2023-06-25 15:13:00
Minor eruptions
25 June 2023 15:13 Robert Klatt
Current climate models have grossly underestimated the cooling effects of volcanic eruptions, mainly because smaller eruptions were hardly taken into account. Because the cooling effect is temporary, it cannot stop global warming.
Cambridge (England). Volcanoes have a major impact on the global climate system. When a volcano erupts, it emits sulfur gases that condense into tiny particles called aerosols in the upper atmosphere. These aerosols are able to reflect sunlight back into space. During particularly massive eruptions, such as the Hunga Tonga-Hunga Ha’apai (HTHH) eruption, which produced the strongest thunderstorm on record, the volume of volcanic aerosols can be so large that it leads to a global cooling of temperatures. However, such large eruptions occur only a few times in a century, while smaller eruptions occur almost annually.
Climate forecasts, such as the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) of the United Nations (UN), assume that volcanic activity in the period from 2015 to 2100 will be at the same level as in the period of 1850 until 2014. A study by researchers led by May Chim at the University of Cambridge now shows that the effects of lower-intensity eruptions are neglected.
“Compared to the greenhouse gases released by human activities, the impact that volcanoes have on global climate is relatively small. Nevertheless, it is important to include them in climate models in order to be able to accurately assess future temperature changes.”
Analyzed ice core and satellite data
According to the publication in Geophysical Research Letters, the researchers have developed different scenarios for future volcanic activity based on ice core and satellite data. They selected scenarios representing low, medium and high levels of volcanic activity and then ran climate simulations using the UK Earth System Model.
Their simulations suggest that the effects of volcanic eruptions on climate, including global surface temperature, sea level and sea ice extent, are underestimated. The reason for this lies in the fact that current climate projections largely underestimate the possible future extent of volcanic activity.
Volcanic influence greatly underestimated
According to the study’s medium-term future scenario, the influence of volcanoes on the atmosphere is underestimated in climate forecasts by up to 50 percent. This is largely due to the effects of lower intensity eruptions.
“We found that not only is volcanic influence underestimated, but lower intensity eruptions are actually responsible for up to half of the volcanic influence. Individually, these lower-intensity eruptions may not have a measurable effect, but taken together, their effect is significant. I was surprised to see how important these lower intensity eruptions are. We knew they had an effect, but we didn’t know it was that big.”
Although the cooling effect of volcanoes is underestimated in climate projections, the researchers emphasize that it is not comparable to human-caused carbon emissions.
“Volcanic aerosols in the upper atmosphere typically stay in the atmosphere for one to two years, while carbon dioxide stays much, much longer. Even if we had a period of exceptionally high volcanic activity, our simulations show that this would not be enough to halt global warming. It’s like a passing cloud on a hot, sunny day: the cooling effect is temporary.”
The scientists believe that fully accounting for the effects of volcanoes can help improve the reliability of climate forecasts. They are currently using their simulations to test whether future volcanic activity could interfere with regeneration of the Antarctic ozone hole and thus sustain comparatively high levels of harmful ultraviolet radiation at the Earth’s surface.
Geophysical Research Letters, doi: 10.1029/2023GL103743
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