By Becky Oskin
Global cooling caused by some historic volcanic eruptions wasn’t as extreme as climate scientists recently thought, according to newly revised ice core records from Antarctica.
Volcanic eruptions blast sulfur-dioxide gas into the stratosphere, where it turns into tiny particles called sulfate aerosols that reflect the sun’s energy and cool the Earth. Snow falling in Antarctica records the levels of sulfate in the air at the time, and it eventually becomes ice drilled by researchers in long, tubular cores.
Researchers have measured sulfate concentrations in 26 ice cores from 19 different locations in Antarctica that cover the last 2,000 years of Earth’s history — the best record yet, the researchers said. The team synchronized the sulfate records with ice cores from Greenland, to determine if the eruptions had a truly global effect.
Along with finding previously unknown volcanic eruptions in the ice cores from before A.D. 500, the researchers discovered that some historic eruptions weren’t as hard on the planet as earlier climate models suggested.
Sorting out these signals helps improve climate models, said Michael Sigl, a climate scientist at the Desert Research Institute in Reno, Nevada, and lead author of the study, published July 6 in the journal Nature Climate Change.
The team identified 116 volcanic eruptions in the ice cores from the nearly 20 sites covering the past 2,000 years, including historic events such as Tambora in 1815, Kuwae in 1458 and Samalas (or Mount Rinjani) in 1257. Not all of these 116 eruptions are recorded in Greenland’s ice cores, but for their next project, the researchers are planning to assess sulfate levels in the Greenland cores.
“I think there will be more tropical eruptions there than we can detect at the moment,” Sigl said.