climate change: extreme rainfall

Climate modeling has shown that during periods of extreme warming, the Earth has experienced rainfall of incredible magnitude and strength.

Current climate change threatens to raise the temperature of the planet by several degrees. However, in the past, it has also gone through periods of more serious warming, sometimes warming a couple of dozen degrees above current levels. At such temperatures, the ice caps near the poles melted completely, and the living world faced dangerous challenges. However, the behavior of the atmosphere under conditions of such a hot Earth is poorly understood.

Therefore, Jacob Seeley (Jacob Seeley) and Robin Wordsworth (Robin Wordsworth) from Harvard University have conducted computer simulations and found that during the hottest climatic eras droughts were replaced by rains of incredible intensity, which covered many hundreds of kilometers, shedding tens of centimeters of rain in a few hours. They write about it in a paper published in the journal Nature.

Global Warming

«If you consider vast expanses of the tropics today, it’s bound to rain somewhere,» Jacob Seeley explained. — But we’ve shown that in extremely warm climates, whole days must go by without a drop of rain over a vast area over the ocean. Then suddenly a powerful downpour would unleash almost all over the region, pouring out incredible amounts of water. Then there was silence for a couple of days, and it would happen again.

Simulating an extreme climate change, the scientists introduced into the calculations an increased amount of atmospheric carbon dioxide (in some versions — 64 times the current amount) or an increase in the brightness of the Sun (up to 10 percent), which led to the heating of the planet to more than 50 degrees Celsius. It was under such conditions that a short-term cycle leading to the appearance of extreme downpours occurred.

Due to the intense evaporation of moisture from the surface of the planet, an «inhibiting layer» emerged over it, which prevented the rise of water to the height of the formation of rain clouds. Those clouds that formed higher up could rain, but this moisture evaporated before it could reach the ground and caused only cooling.

As a result, water accumulated in the air, and the temperature dropped to the point where clouds could appear in spite of the «inhibiting layer,» and all the accumulated moisture fell in a downpour. «It’s like charging a huge battery,» adds Jacob Seeley. Climatologists estimate that such rains could dump more than a foot (30 centimeters) of rain in a matter of hours.

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