Thursday, August 15, 2013

New paper projects a decrease of tropical cyclones over the 21st century

A paper published today in the Journal of Climate projects a 3-15% decrease of tropical cyclones over the 21st century. Contrary to the claims of climate alarmists, many peer-reviewed papers have documented a decrease in the frequency of cyclones or hurricanes, with little to no change of intensity, and project fewer hurricanes/cyclones in the future.

Projected changes in late 21st century tropical cyclone frequency in thirteen coupled climate models from the Coupled Model Intercomparison Project Phase 5

K. J. Tory,1 S. S. Chand,2 J. L. McBride,1,3 H. Ye,1 and R. A. Dare1
1 Centre for Australian Weather and Climate Research, Bureau of Meteorology, Melbourne, Victoria, Australia
2 School of Science, Information Technology & Engineering, University of Ballarat, Ballarat, Victoria, Australia.
3 Department of Earth Sciences, University of Melbourne, Parkville, Victoria, Australia

Changes in tropical cyclone (TC) frequency under anthropogenic climate change are examined for thirteen global models from the Coupled Model Intercomparison Project Phase 5 (CMIP5), using the OWZP TC detection method developed by the authors in earlier papers. The method detects large-scale conditions within which TCs form. It was developed and tuned in atmospheric reanalysis data, and then applied without change to the climate models to ensure model and detector independence. Changes in TC frequency are determined by comparing TC detections in the CMIP5 historical runs (1970—2000) with high emission scenario (representative concentration pathway 8.5) future runs (2070—2100). A number of the models project increases in frequency of higher latitude tropical cyclones in the late 21st century. Inspection reveals these high latitude systems were subtropical in origin and are thus eliminated from the analysis using an objective classification technique. 
TC detections in eight of the thirteen models reproduce observed TC formation numbers and geographic distributions reasonably well, with annual numbers within ±50% of observed. TC detections in the remaining five models are particularly low in number (9—27% of observed). The eight models with a reasonable TC climatology all project decreases in global TC [tropical cyclone] frequency varying between 3 and 15 %. Large inter-model and inter-basin variations in magnitude and sign are present, with the greatest variations in the Northern Hemisphere basins. These results are consistent with results from earlier generation climate models, and thus confirm the robustness of coupled model projections of globally-reduced TC [tropical cyclone] frequency.