Is global warming causing more volcanoes?

Is global warming causing an increase in volcanoes? We got that question several times after the eruption of the Eyjafjallajokull volcano in Iceland. EarthSky asked volcanologist Bjorn Oddsson in Iceland. He said “definitely not.” Science hasn’t revealed any direct correlation between volcanoes and global warming. But, he said, it’s possible to visualize a connection.

Bjorn Oddsson: It surely is getting warmer in the world, and glaciers are getting smaller and thinner. And we have volcanoes beneath glaciers. So the mass which is lying on top is getting less, if a volcano is ready to erupt, it’s more likely to erupt under thinner ice than thicker ice.

After the Iceland volcano in April 2010, some scientists called for more research into whether global warming could trigger an increase in geological hazards – volcanoes, earthquakes, landslides, tsunamis. This idea is extremely speculative. No evidence yet exists. But some believe the question deserves a deeper look. In Iceland, Oddsson said, volcanologists are asking another question – how volcanoes might affect climate, instead of the other way around. Volcanoes are known to cool climate with the ash they release. This ash – a mix of burned-up rock and water vapor – can become trapped in the atmosphere.

Bjorn Oddssen: It can cause cooling in the world. That’s what we’ve seen through the history and the centuries. It just blocks the sun out. It can cause a degree or two in temperature, which is lower for one or two years.

Oddsson said the degree of volcanoes’ cooling the atmosphere can vary. It depends on how big the volcanic eruption is, the size of the ash plume, and where winds carry the ash. He pointed to a volcanic eruption in Iceland in the 18th century that caused crops to fail in Europe

Bjorn Oddsson: They just didn’t have enough sunlight to grow.

He added that the volcano had also released major amounts of sulfur gas, which is harmful to crops. Oddsson said, currently, there’s no highly accurate way to model how volcanic ash is produced and dispersed – or the specific effects volcanoes have on weather patterns. But he said the Eyjafjallajokull volcano should provide a test case.

Bjorn Oddsson: Now we are gaining a lot of data from this volcano. We have to work with this data, and put them into the models to make them better. I’m not saying that the models are bad, I’m just saying that we have to make them better.

He reiterated that this is what science is all about.

Bjorn Oddson: To collect data, and evaluate the data, and you have the idea, and then you have a discussion about the idea.