A new study has found that the cooling effect of volcanic eruptions on the Earth’s surface temperature is being underestimated by climate projections. Researchers from the University of Cambridge have found that this effect is likely underestimated by a factor of two and potentially as much as a factor of four in standard climate projections. Although this effect is not enough to offset the human-generated carbon emissions, the researchers suggest that improving the representation of volcanic eruptions of all magnitudes will make climate projections more robust.
The Role of Volcanoes in the Global Climate System
Volcanoes play an important role in the global climate system. When volcanoes erupt, they release sulfur gases into the upper atmosphere, which forms tiny particles called aerosols that reflect sunlight back into space. Large eruptions, such as Mount Pinatubo in 1991, cause global temperatures to drop. However, such eruptions happen only a few times per century, and most small-magnitude eruptions occur every year or two. Small-magnitude eruptions are responsible for as much as half of all the sulfur gases emitted into the upper atmosphere by volcanoes.
Impact on Climate and Climate Projections
The researchers used the latest ice-core and satellite records to generate 1,000 different scenarios of future volcanic activity, representing lower, median, and high levels of volcanic activity. They then performed climate simulations using the UK Earth System Model. The simulations show that the impacts of volcanic eruptions on climate, including global surface temperature, sea level, and sea ice extent, are underestimated because current climate projections largely overlook the effects of small-magnitude eruptions. For the median future scenario, the effect of volcanoes on the atmosphere, known as volcanic forcing, is being underestimated in climate projections by as much as 50%, due in large part to the effect of small-magnitude eruptions. The researchers stress that even if there were a period of extraordinarily high volcanic activity, it would not be enough to stop global warming.
Importance of Fully Accounting for the Effect of Volcanoes
The researchers say that fully accounting for the effect of volcanoes can help make climate projections more robust. They are now using their simulations to investigate whether future volcanic activity could threaten the recovery of the Antarctic ozone hole, and in turn, maintain relatively high levels of harmful ultraviolet radiation at the Earth’s surface.
While volcanic eruptions have a cooling effect on the Earth’s surface temperature, it is not enough to offset the human-generated carbon emissions. However, small-magnitude eruptions are responsible for as much as half of all the sulfur gases emitted into the upper atmosphere by volcanoes. The researchers stress that fully accounting for the effect of volcanoes can help make climate projections more robust.
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