A recent NASA-funded study has linked the 1991 eruption of the Mount Pinatubo to a strengthening of a climate pattern called the Arctic Oscillation. For two years following the volcanic eruption, the Arctic Oscillation caused winter warming over land areas in the high and middle latitudes of the Northern Hemisphere, despite a cooling effect from volcanic particles that blocked sunlight.
The Arctic Oscillation (AO)
A positive phase of the Arctic Oscillation (top) is associated with strengthening of winds circulating counterclockwise around the North Pole north of 55°N, that is, roughly in line with Moscow, Belfast, and Ketchikan, Alaska. In winter these winds pull more warm air from oceans to continents causing winter warming, and like a top spinning very fast, they hold a tight pattern over the North Pole and keep frigid air from moving south. Cool winds sweep across eastern Canada while North Atlantic storms bring rain and mild temperatures to Northern Europe. Drought conditions prevail over the Mediterranean region.
During the negative phase of the Arctic Oscillation (bottom), cool continental air plunges into the Midwestern United States and Western Europe while storms bring rainfall to the Mediterranean region. Credit: David W. J. Thompson, J. M. Wallace
Eruption of Mount Pinatubo, Philippines, July 1991
Strong explosive volcanic eruptions, like ones of the Mt. Pinatubo in Philippines in June 1991, inject millions of ton of sulfur dioxide gas at the altitudes of about 15 miles where it interacts with water vapor producing a volcanic aerosol layer that consists of tiny droplets of highly concentrated sulfuric acid.
As a result of the Pinatubo eruption, globally averaged surface temperature decreased by about 0.3 Kelvin (0.3 Celsius) for two years after the eruption and the temperature in the tropical lower stratosphere increased by about 2-3 Kelvin (2-3 Celsius). The tropospheric response over most land areas in the Northern Hemisphere is characterized by summer cooling and winter warming. Credit: U.S. Geological Survey, J.N. Marso, July 1991
One mission of NASA’s Earth Science Enterprise, which funded this research, is to better understand how the Earth system responds to human and naturally-induced changes, such as large volcanic eruptions.
“This study clarifies the effect of strong volcanic eruptions on climate, important by itself, and helps to better predict possible weather and short-term climate variations after strong volcanic eruptions,” said Georgiy Stenchikov, a researcher at Rutgers University’s Department of Environmental Sciences, New Brunswick, N.J., and lead author on a paper that appeared in a recent issue of the Journal of Geophysical Research.
Krishna Ramanujan | NASA/Goddard Space Flight Center
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