Earth can regulate its own temperature over millennia

The Earth's climate has undergone 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.

The famous Earthrise photograph taken by Apollo 8 during the crew’s first orbit around the Moon. Photo: NASA

Now, a study by MIT researchers 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 erosion of silicate rocks involves chemical reactions that ultimately draw carbon dioxide out of the atmosphere and into ocean sediments, where the carbon dioxide is incorporated into sedimentary 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 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 time scale.

They found that indeed there appears to be a consistent pattern in which the Earth's temperature swings are dampened over time scales of hundreds of thousands of years. The duration of this effect is like the time scales over which silicate weathering is predicted to act.

The results are the first to use actual data to confirm the existence of a 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.

"This study combines systems modeling with paleoceanographic data to explore variations in Earth's surface temperature over a range of time scales," says Dan McCorkle, a program director in NSF's Division of Ocean Sciences.

"The results provide a compelling confirmation of the linked roles of weathering reactions and ocean sedimentation as stabilizing influences on Earth's long-term surface temperature." (U.S. National Science Foundation)

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