The early Earth suffered periodic bouts of floods . These storms were hundreds of kilometers wide and could dump a large amount of rain in a matter of hours and, according to a new study from Harvard University (USA), cycles of dryness followed by massive rain storms in the form of floods, they could repeat themselves hundreds of millions of years from now.
That’s how it is. Earth likely experienced these periods several times in its distant past and will experience them again hundreds of millions of years from now as the Sun continues to increase in brightness, say the researchers, who based their results on computer simulations.
“If you had to see a large part of the deep tropics today, it is always raining somewhere,” says Jacob Seeley, postdoctoral fellow in environmental sciences and engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS). and the Department of Earth and Planetary Sciences at Harvard. “But we found that in extremely hot climates, there could be several days without rain anywhere over a large part of the ocean. Then all of a sudden, a massive storm would break out over most of the domain, dumping an enormous amount of rain . Then it would be in Silence for a couple of days and I would repeat. “
“This episodic cycle of floods is a completely unexpected new atmospheric state,” clarifies Robin Wordsworth, Gordon McKay Professor of Environmental Science and Engineering at SEAS and lead author of the study reported in the journal Nature.
The research not only sheds light on Earth’s distant past and far future, it can also help understand the climates of exoplanets orbiting distant stars.
Computer simulation
In an atmospheric model, Seeley and Wordsworth increased the temperature of the Earth’s sea surface to 54 ° C, either by adding more CO2 to the atmosphere, approximately 64 times the current amount present in the atmosphere, or by increasing the brightness of the sun by about 10%.
What happens at these temperatures? When the air near the surface becomes extremely warm, the absorption of sunlight by atmospheric water vapor heats the air above the surface and forms what is known as an “inhibition layer,” a barrier that prevents convective clouds rise into the upper atmosphere and form rain clouds. That is, clouds form in the upper atmosphere whose rain evaporates before reaching the surface (returning all the water to the system).
After several days, evaporative cooling from upper atmosphere storms erodes the barrier, causing a deluge of several hours, as experienced several times in Earth’s history. After the storm, the clouds dissipate and the precipitation stops for several days while the atmospheric battery recharges and the cycle continues.
“Our research shows that there are still many surprises in the climate system ,” Seeley said.
“This study has revealed rich new physics in a climate that is only slightly different from Earth today from a planetary perspective. It raises big new questions about the climatic evolution of Earth and other planets that we will work on for many years to come.” Wordsworth concludes.
Referencia: Jacob T. Seeley, Robin D. Wordsworth. Episodic deluges in simulated hothouse climates. Nature, 2021; 599 (7883): 74 DOI: 10.1038/s41586-021-03919-z
