1 November 2017
Analysis of a recently developed dataset of weather conditions that influence fire activity (i.e. fire weather conditions) has shown a clear link between climate change and bushfire conditions over the past 67 years, including a trend to more dangerous fire weather conditions in some regions.
For the first time, this study allowed fire weather conditions to be examined throughout Australia based on a long period of observations. It examined maps of the Forest Fire Danger Index (FFDI) – a measure that takes in temperature, humidity, wind speed and rainfall – throughout Australia. Higher FFDI values indicate more dangerous conditions for bushfires.
What did the study find?
A new ‘normal’: changes in average conditions
Increases in average FFDI values for spring and summer show that fire weather conditions in southern Australia have become increasingly more dangerous in recent decades.
More frequent extremes
Due to the long record of data examined in this study, changes in the occurrence of extremes could also be examined. (Extremes are by definition relatively rare events at a given location, so they may not always show up in short-term records.) Over the study period, extreme fire weather has also become more frequent, with more frequent extremes observed for some seasons and regions of Australia.
As well as looking at when extremes occur, the nature of the dataset means that researchers could also look at where the extreme FFDI values occur. This spatial information is important for planning, insurance and climate adaptation.
Longer fire seasons
The time of the year when higher FFDI values typically occur has also changed over the past 67 years, with the start of the fire season getting earlier in southern Australia. This early start does not have a corresponding earlier end, so the period of time with dangerous fire weather conditions has expanded.
Why is it so?
The increased severity of fire weather conditions is attributable at least in part to anthropogenic climate change, including in relation to increasing temperatures. In particular, it is well established that observed daily maximum temperature for Australia has increased by about 1.0 °C since the year 1910, with a large amount of this increase occurring during the second half of the 20th century due to anthropogenic greenhouse gas emissions.
Planning for the future
While the focus of this study was to understand fire weather conditions that we’ve already experienced, there are a number of ways the results are helping with planning for the future:
- The fire weather patterns over space and time that have been identified in this study will feed into decision-making by fire authorities, other emergency services and planning agencies – they can base their planning for future fires on the timing and return period of extreme conditions, as well as on the locations where these conditions occurred.
- The relationship of the El Niño–Southern Oscillation (ENSO) to fire weather was demonstrated in this study, with the results highlighting opportunities for the development of long-range (weeks to seasons) fire weather forecasts – we already have the ability to predict ENSO up to several months in advance, so using the relationship of fire weather to ENSO to provide forewarning of severe fire weather is certainly feasible.
- The data used for this analysis can be used as a historical benchmark that will be useful in assessing the performance of climate models – the better a model simulates conditions we’ve already observed, the more confidence we can have in its projections of the future climate.
For more detail, please refer to the original research paper:
Dowdy A. 2017. Climatological variability of fire weather in Australia. Journal of Applied Meteorology and Climatology, doi:10.1175/JAMC-D-17-0167.1.