Climate change futures: health, ecological and economic dimensions

Table 1.1 Extreme Weather Events and Projected Changes
Source: IPCC 2001
While the amount of rain over the US has increased
7% over the past century, that increase camouflages
more dramatic changes in the way this increased precipitation
has been delivered. Heavy events (over 2
inches/day) have increased 14% and very heavy
events (over 4 inches/day) have increased 20%
(Groisman et al. 2004). The increased rate of heavy
precipitation events is explained in great part by the
tropical ocean surfaces (Curry et al. 2003) along with
a heated atmosphere. The frequency and intensity of
extremes are projected to increase in the coming
decades (Houghton et al. 2001; Meehl and Tebaldi
2004; ABI 2005) (see Table 1.1).
Recent analysis of tropical cyclones (Emanuel 2005;
Webster et al. 2005) found that their destructive
power (a function of storm duration and peak winds)
had more than doubled since the 1970s, and the frequency
of large and powerful storms had increased,
and that these changes correlated with ocean warming.
Changes in the variance and strength of weather
patterns accompanying global warming will most likely
have far greater health and ecological consequences
than will the warming itself.
Examples abound of the costs of weather anomalies.
The most recent series of extremes occurred in the sum-
mer of 2005. In July, a heat wave, anomalous in its
intensity, duration and geographic extent, enveloped
the US and southern Europe. In the US particularly,
records were exceeded in numerous cities. Phoenix,
AZ experienced temperatures over 100°F for 39 consecutive
days, while the mercury reached 129°F in
Death Valley, CA. Drought turned a large swath of
southern Europe into a tinderbox and when it ended
with torrential rains, flooding besieged central and
southern parts of the continent and killed scores.
OUTLIERS AND NOVEL EVENTS
Beyond extremes, there are outliers, events greater
than two or three standard deviations from the average
that are literally off the charts. A symptom of an
intensified climate system is that the extraordinary
becomes more ordinary. We have already experienced
major outlier events: the 2003 summer
European heat wave was one such event—with temperatures
a full six standard deviations from the norm.
This event is addressed in depth in this report.
For developing nations, such truly exceptional events
leave scars that retard development for years. It took
years for Honduras to rebuild infrastructure damaged
in the 1998 Hurricane Mitch, for example.
19 | THE CLIMATE CONTEXT TODAY