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Natural climate swings contribute more to increased monsoon rainfall than global warming
http://www.eurekalert.org/pub_releases/2013-03/uoh-ncs032013.php[font face=Serif]Public release date: 20-Mar-2013
Contact: Gisela Speidel
gspeidel@hawaii.edu
University of Hawaii ‑ SOEST
[font size=5]Natural climate swings contribute more to increased monsoon rainfall than global warming[/font]
[font size=3]Natural swings in the climate have significantly intensified Northern Hemisphere monsoon rainfall, showing that these swings must be taken into account for climate predictions in the coming decades. The findings are published in the March 18 online publication of the Proceedings of the National Academy of Sciences.
…
Wang and his colleagues, however, found that over the past 30 years, the summer monsoon circulation, as well as the Hadley and Walker circulations, have all substantially intensified. This intensification has resulted in significantly greater global summer monsoon rainfall in the Northern Hemisphere than predicted from greenhouse-gas-induced warming alone: namely a 9.5% increase, compared to the anthropogenic predicted contribution of 2.6% per degree of global warming.
Most of the recent intensification is attributable to a cooling of the eastern Pacific that began in 1998. This cooling is the result of natural long-term swings in ocean surface temperatures, particularly swings in the Interdecadal Pacific Oscillation or mega-El Niño-Southern Oscillation, which has lately been in a mega-La Niña or cool phase. Another natural climate swing, called the Atlantic Multidecadal Oscillation, also contributes to the intensification of monsoon rainfall.
"These natural swings in the climate system must be understood in order to make realistic predictions of monsoon rainfall and of other climate features in the coming decades," says Wang. "We must be able to determine the relative contributions of greenhouse-gas emissions and of long-term natural swings to future climate change."
…[/font][/font]
http://dx.doi.org/10.1073/pnas.1219405110Contact: Gisela Speidel
gspeidel@hawaii.edu
University of Hawaii ‑ SOEST
[font size=5]Natural climate swings contribute more to increased monsoon rainfall than global warming[/font]
[font size=3]Natural swings in the climate have significantly intensified Northern Hemisphere monsoon rainfall, showing that these swings must be taken into account for climate predictions in the coming decades. The findings are published in the March 18 online publication of the Proceedings of the National Academy of Sciences.
…
Wang and his colleagues, however, found that over the past 30 years, the summer monsoon circulation, as well as the Hadley and Walker circulations, have all substantially intensified. This intensification has resulted in significantly greater global summer monsoon rainfall in the Northern Hemisphere than predicted from greenhouse-gas-induced warming alone: namely a 9.5% increase, compared to the anthropogenic predicted contribution of 2.6% per degree of global warming.
Most of the recent intensification is attributable to a cooling of the eastern Pacific that began in 1998. This cooling is the result of natural long-term swings in ocean surface temperatures, particularly swings in the Interdecadal Pacific Oscillation or mega-El Niño-Southern Oscillation, which has lately been in a mega-La Niña or cool phase. Another natural climate swing, called the Atlantic Multidecadal Oscillation, also contributes to the intensification of monsoon rainfall.
"These natural swings in the climate system must be understood in order to make realistic predictions of monsoon rainfall and of other climate features in the coming decades," says Wang. "We must be able to determine the relative contributions of greenhouse-gas emissions and of long-term natural swings to future climate change."
…[/font][/font]