Volcanic Eruptions Could be Slowing Down Global Warming

Volcanic eruptions that have been spewing over the last 14 years may be partially responsible for the cooling of Earth and slowing down the effects of global warming, a new study published in Nature Geoscience suggests.

Researchers attribute this helping hand to the 17 eruptions from 1998 to 2012 that pumped sulfur dioxide into Earth's upper atmosphere. The molecule formed liquid particles that reflected sunlight back to space rather than to the Earth's surface, moderating the larger-scale warming of the planet surface, the Los Angeles Times reported.

This discovery undermines the Intergovernmental Panel on Climate Change's (IPCC) computer models which predict a non-stop warming of our planet thanks to human activity.

The IPCC models assumed that volcanic aerosols would eventually fall to the ground and not remain in the atmosphere.

"That's not what happened in the real world," lead author of the study Benjamin D. Santer, a climate scientist at Lawrence Livermore National Laboratory, told the Times. "Effectively, the real world has experienced a partial cooling effect associated with this uptick in volcanic activity."

The international team observed satellite readings of temperature in the lower troposphere (the 11-mile-thick mass of air closest to Earth's surface) and compared them with 28 climate models.

Contrary to a study from last year published in the journal Nature, which attributed the lull in global warming to changes in the Pacific Ocean oscillation cycling the heat from the troposphere to the ocean's water, Santer and colleagues discovered volcanoes' secret benefits.

"When you get a big volcano that injects sulfur dioxide into the stratosphere, into the upper atmosphere, that sulfur dioxide forms these liquid phase sulfuric acid droplets, those reflect incoming sunlight back to space, they cool the lower atmosphere and surface, and when they cool the ocean surface, the recovery takes years," Santer explained.

But these periods of slow warming while the ocean "rebounds" from the cooling only last for so long before the "slow, inexorable warming" resumes, he adds.

"Volcanoes give us only a temporary respite from the relentless warming pressure of continued increases in CO2," said Piers Foster, a climate scientist at the University of Leeds, who was not involved in the study.