"This new high-resolution
climate model is able to simulate regional-scale precipitation with
considerably improved accuracy compared to previous generation models,"
said Tom Delworth, a research scientist at NOAA's Geophysical Fluid
Dynamics Laboratory in Princeton, N.J., who helped develop the new model
and is co-author of the paper. "This model is a major step forward in
our effort to improve the prediction of regional climate change,
particularly involving water resources."
NOAA researchers
conducted several climate simulations using this global climate model to
study long-term changes in rainfall in various regions across the
globe. One of the most striking signals of change emerged over
Australia, where a long-term decline in fall and winter rainfall has
been observed over parts of southern Australia. Simulating natural and
human-made climate drivers, scientists showed that the decline in
rainfall is primarily a response to human-made increases in greenhouse
gases as well as a thinning of the ozone caused by human-made aerosol
emissions. Several natural causes were tested with the model, including
volcano eruptions and changes in the sun's radiation. But none of these
natural climate drivers reproduced the long-term observed drying,
indicating this trend is due to human activity.
Southern
Australia's decline in rainfall began around 1970 and has increased over
the last four decades. The model projects a continued decline in winter
rainfall throughout the rest of the 21st century, with significant
implications for regional water resources. The drying is most severe
over southwest Australia where the model forecasts a 40 percent decline
in average rainfall by the late 21st century.
"Predicting
potential future changes in water resources, including drought, are an
immense societal challenge," said Delworth. "This new climate model will
help us more accurately and quickly provide resource planners with
environmental intelligence at the regional level. The study of
Australian drought helps to validate this new model, and thus builds
confidence in this model for ongoing studies of North American drought.