1480. Australia Drying Caused by Greenhouse Gases, Study Shows

By Science Daily, July 13, 2014

The agreement between observed and model simulated 

rainfall changes supports the idea that human activity contributed 

to the drying of southwestern Australia and that the drying will
increase in the 21st century. Changes in fall-winter rainfall from
observations (top panel) as compared to model simulation of
the past century (middle panel), and a model projection of
the middle of the 21st century. Photo: Graphic by NOAA's
Geophysical Fluid Dynamics Laboratory

NOAA scientists have developed a new high-resolution climate model that shows southwestern Australia's long-term decline in fall and winter rainfall is caused by increases in humanmade greenhouse gas emissions and ozone depletion, according to research published today in Nature Geoscience.

"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 humanmade climate drivers, scientists showed that the decline in rainfall is primarily a response to humanmade increases in greenhouse gases as well as a thinning of the ozone caused by humanmade 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."

Story Source:
The above story is based on materials provided by NOAA Headquarters. Note: Materials may be edited for content and length.

Journal Reference:

1. Thomas L. Delworth & Fanrong Zeng. Regional rainfall decline in Australia attributed to anthropogenic greenhouse gases and ozone levels. Nature Geoscience, July 2014 DOI: 10.1038/ngeo2201