Bushfire Weather in Southeast Australia: Recent Trends and Proj

Bushfires are an inevitable occurrence in Australia. With more than 800 endemic species, Australian vegetation is dominated by fire-adapted eucalypts. Fire is most common over the tropical savannas of the north, where some parts of the land burn on an annual basis. However, the southeast, where the majority of the population resides, is susceptible to large wildfires that threaten life and property. A unique factor in these fires of the southeast is the climate of the region. The southeast experiences a so-called Mediterranean climate, with hot, dry summers and mild, wet winters. The winter and spring rains allow fuel growth, while the dry summers allow fire danger to build. This normal risk is exacerbated by periodic droughts that occur as a part of natural interannual climate variability. Climate change projections indicate that southeastern Australia is likely to become hotter and drier in future. A study conducted in 2005 examined the potential impacts of climate change on fire-weather at 17 sites in southeast Australia. It found that the number of 'very high' and 'extreme' fire danger days could increase by 4-25% by 2020 and 15-70% by 2050. Tasmania was an exception, showing little increase. This report updates the findings of the 2005 study. A wider range of observations is analysed, with additional sites in New South Wales, South Australia and southeast Queensland included. The baseline dates of the study, commencing in 1973, are extended to include the 2006-07 fire season. The estimated effects of climate change by 2020 and 2050 are recalculated using updated global warming projections from the Intergovernmental Panel on Climate Change (IPCC). Two new fire danger categories are considered: 'very extreme' and 'catastrophic'. This study also differs from the 2005 study in that different analysis methods are used. In addition to the annual changes in fire danger estimated before, changes to individual seasons and season lengths are explicitly examined. There is also a focus on the changes to the upper extremes of fire danger. These projected changes are compared with trends over the past few decades. The primary source of data for this study is the standard observations made by the Bureau of Meteorology. The locations of the 26 selected observing stations are shown in Figure E1. At these stations, the historical record of Forest Fire Danger index (FFDI) and the likely impacts of future climate change are calculated. There are homogenization issues with the data that could …