Volcanoes, weather can affect global temps

SASKATOON, Saskatchewan, July 6 (UPI) -- Relatively small volcanic eruptions can affect global temperatures when material is carried into the atmosphere by weather systems, Canadian researchers said.

Until now it was thought that only a massively energetic volcanic eruption could inject aerosols past the troposphere, the turbulent atmospheric layer closest to the Earth, into the stable layers of the stratosphere higher up, researchers at the University of Saskatchewan said.

"If an aerosol is in the lower atmosphere, it's affected by the weather and it precipitates back down right away," atmospheric scientist Adam Bourassa said.

But strong weather systems such as monsoon can boost aerosols from even small eruptions to great heights, researchers said.

Scientists examined the June 2011 eruption of the Nabro volcano in Eritrea in northeast Africa, and found wind carried the volcanic gas and aerosol -- minute droplets of sulfuric acid -- into the path of the annual Asian summer monsoon that lifted it high into the stratosphere.

"Once it reaches the stratosphere, it can persist for years, and with that kind of a sustained lifetime, it can really have a lasting effect," Bourassa said.

That effect is the scattering of incoming sunlight and the potential to cool the Earth's surface, such as was seen in the 1991 eruption of Mount Pinatubo in the Philippines that temporarily dropped temperatures worldwide, researchers said.