Estimating Changes in Variability in a Perturbed Climate Using an
Ensemble Approach.
Galina Guentchev, Krerk Piromsopa, and Julie A. Winkler, Department of
Geography, Michigan State University
It is generally assumed that variability will increase in a warmer climate. However, few
studies have explicitly assessed potential changes in variability. In addition, there is no
consensus among climate researchers on how changes in variability should be
evaluated. Most often interannual variability is considered, but synoptic variability (i.e.,
the variation of daily values around the annual cycle) is also important. In this study,
interannual variability, synoptic variability, and total variability (i.e., variation of daily
values including the annual cycle) of maximum and minimum temperature in the Great
Lakes region were estimated for the period 1990-2100 using an ensemble of climate
scenarios based on four General Circulation Models (GCMs). The results indicate that
there is no consistent trend in variability among the suite of scenarios. For some
scenarios, variability decreases with time whereas for others variability either shows little
change or increases with time. In general, those scenarios developed directly from
GCM temperature output exhibit greater differences compared to those developed from
free-atmosphere variables. For most scenarios, variability changes are larger for spring
compared to the other seasons. Variability changes are similar for both maximum and
minimum temperature, although the range of fluctuations among the different scenarios
is larger for maximum temperature. The scenarios suggest little change in synoptic
variability. Changes in interannual variability are somewhat larger, ranging from -1.0oC
to 1.2oC, although the sign of the change is not consistent. In sum, increased
temperature variability for a warmer world is not conclusively evident among this suite of
climate scenarios.
1