January 14, 2010

Listening to Johnny Chan

Filed under: Climate Extremes, Hurricanes

OK – who is Johnny Chan? Thanks to ESPN stations, many Americans have come to know Johnny Chan as one of the world’s best and most entertaining poker players. He is on television as much as Tiger Woods, still going strong since winning the championship event of the World Series of Poker in 1987 and 1988. Chan has won 10 overall World Series of Poker bracelets thereby tying him for second with the great Doyle Brunson in that category. Chan was inducted into the Poker Hall of Fame in 2002, and he appeared as himself in the movie Rounders. You might be wondering what Johnny Chan has to do with the climate change debate … well, it depends on which Johnny Chan we are talking about!

One of these men is Johnny Chan the poker expert and the other is Johnny Chan the hurricane expert – can you decide?

Enter the Johnny C.L. Chan who is equally famous in the world of global warming and tropical cyclones (a.k.a., hurricanes, typhoons). Dr. Chan is now Chair Professor of Applied Physics (Atmospheric Science) and Dean of the School of Energy and Environment, as well as the Director of the Guy Carpenter Asia-Pacific Climate Impact Centre all at the City University of Hong Kong. He has published over 130 international journal articles and given more than 200 invited talks and conference papers and he is also an editor of the International Journal of Climatology and Atmospheric and Oceanic Science Letters. We certainly believe he can be considered a global expert in the world of tropical cyclones.

Dr. Chan has been busy recently publishing three articles of great interest to us at World Climate Report. In his first article on tropical cyclones (TCs) we will cover, Chan and Xu begin by noting “While some recent studies have claimed that the number of intense TCs is on the increase as a result of global warming, others pointed that such a claim is not valid as the trend was calculated based on data with large uncertainties in the pre-satellite era”. Many of the studies are based on hurricanes in the Atlantic, and in this article, Chan and Xu examine TCs in East Asia over the period 1945-2004.

They conducted the analyses for sub-regions in East Asia and for all of East Asia. The graph below (Figure 1) and the following sentence from their conclusions section just about sum things up for us. Chan and Xu write “An important finding in this part of the study is that none of the time series shows a significant linear temporal trend, which suggests that global warming has not led to more landfalls in any of the regions in Asia.” We just cannot say it any better!


Figure 1. Total number of tropical cyclones and total number of landfalling tropical cyclones in East Asia (from Chan and Xu, 2009)

Next up is an article by Chan and a colleague in Japan; the Kubota and Chan team were able to construct a time series of landfalling tropical cyclones in the Phillipines (referred to as TLPs) extending from 1902 to 2005 (data are missing for the 1940-1944 years). Once again, the figure below (Figure 2) and a sentence in their conclusions section sum it all up. Kubota and Chan conclude “Annual TLP from 1902 to 2005 using the two definitions shows dominant periodicity of about 32 years before 1940 and of about 10–22 years after 1945; however, no trend is found.”


Figure 2. Number of landfalling tropical cyclones in the Phillipines (from Kubota and Chan, 2009)

In our third and final article in our Johnny Chan feature, we find a move any from time series analysis of hurricane activity to an investigation of the underlying causes of potential changes in hurricane activity. Chan notes that others are using “a parameter called the maximum potential intensity (MPI) to estimate the maximum intensity that a tropical cyclone (TC) could reach based on the atmospheric and oceanic thermodynamic conditions in which the TC is embedded. The value of MPI depends upon three factors: sea-surface temperature (SST), the outflow temperature (To) and the net available convective available potential energy (CAPE) in the troposphere. Extending this concept to the entire TC season, a higher value of MPI summed over the ocean basin implies a more energetic atmosphere, at least thermodynamically, so that more TCs could reach higher intensities. In other words, a season with a higher value of MPI should have more intense TCs. If this is true, it is possible to estimate whether the frequency of occurrence of intense TCs is increasing in response to global warming”.

Chan notes that much of the research on relating MPI to actual hurricane activity has been carried out in the Atlantic; others have found a correlation between MPI and the number of intense hurricanes to range from 0.45 to 0.63 depending on the time span selected. However, he finds “In other ocean basins, there is either no correlation or the correlation is not statistically significant. In other words, only in the Atlantic are thermodynamic factors responsible, but still only to a certain extent, for the climate variations of intense TCs. In other ocean basins, it appears that the dynamic factors are much more dominant”. Finally, he clearly states “Although it has been generally accepted that the thermodynamic energy available in the atmosphere is likely to increase under global warming, the results from this study suggest that such an increase does not necessarily imply a concomitant increase in the number of intense TCs, because how the dynamic factors will vary are still not clear. Until we can demonstrate that the dynamic factors will also become more favourable for TC intensification, it remains uncertain whether the frequency of occurrence of intense TCs will increase under a global warming scenario.”

When it comes to poker or hurricanes, we listen to Johnny Chan!

References:

Chan, J.C.L. 2009. Thermodynamic control on the climate of intense tropical cyclones. Proceedings of the Royal Society A, 465, 3011-3021.

Chan, J.C.L. and M. Xu. 2009. Inter-annual and inter-decadal variations of landfalling tropical cyclones in East Asia. Part I: time series analysis. International Journal of Climatology, 29, 1285-1293.

Kubota, H., and J. C. L. Chan. 2009. Interdecadal variability of tropical cyclone landfall in the Philippines from 1902 to 2005. Geophysical Research Letters, 36, L12802, doi:10.1029/2009GL038108.




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