New research shows that the cooling effect that volcanic eruptions have on Earth’s surface temperature is likely underestimated by a factor of two, and potentially as much as a factor of four, in standard climate projections.
While this effect is far from enough to offset the effects of global temperature rise caused by human activity, the researchers from the University of Cambridge, say that small-magnitude eruptions are responsible for as much as half of all the sulfur gases emitted into the upper atmosphere by volcanoes.
The results suggest that improving the representation of volcanic erjuptions of all magnitudes will in turn make climate projections better.
Volcanoes play an important role in the global climate system. When volcanoes erupt, they emmit sulfur gases into the upper atmosphere, which forms tiny particles called aerosols that reflect sunlight back into space. For very large eruptions, such as Mount Pinatubo in 1991, the amount of volcanic aerosols is so large that it single-handedly causes global temperatures to drop.
However, these large eruptions only occur a handful of times per century-most small magnitude eruptions happen every year or two.
“Compared with the greenhouse gases emitted by human activity, the effect that volcanoes have on the global climate is relatively minor, but it’s important that we include them in climate models, in order to accurately assess temperature changes in future,” said lead author May Chim.
“Volcanic aerosols in the upper atmosphere typically stay in the atmosphere for a year or two, whereas carbon dioxide stays in the atmosphere for much, much longer,” said Chim. “Even if we had a period of extraordinarily high volcanic activity, our simulations show that it wouldn’t be enough to stop global warming. It’s like a passing cloud on a hot, sunny day: the cooling effect is only temporary.”
https://phys.org/news/2023-06-effect-volcanic-eruptions-significantly-underestimated.html