In a new paper published in Geophysical Research Letters, scientists analyzed more than twenty years’ worth of data on lake surface temperatures from 78 lakes around the world. Each lake was large enough to have had multiple samples taken from different locations. The team wanted to understand how often lake heat waves occur and then how much anthropogenic climate change has altered that occurrence rate. And the news isn’t good, to no one’s surprise.

Severe lake heat waves are now more than twice as likely to happen than they were in pre-industrial times. And those heat waves change a lake’s water conditions, causing stress for plants and animals, possibly leading to algae blooms, and just generally creating water quality problems. Lead author R. Iestyn Woolway, a climate scientist at Bangor University in Wales, explains: What really stood out was the magnitude of human contribution: Most of the severe lake heat waves we looked at had a significant anthropogenic imprint. There’s no escape for aquatic organisms when they are exposed to these extreme temperatures.

And that ‘twice as likely’ occurrence rate is what’s going on now. If we reach the 1.5 degrees Celsius of global warming laid out as a best-case scenario in the Paris Agreement, the lake heat waves are three times more likely. And if the temperature change is more on the order of 3 degrees Celsius, which is where we’re headed without a larger reduction in greenhouse gas emissions, those heat waves become 25 times more likely.

All of this is to say that global leadership needs to come together and find ways to prevent the worst-case outcome from happening, or we’re going to see a severe change in lake chemistry and depth as the Earth’s temperatures continue to climb.

More Information

AGU press release

“Severe Lake Heatwaves Attributable to Human-Induced Global Warming,” R. Iestyn Woolway, Clément Albergel, Thomas L. Frölicher, and Marjorie Perroud, 2022 February 24, Geophysical Research Letters