Speaker: Dr. Francis Zw iers\, Director\, Pacific Climate Impacts Consortium
Abstract: T
here is now a well established approach to detecting and
attributing t
he causes of observed changes in mean climatic conditions
that has bee
n applied progressively from global scales to regional
scales to tempe
rature and other climate variables. While this research
has provided a
great deal of useful information about the causes of
climate change o
bserved during the past century or more\, policy makers
and others hav
e also been demanding answers about whether there are
attributable cha
nges in frequency and/or intensity of extreme weather
and climate even
ts. The statistical techniques required to respond to
these questions
are only now begin developed. This talk will describe a
standard techn
ique that is used in climate change detection and
attribution research
\, propose a parallel approach that might be used to
assess whether th
ere is a detectable human influence in the far tails of
the distributi
on of a climate variable such as daily maximum air
temperature\, demon
strate an initial application of the approach\, and
discuss limitation
s and further areas of improvements. Using the
approach that is propos
ed\, we show that an anthropogenic influence is
detectable globally\,
and in many regions\, in the extremes of daily
maximum and minimum tem
peratures. Globally\, waiting times for extreme
annual minimum daily m
inimum and daily maximum temperatures events that
were expected to rec
ur once every 20 years in the 1960s are now
estimated to exceed 35 and
30 years respectively. . In contrast\, waiting
times for circa 1960s
20-year extremes of annual maximum daily minimum
and daily maximum tem
peratures are estimated to have decreased to less
than 10 and 15 years
respectively.