Extreme heat led to storms hundreds of miles wide on ancient Earth, say scientists

The Earth is likely to have experienced temperatures in the distant past 20 to 30 degrees Fahrenheit hotter than today, bringing storms hundreds of miles wide that could dump more than a foot of rain in a matter of hours, scientists say.

And there is a high chance the planet will experience them again hundreds of millions of years from now as the sun continues to brighten, according to a study.

Researchers from Harvard University who created atmospheric models found that during epochs of extreme heat, known as “hothouse periods”, Earth may have experienced cycles of dryness followed by massive rainstorms.

The scientists “cranked up” Earth’s sea surface temperature to 130F (54C), either by adding more carbon dioxide — about 64 times the amount now in the atmosphere — or by increasing the brightness of the sun by about 10 percent.

There were various points in Earth’s history where this could have happened, including a few billion years ago, thousands of million years ago and hundreds of million years ago.

Jacob Seeley, first author of the paper, said: “We found that in extremely warm climates, there could be multiple days with no rain anywhere over a huge part of the ocean.

“Then, suddenly, a massive rainstorm would erupt over almost the entire domain, dumping a tremendous amount of rain. Then it would be quiet for a couple of days and repeat.”

Robin Wordsworth, senior author of the study, published in Nature, added: “This episodic cycle of deluges is a new and completely unexpected atmospheric state.”

The experts say their research is not related to human-caused climate change, but it does shed light on Earth’s distant past and far-flung future.

In addition, it may also help to understand the climates of exoplanets - those outside the solar system - orbiting distant stars.

At temperatures of 20F or 30F above those today, an “inhibition layer” prevents convective clouds from rising into the upper atmosphere and forming rain clouds.

At the same time, other clouds form in the upper atmosphere, from which rain evaporates, returning all the water to the system. After several days, it erodes the barrier, triggering an hours-long deluge.

In one simulation, the researchers observed more rainfall in a six-hour period than some tropical cyclones drop in the US across several days.

“Although a 30-degree increase in sea surface temperatures is way more than is being predicted for human-caused climate change, pushing atmospheric models into unfamiliar territory can reveal glimpses of what the Earth is capable of,” said Seeley.