Lighthill, J., G. Holland, W. Gray, C. Landsea, G. Craig, J. Evans,
Y. Kurihara, and C. Guard, 1994: Meeting Review: Global climate change
and tropical cyclones. Bulletin of the American Meteorological Society,
75(11), 2147-2157.
Abstract: This paper offers an overview of the authors' studies
during a specialized international symposium (Mexico, 22 November-1 December
1993) where they aimed at making an objective assessment of whether climate
changes, consequent on an expected doubling of atmospheric CO2
in the next six or seven decades, are likely to increase significantly
the frequency or intensity of tropical cyclones (TC). Out of three methodologies
available for addressing the question they emply two, discarding the third
for reasons set out in the appendix.
In the first methodology, the authors enumerate reasons why, in tropical
oceans, the increase in sea surface temperature (SST) suggested by climate
change models might by expected to affect either (i) TC frequency, because
a well-established set of six conditions for TC formation include a condition
that SST should exceed 26°C, or (ii) TC intensity, because this
is indicated by thermodynamic analysis to depend critically on the temperature
at which energy transfer to air near the sea surface takes place.
But careful study of both suggestions indicates that the expected effects
of increased SST would be largely self-limiting (i) because the other five
conditions strictly control how far the band of latitudes for TC formation
can be further widened, and (ii) because intense winds at the sea surface
may receive their energy input at a temperature significantly depressed
by evaporation of spray, and possibly through sea surface cooling.
In the second methodology, the authors study available historical records
that have very large year-to-year variability in TC statistics. They find
practically no consistent statistical relationships with temperature anomalies;
also, a thorough analysis of how the El Niño-Southern Oscillation
cycle influences the frequency distribution of TCs shows any direct effects
of local SST changes to be negligible.
The authors conclude that, even though the possibility of some minor indirect
effects of global warming on TC frequency and intensity cannot be excluded,
they must effectively be "swamped" by large natural variability.