Fire risk has risen across Australia over the past four decades, particularly in the south and southeast, in a clear example of man-made climate change, according to one of the world’s foremost climate experts.

A NSW report studying changes in Australia’s “fire weather” – conditions that are likely to lead to a fire outbreak – between 1973 and 2010 has found an upward risk trend across most of Australia, and a particularly strong trend in SA, western NSW, Victoria and northern Tasmania.

Melbourne and Adelaide recorded 49% increases in their cumulative annual Forest Fire Danger Index (FFDI), a scale used to quantify fire weather conditions by state agencies to announce fire warnings.

Professor David Karoly, lead author for the Intergovernmental Panel on Climate Change and a Professor of Climate Science at Melbourne University, says while the report doesn’t link rising fire risk with climate change, its findings are consistent with other papers that demonstrate a connection.

He says that as the La Nina weather pattern dissipates, marked by above average rainfall, fire risk would likely rise over the next few years.

Professor Karoly was not involved in the latest report but has undertaken similar research investigating fire weather trends in the late ’90s and early 2000s.

“My work looked at what would happen to fire risk if climate change took place, but this study has said, well, the fire risk across much of Australia and especially in the southeastern parts of Australia has increased on average,” he said.

“The longer-term trends are consistent with human-caused climate change.”

The report analyses temperature, relative humidity, wind speed and rainfall trends at 38 locations across Australia over a 37-year period. Sixteen locations showed major increases in fire risk, while none recorded a significant decrease.

The report also finds the fire season is now longer, with the FFDI rising in spring and autumn.

While an increased FFDI does not necessarily lead to more fire outbreaks, the report notes Victoria’s Black Saturday bushfires in 2009 “were driven by some of the highest FFDI values on record, against a background of severe drought conditions in the preceding months and years”.

Initially released in April this year and published by the UK’s Royal Meteorological Society, the report has not been publicised by the NSW Government and its authors have not been able to comment given its sensitive findings.

The report is jointly authored by the NSW Office of Environment and Heritage, the University of NSW and the Centre for Australian Weather and Climate Research, a joint partnership between the Bureau of Meteorology and CSIRO.

Also see ANALYSIS