Thursday, January 24, 2013

New paper finds IPCC climate models have 'wide disagreement about the sign of change' for precipitation

A paper published today in the Journal of Geophysical Research finds that the IPCC climate models do not agree on whether precipitation will increase or decrease in some regions. According to the authors, "Particularly for the precipitation-based indices, there can be a wide disagreement about the sign of change between the models in some regions. "

Climate extreme indices in the CMIP5 multi-model ensemble. Part 2: Future climate projections

J. Sillmann1,*,
V. V. Kharin1,
F. W. Zwiers2,
X. Zhang3,
D. Bronaugh4

Abstract
This study provides an overview of projected changes in climate extreme indices defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). The temperature- and precipitation-based indices are computed with a consistent methodology for climate change simulations using different emission scenarios in the Coupled Model Intercomparison Project Phase 3 (CMIP3) and Phase 5 (CMIP5) multi-model ensembles. We analyze changes in the indices on global and regional scales over the twenty-first century relative to the reference period 1981–2000. In general, changes in indices based on daily minimum temperatures are found to be more pronounced than in indices based on daily maximum temperatures. Extreme precipitation generally increases faster than total wet-day precipitation. In regions, such as Australia, Central America, South Africa and the Mediterranean region, increases in consecutive dry days coincide with decreases in heavy precipitation days and maximum consecutive 5-day precipitation, which indicates future intensification of dry conditions in these regions. Particularly for the precipitation-based indices, there can be a wide disagreement about the sign of change between the models in some regions. Changes in temperature and precipitation indices are most pronounced under RCP8.5, with projected changes exceeding those discussed in previous studies based on SRES scenarios. The complete set of indices is made available via the ETCCDI indices archive to encourage further studies on the various aspects of changes in extremes.

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