Reference
Englehart, P.J., Lewis, M.D. and Douglas, A.V. 2008. Defining the frequency of near-shore tropical cyclone activity in the eastern North Pacific from historical surface observations (1921-2005). Geophysical Research Letters 35: 10.1029/2007GL032546.
Background
The authors note that much attention has been paid "to the possibility that warming in sea surface temperatures globally is associated with positive trends in tropical cyclone [TC] intensity and the number of extreme TCs," in spite of the fact that "trends in TC activity are not consistent from basin to basin despite the evidence for broad warming," and that "substantive concerns exist regarding the consistency and reliability of measurements used to infer TC intensity."
What was done
In an effort to cast further light on the subject, Englehart et al. developed what they call a "first cut" data set pertaining to the area immediately adjacent to Mexico's Pacific coast. Although noting that only 54% of the total number of Eastern Pacific storms reached TC status within this near-shore area over the period 1967-2005, they indicate that "near-shore storm activity is fairly well correlated with total basin TC activity, a result which suggests that over the longer period (i.e., 1921-onward), changes in near-shore activity can provide some sense of the broader basin activity."
What was learned
The three researchers' analyses revealed the existence of significant decadal variability in annual eastern Pacific near-shore TC frequency of occurrence. In addition, they found that "long-term TC frequency exhibits a significant (p = 0.05) negative trend," which -- as best we can determine from their graph of the data -- declines by approximately 23% over the 85-year period 1921-2005. This result was driven solely by an approximate 30% drop in TC frequency during the late (August-November) TC season, with essentially no long-term trend in the early (May-July) TC season. They also present a graph of the maximum wind speed associated with each TC, from which we calculate an approximate 20% decline in this intensity-related parameter over the period of their study.
What it means
Although Englehart et al.'s work is acknowledged by them to be but a "first cut" at trying to determine how North Pacific TCs may have varied in frequency of occurrence and intensity over the last 85 years, they provide absolutely no support for climate-alarmist claims that global warming increases both the frequency and intensity of TCs and/or hurricanes. In fact, the data from this part of the world seem to suggest just the opposite.