There was a time when the earth had no drizzle at all

You thought it rains hard now? It could be much worse.

Right now we are already experiencing the dramatic impact that just a small global temperature rise can have on our planet’s climate. Now imagine an Earth twice as warm as it is today. The Earth has likely experienced such scorching temperatures at various times in the distant past. And it may do so again in hundreds of millions of years, as the sun gets brighter and brighter. But what are the consequences of such rising temperatures on precipitation?

Greenhouse period

At the moment we actually know very little about how the atmosphere and climate behaved during so-called ‘greenhouse periods’. And yet that is quite interesting. Thus, the current research not only sheds light on Earth’s distant past or future, but may also help to better understand the climates on exoplanets orbiting distant stars.

Atmospheric model

In the study, the researchers built an atmospheric model. In this model, they then raised the temperature of the Earth’s sea surface to a sweltering 50 degrees Celsius. They did this by adding CO2 to the atmosphere on the one hand and increasing the sun’s brightness by about 10 percent on the other. Then they studied its consequences.

Surprising

The researchers discover that surprising things happen in the atmosphere at such temperatures. When the air near the surface becomes extremely hot, absorption of sunlight by atmospheric water vapor heats the air above the surface. This creates a kind of barrier that prevents clouds from rising to the upper parts of the atmosphere and forming rain clouds there. Instead, all that evaporation gets trapped in the nearby surface atmosphere. At the same time, clouds are forming in the upper atmospheres – above the aforementioned barrier – as heat leaks into space. The rain that forms in these clouds then evaporates before it reaches the surface.

Precipitation

What does this mean for precipitation? In particular, that drizzle was not an option. Because if anything breaks through the barrier, and the heat and humidity from the surface penetrates into the cool upper atmosphere, it will cause massive downpours.

Drought and downpours

The bottom line is that when global temperatures were high, this extreme heat may have led to major droughts. These dry spells were then followed by massive downpours. And then it rained and poured. For example, these extreme rain showers stretched for hundreds of kilometers. In just a matter of hours, as much as 30 centimeters of rain came down.

Incidentally, this periodic cycle of floods is a new and completely unexpected atmospheric condition. “If you look at the tropics now, it’s always raining somewhere,” said researcher Jacob Seeley. “But we found that in extremely hot climates it can be bone dry for several days at a time. Then, suddenly, a huge downpour would break out. Then it is quiet again for a few days before the pattern repeats itself.”

“Our research shows that there are still many surprises hidden in the climate system,” says Seeley. “While a doubling of seawater temperatures is much higher than predicted, the atmospheric model does give us an idea of ​​what the Earth is capable of.”