Scientific Nature: Researchers Use Volcanic Eruption as Climate Lab

When Mount Pinatubo erupted in 1991 it left a trail of evidence in the skies that is helping scientists decipher the workings of the global climate

Earth's climate cannot be replicated in a lab. So to understand how this critical component of the planet's heat regulation works, scientists must rely on "natural experiments." Such natural experiments take apocalyptic form, such as the eruption of Mount Pinatubo in the Philippines in June 1991 that sent 10 cubic kilometers of ash, gas and other materials sky high. By tracking how this eruption affected the global climate--and determining how to trace its footprint in other records--scientists have turned the catastrophe into a tool for comprehension. "The big problem with climate--and trying to study it--is you can't play with it in the lab," says atmospheric scientist Joanna Futyan of Columbia University. "We were trying to use this abrupt event as a natural experiment: something dramatic happened and you can look at how the atmosphere responds to it."

Futyan and physicist John Harries of Imperial College London analyzed how the atmosphere's humidity and temperature responded to the eruption as well as the overall radiative balance of the planet--in other words, the difference between the energy in sunlight absorbed by Earth versus the amount radiated back to space. The spectrum of this energy sent back into space from the surface (measured via satellite) has changed in the past 30 years as part of global warming, but the rate and magnitude of this change remain difficult to measure and rely on a variety of atmospheric processes, such as the amount of water vapor.