Global Wanning, Climate Change and Cyclone Related Destructive Winds - Discussion of Results from Some Selected Studies with Emphasis on the North Indian Ocean

摘要

Global warming due to concentration of greenhouse gases is a reality. Consequent changes are likely in the ocean and earth-atmosphere systems. This raises the apprehension of future increases in the frequency of high-velocity winds generated by weather systems, like tropical cyclones, and their destructive potentials.rnOur present knowledge on the subject is inadequate and incomplete. The projections available through different climate models are at variance. Nevertheless, if past behaviour is an indication of the future, then it should be possible to project likely changes in high-velocity winds generated by tropical cyclones through the analysis of past data.rnWith this in view, we analyzed historical data on tropical cyclones, which are one of the sources of high velocity winds in the tropics, for the period of 1891 to 2008 along with recent sea-surface temperature data of the North Indian Ocean region (the Bay of Bengal and Arabian Sea). It has been observed that though the sea-surface temperature in the North Indian Ocean region (NIO) is increasing (as projected by global circulation models), the frequency of tropical cyclones, including intense ones, is decreasing. Analysis of estimated/observed highest maximum winds associated with TCs of very severe intensity (winds with 64 knots or more) observed every year during 1965 to 2008 in the NIO region also do not show any increasing trend. This result, though tentative (short data series), led us to conclude that there may not be any significant increase in high velocity winds and consequent coastal impact due to global warming in the NIO region. However, this does not exclude the occurrence of some individual cyclones of catastrophic nature that has been observed also in the past.