Don't be fooled by wet summer - scientists
- From: AAP
- March 15, 2012
CLIMATE scientists say Australians shouldn't be fooled into thinking the world isn't warming just because much of the country experienced a relatively wet and cool summer.
The years 2010 and 2011 set a record of 1409mm of rain averaged over Australia. That tops the previous two-year high set in 1973 and 1974.
The global average temperature for 2011 was also lower than all but two of the years between 2000 and 2010.
But a new report from the government's climate commission warns that it's wrong to be blinded to the long-term trend of global warming by year-to-year variability.
What's more, the recent heavy rainfall and flooding could actually have been caused by climate change.
"Climate change cannot be ruled out as a factor in recent heavy rainfall events," the commission states in its report, released today.
"The sea surface temperatures (SSTs) around northern Australia during the spring and early summer of 2010 to 2011 were the highest on record," the report said.
"This has very likely contributed to the exceptionally heavy rainfall over much of Australia in the last two years."
La Nina years - which tend to be wetter and cooler in eastern Australia - typically bring high SSTs to northern Australia. But warming over the past century is also a contributing factor.
Higher SSTs drive higher rates of evaporation from the ocean and thus provide more water in the atmosphere for rainstorms.
As for the slightly lower global average temperature in 2011, the report points out that 2011 was still warmer than all but one of the years in the 20th century.
And it was the warmest La Nina year on record.
"Focusing on just the La Nina years over the past four decades the long-term warming trend stands out strongly," the report states.
The climate commission also stresses that most of the record rainfall over the past two years came during spring and summer. The normal rainfall season runs from April to November.
"Averaged from 1970, and even just the past 15 years, the southeast and southwest, Tasmania and the southeast Queensland coast (still) show an overall drying trend," the report states.
"The wetter conditions experienced in southeastern Australia in the last two years are consistent with scientists' knowledge and understanding of how the climate is changing in the long term."
Looking forward, the commission says extended dry periods are expected to increase by the end of the century for much of Australia with an increased risk of drought.
When long, dry periods are interrupted by welcome periods of wet weather the rain is more likely to fall as heavy downpours rather than extended drizzle.
What does all this mean for government?
The climate commission, established by Labor to spruik the case for tackling dangerous climate change, concludes: "We need to do our part along with other countries to drive rapid and deep reductions in the emission of greenhouse gases."
The report was written by climate commissioner Will Steffen, University of NSW academic Matthew England and meteorology professor David Karoly.