VA Scientist Finds Another Reason for Extreme Weather

Feb 7, 2020

Scientists continue to study climate change – a warming planet caused by burning of  fossil fuels, but a professor at the University of Mary Washington has made another surprising discovery about extreme weather.

UMW Professor Pamela Grothe near Christmas Island
Credit Pamela Grothe

When trade winds blow across the Pacific Ocean, they push warm surface water east, causing cooler water from the deep to rise – bringing with it a rich supply of food for marine life, but during periods known as El Nino –  those winds shut down, causing a rise in surface temperatures – depriving wildlife of food and prompting changes in weather worldwide. 

“Even here in Virginia we might just have a wacky winter,”  says Pamela Grothe,  an assistant professor of earth and environmental sciences at the University of Mary Washington.

“Many places will get intense rainfall.  A lot of places go bone dry, and then they have problems with wildfires and crop failure.  Ocean temperatures heat up. Certain places it ends up shutting down the fisheries.”

Lately, she says El Nino events, which occur every 2-7 years, are more intense, but are these variations natural?  Have they occurred through history? Or could they be linked to the same industrial pollution that’s causing climate change?  Scientists have been tracking el ninos for less than a hundred years, but Grothe and her colleagues found a novel way to study patterns dating back thousands of years.

“We went to the Lion Islands in the central tropical Pacific.  They get hit the hardest during every type of El Nino event," she explains.  "The water gets warmer, it heats up, and the rainfall happens, so the water actually gets fresher as well, and corals are almost perfect recorders of surface temperature through their geochemistry. "

By studying fossilized coral, Grothe determined that extreme el ninos correspond closely with the time when people began burning coal and oil.

“The industrial record really sticks out like a sore thumb," she says. "If you look at the last twenty years – at the intensity of these swings -- they are stronger than any 20-year period from the pre-industrial record.”

And in the last 50 years, she discovered, el ninos were  25% stronger than in pre-industrial times.