Current warming and likely future impacts - Climate Change: Biological and Human Aspects - page 327

regional research. These regional scenarios will undoubtedly improve with further
research both in the field and with the development of more sophisticated models.
But what of the IPCC warning about surprises? This section looks at some key areas.
6.6.1 Extremeweatherevents
One swallow does not make a spring, and so a single extreme weather event (be it
an abnormally heavy downpour or a particularly dry month) does not necessarily
signify climate change. But how many swallows do? An increase in the frequency of
weather abnormalities will, at some point, signify that the climate has altered. Recent
years have seen an increasing frequency of strong hurricanes (it is thought that the
total number of all hurricanes has broadly remained the same) and record-breaking
global warmth. This last is only to be expected with (indeed, it is inherent in) global
warming. There have also been times of unusually intense local and regional rainfall.
Such events are surprising, especially for those who experience them. When a
'hurricane' hit southern England one night in 1987 it caught the population by
surprise and disrupted lives of virtually everyone for at least a day, with power cuts,
telephones not working and roads closed due to fallen trees. Not least surprised
was one meteorologist working for BBC Television as a weather presenter, Michael
Fish, whose evening broadcast prior to the storm was erroneously reassuring. Now,
whereas this particular single swallow cannot itself be attributable to climate change,
it was the sort of event that climatologists were contemplating. Indeed, the incident
was referred to by one UK Governmental department as climate change-related, even
though that claim could not be substantiated. Nonetheless, the Department of Energy
used the 1987 storms in an energy-conservation promotion, with the slogan 'Global
warming, we have been warned'. The department was subsequently reprimanded in
March 1992 by the Advertising Standards Authority (Cowie, 1998). Today there is
arguably less chance that such a reprimand would be issued.
Having discussed increases in the number of strong hurricanes earlier in the chapter,
let us now focus on temperature. A warmer world will, by definition, hold more
thermal energy in the atmosphere and ocean circulation systems. Some of this energy
will become manifest in the form of greater evaporation (hence rainfall) and some in
wind speeds or storm size. Therefore, as the world warms so the frequency of extreme
weather events is likely to increase. Although worldwide ocean evaporation and hence
precipitation are two of the key indicators of global warming, arguably the factor of
greatest psychological impact is the intensity and frequency of heatwaves. These too
are likely to become more intense and frequent as the world warms. For example,
in 2004 Gerald Meehl and Claudia Tebaldi of the National Center for Atmospheric
Research in Boulder, Colorado, published the results of a coupled model together
with field observations to see whether the extreme heatwaves of Chicago and the
south-western area of the Great Lakes (1995) and London/Paris region of Europe
(2003) were unique events or, alternatively, more likely to occur in a greenhouse
future. Their conclusions were that the heatwaves over these parts of the USA and
Europe coincided with a specific atmospheric circulation pattern that is intensified
by ongoing increases in greenhouse gases; this suggests more intense and severe
heatwaves in these regions in the future.