September 28, 2022

Epochs of Extreme Heat: On Ancient Earth, It Never Rained but It Poured

By Harvard John A. Paulson School of Engineering and Applied Sciences
November 15, 2021

Extreme Heat Led to Episodic Deluges on Hothouse Earth
Today, we are experiencing the significant impacts that even a small boost in international temperatures can have on a planets climate. Now, imagine an Earth 20 to 30 degrees Fahrenheit hotter than today. Earth likely experienced these temperatures at different times in the distant past and will experience them once again hundreds of millions of years from now as the sun continues to lighten up.
Little is learnt about how the environment and environment acted throughout these so-called hothouse periods. In a brand-new study, scientists from Harvard University found that during these epochs of severe heat, Earth might have experienced cycles of dryness followed by enormous rainstorms numerous miles wide that could discard more than a foot of rain in a matter of hours.

” If you were to look at a big patch of the deep tropics today, its constantly drizzling someplace,” stated Jacob Seeley, a Postdoctoral Fellow in Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Department of Earth and Planetary Science at Harvard and very first author of the paper. “But we found that in incredibly warm environments, there could be several days without any rain anywhere over a substantial part of the ocean. Then, suddenly, an enormous rainstorm would erupt over nearly the whole domain, disposing a significant quantity of rain. Then it would be quiet for a number of days and repeat.”
” This episodic cycle of deluges is a totally unforeseen and brand-new atmospheric state,” said Robin Wordsworth, the Gordon McKay Professor of Environmental Science and Engineering at SEAS and senior author of the study.
The research not only clarifies Earths far-off past and distant future however might likewise help to comprehend the climates of exoplanets orbiting distant stars.
The research is published in Nature.
In an atmospheric design, Seeley and Wordsworth cranked up Earths sea surface temperature to a scalding 130 degrees Fahrenheit, either by including more CO2– about 64-times the amount presently in the environment– or by increasing the brightness of the sun by about 10 percent.
At those temperatures, unexpected things start taking place in the atmosphere. When the air near the surface becomes incredibly warm, absorption of sunlight by climatic water vapor heats up the air above the surface and forms whats referred to as an “inhibition layer”, a barrier that prevents convective clouds from rising into the upper environment and forming rain clouds.
Instead, all that evaporation gets stuck in the near-surface environment.
At the same time, clouds form in the upper atmosphere, above the inhibition layer, as heat is lost to area. The rain produced in those upper-level clouds vaporizes before reaching the surface, returning all that water to the system.
” This episodic cycle of deluges is a completely unforeseen and brand-new atmospheric state.”– Robin Wordsworth, Gordon McKay Professor of Environmental Science and Engineering
” Its like charging an enormous battery,” stated Seeley. “You have a ton of cooling high in the environment and a lot of evaporation and heating near the surface, separated by this barrier. If something can break through that barrier and enable the surface heat and humidity to break into the cool upper atmosphere, its going to cause a massive rainstorm.”
Thats precisely what takes place. After numerous days, the evaporative cooling from the upper atmospheres rainstorms erodes the barrier, triggering an hours-long deluge. In one simulation, the researchers observed more rainfall in a six-hour duration than some tropical cyclones drop in the U.S. throughout a number of days.
After the storm, the clouds dissipate, and rainfall stops for several days as the atmospheric battery charges and the cycle continues.
” Our research study goes to show that there are still a lot of surprises in the environment system,” stated Seeley. “Although a 30-degree boost in sea surface area temperature levels is way more than is being predicted for human-caused climate modification, pressing atmospheric designs into unfamiliar area can expose glances of what the Earth is capable of.”
” This study has exposed abundant new physics in a climate that is only a little bit various from present-day Earth from a planetary perspective.” stated Wordsworth. “It raises big new questions about the environment development of Earth and other worlds that were going to be working through for numerous years to come.”
Reference: “Episodic deluges in simulated hothouse environments” by Jacob T. Seeley and Robin D. Wordsworth, 3 November 2021, Nature.DOI: 10.1038/ s41586-021-03919-z.

Now, envision an Earth 20 to 30 degrees Fahrenheit hotter than today. Earth likely experienced these temperature levels at different times in the far-off past and will experience them again hundreds of millions of years from now as the sun continues to brighten.
” If you were to look at a large patch of the deep tropics today, its always drizzling someplace,” said Jacob Seeley, a Postdoctoral Fellow in Environmental Science and Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and the Department of Earth and Planetary Science at Harvard and very first author of the paper. If something can break through that barrier and allow the surface heat and humidity to break into the cool upper environment, its going to cause a huge rainstorm.”
“It raises huge brand-new questions about the climate development of Earth and other worlds that were going to be working through for numerous years to come.”

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