Assessing the impact of climate change on extreme fire weather events over southeastern Australia

摘要

Extreme fire weather events in southeastern Australia are frequently associated withstrong cold fronts moving through the area. A recent study has shown that the 850 hPa temperatureand the magnitude of its gradient over a small region of southeastern Australia provide a simplemeans of discriminating the most extreme cold frontal events during the last 40 yr from reanalysisdata sets. Applying this technique to 10 general circulation models (GCMs) from the Coupled ModelIntercomparison Project and calibrating the temperature gradient and temperature climatology ofeach model's simulation of the climate of the 20th century against the reanalysis climates allows esti-mates of likely changes in frequency of this type of extreme cold front in the middle and end of the21st century. Applying this analysis to the output of 10 GCM simulations of the 21st century, usinglow and high greenhouse gas emissions scenarios, suggests that the frequency of such events willincrease from around 1 event every 2 yr during the late 20th century to around 1 event per year in themiddle of the 21st century and 1 to 2 events per year by the end of the 21st century; however, thereis a great degree of variation between models. In addition to a greater overall increase under the highemissions scenario, the rate at which the increase occurs amplifies during the second half of the cen-tury, whereas under the low emissions scenario the number of extreme cases stabilizes, although stillat a higher rate than that experienced in the late 20th century.