New research by a team of scientists at NASA and the University of Columbia, USA, suggests that volcanic super eruptions, like the one that formed the Yellowstone Crater in Wyoming about 2 million years ago, may not be the extinction level events we have been led to believe.
The findings, revealed in an article entitled “Severe Global Cooling After Volcanic Super-Eruptions? The Answer Hinges on Unknown Aerosol Size,” were published in the Journal of Climate.
Volcanic winter
Volcanic super eruptions involve the release of more than 1,000 cubic kilometres (240 cubic miles) of magma. They happen seldom, with the last one occurring over 22,000 years ago in New Zealand. And 52,000 years before that, the Toba volcano in Indonesia erupted 1,000 times more fiercely than 1980’s Mount St Helens eruption, whose lateral blast devastated areas up to 31 km away (19 miles). The Toba explosion, for comparison, would have covered most of the globe in volcanic material.
These eruptions also send huge clouds of gas and ash into the atmosphere, including plumes of sulfur dioxide, which condenses high in the atmosphere into small particles that can block sunlight, an effect which has long caused the scientific community to theorise about a further super-cooling effect on the planet, a so-called “volcanic winter” or New Ice Age that could wipe out humanity.
Size does matter
Size does matter, when it comes to these aerosol particles. Small particles block more sunlight but it has been difficult to trace the size of particles released in plumes from supervolcanoes tens of thousands of years ago, meaning that estimates of cooling rates have varied hugely.
The new simulations use advanced computer modelling over a range of particle sizes and have come up with the surprising view that “no single super-eruption has produced firm evidence of global-scale catastrophe for humans or ecosystems,” according to lead author Zachary McGraw. If another Toba occurred, the model suggests it would cause a drop in global temperature of 1.5 degrees Celsius, which McGraw described as “relatively modest”.
Implications for geoengineering advocates
The news may seem reassuring, but it could have negative implications for the nascent community who propose that injecting particles into the atmosphere could be a temporary fix to global warming. With particles capable of warming the planet by trapping the sun’s heat as well as cooling the planet by reflecting it, further research into volcanic eruptions is needed, some scientists have said, to explore the potential applications and consequences of attempting to control the climate through geoengineering.