New report shows global warming link to Australia's worst drought
SYDNEY: A new scientific report by WWF-Australia and leading meteorologists has shown that human-induced global warming was a key factor in the severity of the 2002 drought. The report compares the 2002 drought with the four other major droughts since 1950 and has found higher temperatures caused a marked increase in evaporation rates from soil, watercourses and vegetation.
The report, Global Warming Contributes to Australia's Worst Drought, warns that higher temperatures and drier conditions have created greater bushfire danger than previous droughts. Drought severity also has increased in the Murray Darling Basin, which produces 40% of Australia's agricultural product.
The report states that in 2002 Australia recorded its highest-ever average March-Nov daytime maximum temperature, with the temperature across Australia 1.6°C higher than the long term average and 0.8°C higher than the previous record. The Murray Darling Basin experienced average maximum temperatures more than 1.2°C higher than in any previous drought since 1950.
"The higher temperatures experienced throughout Australia last year are part of a national warming trend over the past 50 years which cannot be explained by natural climate variability alone," said Professor David Karoly, formerly Professor of Meteorology at Monash University, who co-authored the report with Dr James Risbey from Monash University's School of Mathematical Sciences and Anna Reynolds, WWF-Australia's Climate Change Campaign manager.
"Most of this warming is likely due to the increase in greenhouse gases in the atmosphere from human acitivity such as burning fossil fuels for electricity and transport and from landclearing."
Professor Karoly said the actual trend in Australian temperature since 1950 was now matching the climate model studies of how temperatures respond to increased greenhouse gases in the atmosphere.
"This is the first drought in Australia where the impact of human-induced global warming can be clearly observed," he said.
Dr James Risbey said that although the 2002 drought was related to natural climate variations associated with El Niño, the higher temperatures could not be attributed solely to this factor.
"While higher temperatures are expected during El Niño triggered droughts, the 2002 drought temperatures are extraordinary when compared to the four major droughts since 1950, with average maximum temperatures more than 1°C higher than these other droughts," he said.
The report contains new data on evaporation rates and says low rainfall and higher evaporation has adversely impacted on agricultural productivity with lower crop production leading to lower export earnings for farmers.
"Global warming is a reality that is affecting the livelihoods of rural Australians and Prime Minister Howard must act to prevent further economic and environmental devastation," said Anna Reynolds, WWF-Australia's Climate Change Campaign manager.
"We can slow global warming, keep temperature increases to the lower end of the scale and reduce the severity of future droughts. The Kyoto Protocol is the first international agreement with targets for reducing greenhouse gas emissions and slowing global warming - it is in our national interest to ratify the treaty."
Print quality graphs can be accessed at htttp://www.maths.monash.edu.au/~ris/drought.shtml