Wednesday, December 19, 2012

New paper finds IPCC climate models substantially exaggerate wind speeds

A paper published today in the Journal of Geophysical Research compares observations of wind speeds over China from 1971-2005 to the results from 9 IPCC AR5 climate models for the same period and finds that all 9 models show a "substantial positive bias," i.e. a substantial exaggeration, of wind speeds. The paper adds to many other peer-reviewed papers demonstrating that IPCC climate models greatly exaggerate extreme weather, cyclone activity, wind storms, droughts, and floods.

Key Points
  • Nine CMIP-5 AOGCMs display positive bias in near-surface wind speeds over China
  • The AOGCMs do not indicate any long-term tendency over the historical period
  • Projected wind climates over China are insensitive to the RCP scenario applied
Lian Chen
Sara C. Pryor
Dongliang Li
The ability of nine current generation (CMIP-5) coupled Atmosphere-Ocean General Circulation Models (AOGCMs) to accurately simulate the near-surface wind climate over China is evaluated by comparing output from the historical period (1971−2005) with an observational data set and reanalysis output. Results suggest the AOGCMs show substantial positive bias in the mean 10-m wind speed relative to observations and the ERA-40, NCEP/DOE and NCEP/NCAR reanalysis. Given the models generally produce the upper-level geopotential height gradients comparative well, it is postulated that one major reason for the discrepancy between observed and modeled wind fields is the surface characterization used in the AOGCMs. All models exhibit lower inter-annual variability than reanalysis data and observations, and none of the models reproduce the recent decline in wind speed manifest in the near-surface observations. The wind speed of individual model runs during the historical period do not exhibit much influence from the initial atmospheric conditions. Output for the current century from seven of the AOGCMs is examined relative to the contemporary wind climate. The results indicate that spatial fields of wind speed at end of the 21st century are very similar to those of the last 35 years with comparatively little response to the precise Representative Concentration Pathway scenario applied.

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