Hotspot volcanoes

How will climate change affect volcanoes?

British researchers have started to unravel the complex relationship between volcanic eruptions and climate change, showing that the temperature of the atmosphere affects the spread of ash and gases.

One of the most massive volcanic eruptions of the 20and century was that of Mount Pinatubo in the Philippines. When it exploded in 1991, it spewed clouds of gas and dust more than 30 kilometers into the atmosphere, putting more particles into the stratosphere than any eruption since Krakatoa in 1883.

This created a hazy layer that wrapped around the world, blocked some sunlight from reaching the Earth’s surface, and ultimately caused global temperatures to drop by 0.5 degrees Celsius between 1991 and 1993.

Now a team of researchers from the University of Cambridge and the UK Met Office have studied the current effects of climate on such eruptions.

“We wanted to approach the question from the opposite angle: how could a warming climate affect the cooling of volcanic eruptions? says Thomas Aubry of the University of Cambridge.

Volcanic eruptions like Mount Pinatubo in 1992 will now have different effects under climate change. Credit: ARLAN NAEG/Stringer/Getty Images.

Aubry is the first author of a study published in Nature Communicationwho used a combination of global climate models and volcanic plume models to answer this question.

The team found that a warmer atmosphere will cause gas and dust plumes from large eruptions to rise even higher, and that aerosols will also spread faster from the tropics to higher latitudes. The combined effect will further block sunlight and cause temporary cooling, with the effect being amplified by 15%. The study also notes that as the ocean warms, cooling may increase further.

However, the team also looked at small and medium eruptions and found that in a high-end emissions scenario, climate change could actually reduce cooling effects by up to 75%. As the atmosphere warms, the tropopause (the boundary between the troposphere and the stratosphere) is expected to increase in altitude and make it harder for plumes to reach the upper atmosphere and circulate around the globe.

Smaller eruptions are more common than larger ones, which only happen once or twice a century, but it’s unclear if we’d see a net warming or cooling effect – the team didn’t yet calculated the numbers on this.

It’s a complex area of ​​study, but one we need to address, they say.

“Climate change is not something that is coming – it is already here, as this week’s IPCC report clearly demonstrates,” said co-author Anja Schmidt, also from Cambridge.

“The effects of climate change and some of the feedback loops it can cause are becoming more evident now. But the climate system is complex: understanding all of these feedback loops is key to understanding our planet and making accurate climate projections.

Aubry adds: “The new feedback loops between climate and volcanic eruptions that we highlight in this work are not currently considered by the IPCC. It could shed new light on the evolution of future volcanic influences on the climate. Even though volcanoes have a limited influence on climate relative to human greenhouse gas emissions, they are an important part of the system.

Interestingly, as the ice caps melt in places like Iceland, the size and frequency of eruptions can increase; there is evidence that melting ice at the end of the last ice age triggered an acceleration in volcanic activity. Additionally, events like forest fires and extreme rainfall also alter the atmosphere, with unknown consequences for volcanic eruptions.

“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,” Schmidt says.

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