It is commonly accepted that the root cause behind the recent devastating bushfires in Australia was Climate Change. To be a tad clearer and more precise, when I write “Climate Change” I do not simply mean an unfortunate quite natural climate variation that resulted in a dry season, but that the root cause was us, our fossil fuel emissions are actually responsible. To use the correct full term – did anthropogenic climate change cause the bushfires?
The quick short answer is “Yes”.
The longer answer is that it is indeed possible to attribute what happened to anthropogenic climate change. I do not mean as an opinion, but as a very specific measurable scientific fact.
World Weather Attribution (WWA)
There exists the World Weather Attribution (WWA) partnership. This is an international effort to analyse and communicate the possible influence of climate change on extreme weather events, such as storms, extreme rainfall, heatwaves, cold spells, and droughts.
Their goal is to delivers timely and scientifically reliable information on how extreme weather may be affected by climate change.
The WWA is a partnership of:
- Environmental Change Institute, University of Oxford (ECI)
- Royal Netherlands Meteorological Institute (KNMI)
- Laboratoire des Sciences du Climat et de l’Environment (LSCE)
- University of Princeton
- National Center for Atmospheric Research (NCAR)
- Red Cross Red Crescent Climate Centre (The Climate Centre).
“The goal of this ambitious effort is to use peer reviewed science to provide decision makers, the public, and the media with early, science-based answers to the questions of whether and to what extent global warming caused by greenhouse gas emissions played a role in an event’s probability and magnitude,” said Dr. Friederike Otto, of the ECI. “Our team believes that a careful science-based assessment is extremely valuable, even in cases where we can’t provide hard numbers,” said Dr. Maarten van Aalst, Director of the Red Cross Red Crescent Climate Centre. “It is important to recognize that ‘we don’t know’ or ‘there is no significant trend’ are also valid findings.” This work also helps to answer questions about trends in risk and vulnerability, and the role of human activity in extreme weather.
The Australian Bushfire Attribution study
WWA have published a study that asked this question “whether and to what extent human-induced climate change has altered the likelihood and intensity of fire weather risk in the southeastern Australian bushfires in 2019/2020“.
To tackle this they focused on two key components, extreme high temperatures and lack of rainfall.
They approach was to compute the change in probability of a Fire Weather Index, extreme heat or drought as high as was observed in 2019/20 in the current climate compared to the climate of around 1900 in both observations and climate models.
This is not a simply easy question to address. Here is what they discovered.
- Four climate models for which FWI could be calculated show that the probability of a Fire Weather Index this high has increased by at least 30% since 1900 as a result of anthropogenic climate change. As the trend in extreme heat is one of the main factors behind this increase and the models underestimate the observed trend in heat, the real increase could be much higher. This is also reflected by a larger trend in the Fire Weather Index in the observations.
It is a complicated question.
The study reveals the complexity of the 2019/20 bushfire event, with some, but not all drivers showing an imprint of anthropogenic climate change. So yes, human-caused climate change has indeed had an impact, it made it about 30 percent more likely.
“We’re very sure that is a definite number we can scientifically defend,” said the lead author of the study, Geert Jan van Oldenborgh of the Royal Netherlands Meteorological Institute,referring to the 30 percent figure.
“We think it is much larger than that, but we can’t prove that until we find out why there is this discrepancy between the observations and the climate models.”
Independent Views of the WWA Study
- The WWA Homepage is here
- The WWA summary of their analysis for the Australian Bushfires is here
In the media ..
- The New York Times (4th March 2020) – Climate Change Affected Australia’s Wildfires, Scientists Confirm