Climate change will transform cooling effects of volcanic eruptions, study suggests

Simulation of global sulfur gas concentrations in current-day and high end warming scenarios. Credit: Thomas Aubry University of CambridgeScientists have demonstrated that humans-caused climate changes will have significant consequences on how volcanic gases interact in the atmosphere.Researchers from the University of Cambridge, UK Met Office and University of Cambridge claim that large-magnitude eruptions are likely to have more powerful effects as the climate warms. The cooling effects of smaller- and medium-sized eruptions may shrink by up to 75%. These smaller eruptions are more common, so further research is required to determine if the net effect will cause additional warming or cooling.Although we cannot control the location and timing of volcanic eruptions, it is possible to increase the amount of plumes of ash, gas, and other pollutants emitted from large but rare volcanic eruptions. Climate change will also increase the transport of volcanic material in the form of tiny, shiny droplets known as volcanic sulfate aerosols from the tropics up to higher latitudes.Large eruptions will result in the haze caused by volcanic aerosols blocking more sunlight from reaching Earth's surface. This can amplify the temporary cooling effect of volcanic eruptions. These results were published in Nature Communications.The effects of Mount Pinatubo's eruption in 1991 in the Philippines were felt all over the world. The plume, the second-largest of the 20th century, reached more than 30 km into the sky and formed a layer called global haze. Global temperatures dropped as much as 0.5 degrees Celsius in 1992 due to this haze. Compared to this, global temperatures have risen by more than 1 degree Celsius in the past 1850 thanks to human activities. The volcanic aerosols' effect lasts for a few years while the effects of anthropogenic greenhouse gasses will have a lasting impact on the climate for many centuries."We can see the cooling effect of volcanic eruptions going back two thousand year from the information contained within tree rings, in addition to the data we have about recent eruptions such as Pinatubo," Dr. Thomas Aubry, a Cambridge geographer and the paper's first author, said. "How could a warming climate impact the cooling caused by volcanic eruptions?"Like hot air balloons, volcanic plumes rise to the point where they are naturally buoyant. The Cambridge study examined how high these plumes could rise in the atmosphere and how they would be transported around the world under different warming conditions.To simulate the effects of climate change on aerosols from volcanic eruptions, researchers combined global climate models with volcanic plume modeling.The researchers found that climate change can cause plumes to rise higher, aerosols to spread more quickly around the globe and large eruptions such as Mount Pinatubo (which occur only once or twice per year), resulting in a cooling effect amplified to 15%. Climate change is expected to amplify the cooling. The melting of ice sheet is projected to increase the frequency and size of volcanic eruptions in Iceland.The effect of moderate-sized eruptions, such as the 2011 Nabro in Eritrea's eruption, will decrease by approximately 75% under high-end warming scenarios. The reason is that the tropopause, the boundary between the troposphere below it and the stratosphere below it, will rise. This will make it more difficult for volcanic plumes reach the stratosphere. The climatic effects of volcanic plumes trapped in the troposphere's aerosols are minimal and localized. They can be washed away by precipitation within a few weeks."Climate Change is not something that's comingit’s already here, as clearly shown by this week’s IPCC Report," stated Dr. Anja Schmidt, also from Department of Geography. The effects of climate change, and some of its feedback loops, are becoming more apparent. However, the climate system is complicated. Understanding all of these feedback loops is crucial for understanding the planet and making accurate climate projections.Aubry stated that the IPCC has not yet accounted for "the new feedback loops between climate change and volcanic eruptions we have highlighted in this work." It could shed light on future volcanic influences on climate. Even though volcanoes may have a small impact on climate relative to human greenhouse gas emissions they still play an important role in the system.Schmidt is also affiliated to the Yusuf Hamied Department of Chemistry. Schmidt said, "Dues to more frequent, more intense wildfires as well as other extreme situations, the composition of upper atmosphere is changing before our eyes." "As we continue releasing greenhouse gases, the interaction of volcanic emissions with the atmosphere will continue changing. It is crucial to quantify these interactions to understand climate variability.They hope to gather more scientists and volcanologists to better understand the mechanisms behind volcanic plume rise, aerosol lifecycle and how changes in eruption frequency, magnitude and precipitation will affect the future climate effects of volcanic eruptions.Continue reading Sea levels can influence volcanic island eruptionsAdditional information: Climate change modulates stratospheric volcano sulfate aerosol lives and radiative forcing of tropical eruptions, Nature Communications (2021). Information from Nature Communications: Climate change modulates stratospheric volcano sulfate aerosol lives and radiative forcing of tropical eruptions. DOI: 10.1038/s41467-021-24943-7