Earth’s Largest Lake Evaporating Away As Temperatures Rise

The world’s largest inland body of water has been evaporating over the last couple of decades, with the sea level changing by several feet as surface temperatures have increased.

After a century of stable water levels, the Caspian Sea has been seriously fluctuating, researchers note in a study in the journal Geophysical Research Letters. In the last 20 years, it has dropped about 5 feet. And it may only get worse.

An increase in evaporation in the Caspian Sea “is closely related to surface temperature increases,” according to the authors. “With continued warming in the northern hemisphere, one can expect yearly accumulated evaporation rates over the Caspian Sea to continue increasing for the foreseeable future.”

That stable century before the sea’s fluctuations began spanned a time when the area was mostly “preindustrial,” the study explains. But the water dropped by about 10 feet between the 1930s and the 1970s, and then jumped up about 8 feet between the ‘70s and the ‘90s, before beginning another steady decline that has lasted until today.

During this steady decline, which saw the sea lose 3 inches of water each year from 1996 to 2015, the average surface temperature there also increased by almost 2 degrees Fahrenheit, the American Geophysical Union said in a statement about the research.

NASA astronaut Scott Kelly took this image of the Caspian Sea as the International Space Station orbited over it in 2015. Photo: Scott Kelly/NASA/JSC

“The real control that causes it to go up and down over long periods of time is really most likely the evaporation, which is almost completely dominated by temperature,” study co-author and geophysicist Clark Wilson said in the AGU report.

The Caspian Sea is Earth’s largest inland body of water, with a surface area of more than 140,000 square miles and stretching almost 750 miles from north to south. It borders Russia, Azerbaijan, Iran, Turkmenistan and Kazakhstan.

This body of water is enclosed and…

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