The most
important spatial
pattern (top) of
the monthly Palmer
Drought Severity
Index (PDSI) for
1900 to 2002.
The time series
(below) accounts
for most of the
trend in PDSI.
Drought is increasing most places
Mainly decrease in rain over
land in tropics and subtropics,
but enhanced by increased
atmospheric demand with
warming
Trenberth/IPCC
