The World's a Jungle Again. Would Doldrums Blow the Global Air?

From 56 to 34 million years ago, Earth was so warm that we have found evidence of jungle plants inside the Arctic Circle. Nowadays, jungles are confined in or near the equator, and those latitudes are dominated by only one type of wind--the doldrums.

The doldrums is a colloquial expression derived from historical maritime usage, which refers to those parts of the Atlantic Ocean and the Pacific Ocean affected by a low-pressure area around the equator where the prevailing winds are calm. The doldrums are also noted for calm periods when the winds disappear altogether, trapping sailing ships for periods of days or weeks...Since this zone is where two trade winds meet, it is also called the Intertropical Convergence Zone. They roughly lie between latitudes 5° north and south.

So what formed this calm air?

In maritime usage, the low pressure characteristics of the doldrums are caused by the expanding atmosphere due to heating at the equator, which makes the air rise and travel north and south high in the atmosphere, until it subsides again in the horse latitudes. Some of that air returns to the doldrums through the trade winds. This process can lead to light or variable winds and more severe weather, in the form of squalls, thunderstorms, and hurricanes. The doldrums are also noted for calm periods when the winds disappear altogether, trapping sail-powered boats for periods of days or weeks.

In an alternate 21st century, Earth is as hot as it was during the Eocene, turning, for example, the frozen continent of Antarctica into the southernmost jungle, replacing penguins and skuas with grapes, figs, palms and citrus fruits. With such a hotter climate, would the oceans of the southern hemisphere still have the westerlies strong enough to be named Roaring Forties, Furious Fifties and Screaming Sixties? Or would those winds be demoted to doldrums?

posted over 6 years ago

JohnWDailey‭

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