The climate link to big fires

The climate link to big fires

27 February 2007

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Australia — With recent big fires, there has been much talk about a possiblelink between climate change and the extent and magnitude of bushfires. Has thedrought been to blame for a build up of fuels? Would big fires be brought undercontrol more readily with natural and more regular rainfall?

Dr Nicholls is Professorial Fellow for the School of Geography andEnvironmental Science at Monash University, Lead Author of the Chapter “Understandingand attributing climate change” of the Intergovernmental Panel on ClimateChange (IPCC) Fourth Assessment and a former member of the Australian Bureau ofMeteorology Research Centre.

“The world has warmed,” warned Dr Nicholls, “and has warmedconsiderably in the last 150 years and particularly in the last 50 years.”

Graphs illustrated the observed temperature, a line which curved sharply upwardstowards the end of the last century, a blue band represented the climate modelas calculated when only natural forces, such as changes in solar conditions,volcanic and cloud activity were introduced. This band stayed fairly level overthe timeline. Finally, a red band was shown as the predicted model whenanthropogenic forces were introduced, which rose in tandem with the actualobserved temperature data.

“There is a strong relationship between climatevariations and area burnt in fires.”

What does this mean for fires? Preliminary research on Tasmania Dr Nichollshas conducted in co-operation with the Bureau of Meteorology as a part of theBushfire CRC shows the relationship between rainfall and temperature variationsand the area of land burnt in a fire. This data showed that since 1950 there hasbeen a general trend for a reduction in rainfall to lead to larger areas beingburnt if you have a dry October to March and less area burnt during times ofyear when the rainfall has been increasing. “There is a strong relationshipbetween climate variations and area burnt in fires.” Data presented alsoshows a trend in Victoria that the warmer the year, the greater the area burnt.Dr Nicholls has also concluded from his research that dryer conditions earlierin the year correlates to and earlier start to the bushfire season.

“In the last 10 years the situation has changed,” he said, “becausetemperatures have increased, it appears to mean that fires are starting earlierno matter what the rainfall is.”

So what does this mean for the future? According to the IPCC predictions,Australia is expected to experience a slight rise in temperature over the nexttwenty to twenty five years from two degrees up to four and a half degreesdependant of the levels of greenhouse gas emissions.

The IPCC also predicts that changes in precipitation levels will result in anincrease in the area of damage, and warmer temperatures will mean a much longerbushfire season as indicated by the Tasmanian and Victorian data.

In conclusion, Dr Nicholls stated, “Every drought seems to be hotter thanthe last drought and that has to have implications to fuel management and fuelreduction, as well as to fire response”

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