In a new study, NASA climate simulation suggests that extremely large volcanic eruptions called “flood basalt eruptions” could devastate the ozone layer that shields life from the Sun’s ultraviolet radiation and significantly warm Earth’s climate.
The research was published in Geophysical Research Letters and contradicts previous studies indicating these volcanoes cool the climate.
"We expected intense cooling in our simulations," said Scott Guzewich of NASA's Goddard Space Flight Center in Greenbelt, Maryland, in a NASA media release. "However, we found that a brief cooling period was overwhelmed by a warming effect," he added.
The researchers used the Goddard Earth Observing System Chemistry-Climate Model to simulate a four-year-long phase of the Columbia River Basalt (CRB) eruption that occurred between 15 million and 17 million years ago in the Pacific Northwest of the United States.
Flood basalts are regions with a series of century-long eruptive episodes and occur over periods of hundreds of thousands of years, sometimes even longer.
Some of these eruption events have happened at about the same time as mass-extinction events, and many are associated with extremely warm periods in Earth's history. They also appear to have been common on other terrestrial worlds in our solar system, such as Mars and Venus. Although Mars and Venus may have had oceans of water in the distant past, both are currently very dry. Scientists are investigating how these worlds lost most of their water to become inhospitable for life.
“Eruptions like the one we simulated would emit massive amounts of sulfur dioxide gas. Chemistry in the atmosphere quickly converts these gas molecules to solid sulfate aerosols. These aerosols reflect visible sunlight, which causes the initial cooling effect, but also absorb infrared radiation, which warms the atmosphere aloft in the upper troposphere and lower stratosphere. Warming this region of the atmosphere allows water vapor to get mixed into the stratosphere. We see a 10,000% increase in stratospheric water vapor. Water vapor is a very effective greenhouse gas, and it emits infrared radiation that warms the planet’s surface,” said Guzewich.
It should also be noted that flood basalts also release carbon dioxide, a greenhouse gas as well, but they don’t appear to emit enough to cause the extreme warming associated with some eruptions.
The excess heating from stratospheric water vapour could provide an explanation for this as well.