Climate change could cause heavier rainfall on volcanoes

The majority of Earth’s volcanoes could see heavier rainfall due to climate change which could increase eruptions and mud slides

By James Dinneen

Climate change could cause more extreme rainfall at the majority of Earth’s active land volcanoes. Rainfall has previously been implicated as a risk factor for eruptions and mudslides.

The geological record is full of volcanoes changing Earth’s climate by belching forth gasses and soot that reflect or trap radiation from the sun, such as the 1815 eruption of Mount Tambora which made 1816 the “year without a summer.” The relationship appears to go both ways: melting glaciers, sea level rise and rainfall can all affect volcanic activity.

Jamie Farquharson at the University of Strasbourg in France and Falk Amelung at the University of Miami in Florida wondered how many of the roughly 1200 active land volcanoes might get an increased amount of rainfall due to climate change.

The pair ran nine different climate models under medium and high greenhouse gas emissions scenarios, corresponding to 2-3ºC and 5ºC of warming by 2100. They then looked at where at least seven out of the nine models agreed.

Under the high emissions scenario, they found that 716 volcanoes would see an increase in heavy rainfall, including most of the Pacific “Ring of Fire”, the African Rift system and some Antarctic and Pacific volcanic island chains, and 506 in the medium emissions scenario.

In both scenarios, around a hundred volcanoes would actually see a decrease in heavy rainfall by 2100. There were also several hundred in each scenario where the models didn’t agree enough to make a determination.

The researchers also analysed decades of reports from the Smithsonian Global Volcanism Program, which catalogues volcanic activity. They found heavy rainfall had been implicated in eruptions or other hazards like mudslides for at least 174 volcanoes, including Mount Vesuvius in Italy, St. Helens in Washington and Reventador in Ecuador, all of which would get more heavy rain with warming.

Thomas Aubry at the University of Cambridge, UK says this “puts the nail in the coffin for how important rainfall is going to be for volcanic hazards.”

Heavy rainfall can induce eruptions when cold water seeps into lava domes and vaporises or by “rotting” a volcano’s internal structure over time, says Bill McGuire at University College London. Heavy rains can also cause mudslides of volcanic ash called lahars which are the most deadly volcanic hazard. “Volcanoes tend to be pretty fragile environments,” says Farquharson.

Aubry says the conditions under which increased rainfall would cause an eruption or a lahar are complex and “might change a lot from one volcano to another.” But the study demonstrates rainfall should be considered as part of volcanic hazard monitoring, he says. Meteorological data is not usually taken into account by monitors at many volcanoes.

Journal reference: Royal Society Open Science, DOI: doi/10.1098/rsos.220275