Earth’s climate has undergone major changes, from global volcanism to planet-cooling ice ages and drastic changes in solar radiation. Yet for the past 3.7 billion years, life has continued to struggle. A study now led by researchers at the Massachusetts Institute of Technology Science AdvancesIt confirms that there is a “stabilizing feedback” mechanism operating on the planet for hundreds of thousands of years to bring the climate back from end to end and keep global temperatures within a stable, habitable range.
How is this achieved? The likely mechanism is “silicate weathering,” a geological process in which the slow and regular weathering of silicate rocks involves chemical reactions that eventually drive atmospheric carbon dioxide into ocean sediments and trap the gas in the rocks.
Scientists have long suspected that silicate weathering plays an important role in regulating Earth’s carbon cycle. The silicate weathering mechanism can provide a geologically stable force to keep carbon dioxide and global temperature in check. But until now, there has been no direct evidence that such feedback works consistently.
The new discoveries are based on an examination of paleoclimatic data that records changes in average global temperatures over the past 66 million years. The MIT team applied mathematical analysis to see if the data revealed patterns unique to the stabilization phenomenon that keeps global temperatures on geological time scales.
They discovered that there is a consistent pattern in which Earth’s temperature fluctuations weaken over hundreds of thousands of years. The duration of this effect is similar to the time scales on which the effect of silicate weathering is estimated. The results are the first to use real-world data to support the existence of a stabilizing feedback mechanism likely to be silicate weathering. This stabilizing feedback could 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 offset by this stabilizing feedback,” says Konstantin Arnscheidt, a graduate student in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “But on the other hand, it would take hundreds of thousands of years, so it’s not fast enough to solve today’s problems.”
Co-authors of the study are Arnscheidt and Daniel Rothman, professor of geophysics at the Massachusetts Institute of Technology.
Data stability
Scientists have seen hints of a climate stabilizing effect in Earth’s carbon cycle before: Chemical analysis of ancient rocks has shown that carbon flux into and out of Earth’s environment remains relatively balanced despite dramatic fluctuations in global temperature. Additionally, silicate weathering models predict that the process should have some stabilizing effect on the global climate. And finally, the long-term habitability of the Earth points to a certain natural geological justification of extreme temperature fluctuations.
“You have a planet whose climate has undergone many dramatic external changes. Why has life lasted so long? One argument is that we need some kind of stabilization mechanism to maintain a habitable temperature,” says Arnscheidt. not proven.”
Arnscheidt and Rothman sought to confirm whether compensatory feedback was really at work by looking at data on global temperature fluctuations throughout geological history. They studied a set of global temperature records collected by other scientists, starting with preserved Antarctic ice cores, as well as the chemical composition of ancient marine fossils and shells.
“All of this research is only possible because significant progress has been made in improving the resolution of these deep-sea temperature records,” Arnscheidt said. “We currently have 66 million years of data, with data varying by thousands of years at most.”
speed to stop
The team applied the mathematical theory of stochastic differential equations, which is widely used to detect patterns in widely fluctuating datasets, to the data.
“We found that this theory makes predictions about what you would expect the Earth’s temperature history to look like if there were feedback that worked on certain time scales,” Arnscheidt said.
Using this approach, the team analyzed the history of average global temperatures over the past 66 million years and looked over the entire period at different time scales, such as tens of thousands to hundreds of thousands of years, to see if any compensatory feedback patterns emerged. always in scale. scale.
“It’s kind of like your car accelerating on the street, and when you brake, you’re skidding for a long time before you stop,” Rothman says. “There is a time scale on which frictional resistance or compensatory feedback kicks in when the system returns to a steady state.”
Without stabilizing feedback, fluctuations in global temperature should increase over time. But the team’s analysis found a regime in which emissions did not increase, implying that a stabilization mechanism prevailed in the climate before emissions became too extreme. The timescale of this stabilization effect—hundreds of thousands of years—matches scientists’ estimates for silicate weathering.
Interestingly, Arnscheidt and Rothman discovered that at longer time scales the data did not show any compensatory feedback. That is, there do not appear to be any repetitive declines in global temperatures on time scales greater than one million years. So what kept global temperatures low over these long periods of time?
“There’s an idea that chance may have played an important role in determining why life still exists after more than 3 billion years,” says Rothman.
In other words, as Earth’s temperature fluctuates over longer periods of time, these fluctuations may be small enough in geological terms to be within limits for a stabilizing feedback such as silicate weathering to keep the climate periodically in check and at most. Residential area.
“There are two camps: one says random chance is a good enough explanation, and the other says it has to be a stabilizing feedback,” says Arnscheidt. “We can show directly from the data that the answer is probably somewhere in the middle. In other words, there has been some stability, but sheer luck probably also played a role in keeping Earth permanently habitable.” Source
Source: Port Altele
