Volcanic eruptions will not affect future climate in the same way

Volcanoes have a definite influence on the climate, but can the same be said of the reverse relationship? In particular, will the ongoing warming change the way the climate system responds to volcanic eruptions? Researchers have recently taken an interest in the question. Their results are published in the journal Nature communications this August 12.

Explosive volcanic eruptions can have a profound impact on the climate by injecting large amounts of sulfur dioxide (SO2) in the stratosphere. Indeed, by reacting with water vapor, the SO2 will form aerosols sulphates very effective in reflecting incident solar radiation back to space.

As the stratosphere is very stable and devoid of precipitation, these aerosols can stay there from a few months to several years and cover almost the entire globe if they are injected into a tropical region. The associated increase in the reflective power of the planet leads to a drop in temperature and a decrease in precipitation overall average. In the case of Pinatubo (Philippines) in 1991, for example, an average temperature decrease of about 0.5 ° C was observed during the months following the eruption.

Increased sensitivity to strong volcanic eruptions

However, a group of researchers fromCambridge University (England) has shown that with global warming, the climatic influence of large-scale eruptions will be amplified. In question ? The elevation of the tropopause combined with an acceleration of winds in the stratosphere. As a result, volcanic plumes rise higher and sulphate aerosols are dispersed more rapidly around the globe. Using a climate-chemistry model, the authors suggest that surface cooling would be amplified by about 15%.

“The new feedback loops between climate and volcanic eruptions that we highlight in this work are currently not taken into account byr le IPCC » says Thomas J. Aubry, main author of the paper. “This could shed new light on the evolution of volcanic influences on the climate. Even though volcanoes have a limited influence on the climate in relation to human greenhouse gas emissions, they are an important part of the system ”.

An asymmetry of size

However, it is different when you consider explosive eruptions that are smaller in magnitude, but also occur more frequently. In this case, the plumes, which are less energetic, have a much harder time reaching the stratosphere as the tropopause rises. However, by remaining confined to the troposphere, aerosols are quickly stirred and washed away by precipitation. The influence on the climate therefore remains very limited. If nothing is done to strongly limit global warming, the surface cooling associated with these smaller amplitude eruptions would be decreased up to 75%.

“As we continue to emit greenhouse gases, the way volcanic emissions interact with the atmosphere will continue to change and it is important to quantify these interactions in order to fully understand climate variability”, adds Anja Schmidt, co-author of the study. Future work will be needed to refine these results and attempt to determine whether the net climate effect is dominated by intense (but rare) eruptions or by weaker (but also more frequent) eruptions.

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