Climate Science

Backdrop for the Future

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Science  20 Apr 2007:
Vol. 316, Issue 5823, pp. 343
DOI: 10.1126/science.316.5823.343a

One of the most frequently invoked potential effects of global warming is an abrupt change in precipitation patterns. In order to assess the onset of such a change, it is necessary to have baseline knowledge of the variability of precipitation in the past. Narisma et al. have analyzed the record of global rainfall for the 20th century in order to establish the spatial and temporal distributions of abrupt decreases in rainfall over that period. They find that about 30 regional instances of large, sudden decreases in precipitation have occurred over the past 100 years, all of which deviated from the climatological norm by at least 10% and lasted for 10 years or more. The authors also observe that these sudden decreases in rainfall occurred mostly in arid and semi-arid regions, which is consistent with the results of climate modeling studies, and they suggest that this finding could be a consequence of a strong positive feedback between vegetation and climate. — HJS

Geophys. Res. Lett. 34, L06710 (2007).

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