Earth could have experienced massive rainstorms in the distant past that rained more than a foot (30 centimeters) in a matter of hours.
Researchers have created models of several periods of extreme heat on the planet. These times were around 320 Kelvin (47 degrees Celsius). They believe that there would have been rapid deluges of rainfall following cycles of dryness.
According to the researchers behind the study, this cycle represents a "new and totally unexpected atmospheric state". It can help us understand the past and future Earth. Additionally, it can inform our observations of exoplanets that are not part of our Solar System.
Jacob Seeley, a climate scientist at Harvard University in Massachusetts, says that if you look at large areas of the deep tropical tropics today it would rain somewhere.
"But, we discovered that in very warm climates, it could be several days without rain over a large part of the ocean. Then suddenly, a huge rainstorm would burst across the entire domain, dropping a lot of rain. It would then be quiet for a few days, and then it would repeat.
Researchers created a series simulations that increased the temperature by up to 130 degrees Fahrenheit (54° Celsius), which is higher than the current Earth's temperature. The researchers tested both increases in atmospheric CO2 (up to 64x current levels) as well as increases in the Sun’s brightness.
Temperature increases of this magnitude can create an "inhibition layers", which are layers near the surface that are caused by heated atmospheric water vapour. These inhibit convective clouds and prevent them from rising to form rain clouds. This layer keeps evaporation at the surface.
Clouds form in the upper atmosphere as heat is lost to space. Because of the heat, rain from these clouds evaporates before reaching the surface. The excess heat causes water to continue to build. The inhibition layer is eventually broken, and this causes a deluge that can last for hours.
Seeley says, "It's almost like charging a huge battery." This barrier separates the cooling from the heating and evaporation at the surface.
"If anything can break through that barrier, and allow the heat and humidity of the surface to penetrate the cooler upper atmosphere, it will cause a huge rainstorm."
Researchers found that they could observe more rain in six hours than what tropical cyclones drop in the US over several days. This is a lot of water. After it has been released, the "atmospheric batteries" recharge and the cycle continues.
Researchers report that the hothouse convection observed in this study is comparable in some respects with what can be seen in the Great Plains of America, but on an even larger scale.
No one is forecasting such drastic rises in Earth's temperature, despite the dire climate crisis. The research is vital in understanding the climate of Earth and mapping out the future of our planet over millions of years, as the Sun continues its brightening.
"This study revealed new physics in a climate which is just a little different from the present-day Earth, from a planetary perspective." Robin Wordsworth from Harvard University is an environmental scientist.
"It raises new questions about climate evolution on Earth and other planets, which we'll be working through for many more years."
Nature published the research.
