The IPCC report was issued in 1998. There have been other reports since then. Below are some excerpts from the the 2001 IPCC Workshop on Changes in Extreme Weather and Climate Events ( http://www.ipcc.ch/pub/extremes.pdf)
The IPCC working group goes to a great deal of effort to explain why we simply do not have enough information to make pronouncements one way or the other. So, saying that global warming is causing an increase in tropical cyclone strength or frequency is unsupportable; but so is saying the opposite (like the CNN story tried to claim, in essence).
Frequency of tropical cyclones (TC) has been used as an indicator of climate change in general circulation models. The group identified a number of key gaps in our existing knowledge.
• Method of counting TCs in global models
• Unrealistic present-day climatology
• Inconsistent sign of change in enhanced CO2 environment
• Mechanisms of TC genesis in large-scale modelsThere is a lack of consistency in the techniques used for counting TCs in climate models and results may be sensitive to the method used.Clearly, the IPCC recognizes that we simply don't know enough about the very basics of cyclones to make pronouncements are how global warming affects them, for one side or the other. The whole report is an interesting read. It , at least, attempts to identify the questions which need to be asked before we can ever begin to start finding answers.Observed records of tropical cyclone activity are short and there are many problems with homogeneity. Consistent satellite data are only available since the 1960s and regions where longer-term statistics are available show large interdecadal variability in cyclone activity. Palaeoreconstruction of tropical cyclone activity has a number of problems but has potential relevance to the climate change issue. Inhomogeneities in the historical records of environmental variables, such as atmospheric temperature, limit the extent to which we can assess historical activity via maximum potential intensity (MPI) analyses.![]()
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