Human contribution to more-intense precipitation extremes (Nature)

[jpak]

http://www.nature.com/nature/journal/v470/n7334/full/nature09763.html

Seung-Ki Min, Xuebin Zhang,Francis W. Zwiers Gabriele C. Hegerl (2011) Nature Volume:470,Pages:378–381

Abstract

Extremes of weather and climate can have devastating effects on human society and the environment1, 2. Understanding past changes in the characteristics of such events, including recent increases in the intensity of heavy precipitation events over a large part of the Northern Hemisphere land area3, 4, 5, is critical for reliable projections of future changes. Given that atmospheric water-holding capacity is expected to increase roughly exponentially with temperature—and that atmospheric water content is increasing in accord with this theoretical expectation6, 7, 8, 9, 10, 11—it has been suggested that human-influenced global warming may be partly responsible for increases in heavy precipitation3, 5, 7. Because of the limited availability of daily observations, however, most previous studies have examined only the potential detectability of changes in extreme precipitation through model–model comparisons12, 13, 14, 15. Here we show that human-induced increases in greenhouse gases have contributed to the observed intensification of heavy precipitation events found over approximately two-thirds of data-covered parts of Northern Hemisphere land areas. These results are based on a comparison of observed and multi-model simulated changes in extreme precipitation over the latter half of the twentieth century analysed with an optimal fingerprinting technique. Changes in extreme precipitation projected by models, and thus the impacts of future changes in extreme precipitation, may be underestimated because models seem to underestimate the observed increase in heavy precipitation with warming

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deniers suck

yup

[OKIsItJustMe]

1. NY Times

http://www.nytimes.com/2011/02/17/science/earth/17extreme.html?_r=1

Heavy Rains Linked to Humans

By JUSTIN GILLIS
Published: February 16, 2011

An increase in heavy precipitation that has afflicted many countries is at least partly a consequence of human influence on the atmosphere, climate scientists reported in a new study.

In the first http://www.nature.com/news/2011/110216/full/470316a.html">major paper of its kind, the researchers used elaborate computer programs that simulate the climate to analyze whether the rise in severe rainstorms, heavy snowfalls and similar events could be explained by natural variability in the atmosphere. They found that it could not, and that the increase made sense only when the computers factored in the effects of greenhouse gases released by human activities like the burning of fossil fuels.

As reflected in previous studies, the likelihood of extreme precipitation on any given day rose by about 7 percent over the last half of the 20th century, at least for the land areas of the Northern Hemisphere for which sufficient figures are available to do an analysis.

The principal finding of the new study is “that this 7 percent is well outside the bounds of natural variability,” said Francis W. Zwiers, a Canadian climate scientist who took part in the research. The paper is being published in Thursday’s edition of the journal Nature.

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