Thousands of years ago, the Earth may have suffered from several gigantic floods that dumped more than a foot of rain in just a few hours. The researchers in the study, published in the journal Nature , remodeled the climate since the beginning of the planet , when the temperature would be around 47º C. They came to the conclusion that periods of drought were quickly replaced by major storms.
According to the team, this cycle is a “new and completely unexpected atmospheric state”. In addition to improving our understanding of Earth’s past and future, it can also improve our observations of planets outside our Solar System.
“If you look at a large portion of the tropics today, it’s always raining somewhere,” says climate scientist Jacob Seeley of Harvard University in Massachusetts.
“But we found that in extremely hot climates, there can be several days without rain anywhere along a large part of the ocean. Then, all of a sudden, a great storm breaks through most of the domain, pouring an enormous amount of rain. So everything is quiet for a few days and the cycle repeats”, he added.
To reach this conclusion, the researchers performed several temperature simulations. In one of them, scientists increased the temperature up to 130º C warmer than the Earth in that period.
These temperature jumps create an “inhibition layer” – a layer close to the Earth’s surface caused by heated atmospheric water vapor, which prevents convective clouds from rising and forming rain clouds .
At the same time, however, heat loss to space causes clouds to form in the upper atmosphere. The rain that these clouds cause evaporates even before reaching the surface, precisely because of the excessive heat. This evaporation ends up breaking the inhibition layer, triggering these floods that can last for hours.
“It’s like charging a huge battery,” says Seeley. “You have a ton of high cooling in the atmosphere and a ton of evaporation and heating near the surface, separated by this barrier.” “If something manages to break through that barrier and allow surface heat and moisture to invade the cold upper atmosphere, it will cause a huge storm,” he added.
In one of the simulations, researchers observed more rain in six hours than some tropical cyclones in the US produced in several days. In other words, it’s a lot of water falling from the sky.
“This study revealed rich new physics in a climate that is only slightly different from today’s Earth from a planetary perspective,” says environmental scientist Robin Wordsworth of Harvard University. “This raises big questions about the evolution of the Earth’s climate and other planets that we will work on for many years to come,” he concluded.