Warming could slow volcanic cooling: Study

Atmospheric expansion negating gases from eruptions that reflect light and heat into space

As the Earth’s atmosphere warms, the cooling effects of volcanic eruptions may be thwarted, according to a new study from the University of British Columbia.

Large volcanic eruptions are able to spew sulphurous gases into the high reaches of the atmosphere where they reflect light and heat from the sun back into space for several years.

The problem is that the lower layers of the atmosphere are warming and expanding, so much so that 12- to 25-per-cent less volcanic gas will be able to reach the stratosphere to do this vital job, PhD student Thomas Aubry said.

By the end of this century, some volcanic plumes from large eruptions in tropical regions will not push high enough to spark the cooling effect, according to computer models based on climate scenarios created by the Intergovernmental Panel on Climate Change.

“Volcanic eruptions also release carbon dioxide into the atmosphere and that can have a warming effect, but on a 100-million-year time scale,” Aubry said.

“That effect is negligible compared with the cooling effect of sulphur gases.” That is, if the gases can get there at all. Aubry’s modelling projects that a CO2 concentration above 600 parts per million in our air will trigger changes in the way volcanic plumes rise through the layers of the atmosphere.

North Pole staying warm, Page 30

The average CO2 concentration in the pre-industrial period was around 280 ppm. Earlier this year, the average hit 400 ppm and continues to rise.

“I hope that the Paris Agreement (to reduce greenhouse gas emissions) will change things and that the United States won’t exit,” Aubry said.

“Even then, it’s very uncertain what will happen with CO2 emissions.”

The effect of large volcanic eruptions is believed to have contributed to a period of global glaciation about 700 million years ago, so an uptick in large volcanic eruptions could head off a global warming feedback loop.

Several recent eruptions may have already slowed the rate of global warming in the past 10 to 15 years, but the intensity and frequency of future eruptions is murky at best, he said.