survive all this time? One argument is that we need some sort of stabilizing mechanism to keep temperatures suitable for life. But it’s never been demonstrated from data that such a mechanism has consistently controlled Earth’s climate.”
Top o’ the morning!