The human role in Australia’s ‘angry’ hot summers

The global increase of 0.8°C in average temperatures (over the last century) has increased the frequency and severity of extreme weather. Like other record-busting heatwaves and extremely hot summers, Australia’s 2013 ‘angry’ summer has now been quantitatively linked to anthropogenic climate change. The study’s authors looked at 20 of the latest climate models used globally, and found nine that were best able to take in observed data, and included some models where they used only natural (not man-made) climate changes.

When running their nine models, including just natural, or natural plus man-made, climate changes, they found that human influence raised the likelihood of this extreme summer by at least five times. Furthermore, these summers will be increasingly likely as the planet warms further still. If we are unable to keep global temperatures from rising less than 2°C, and they rise to 4 or 5°C higher, this last ‘angry’ summer will pale in comparison to the corresponding extreme summers. Other studies suggest that by the end of the centuries 65% of all summers will likely by ‘extremely hot’, and that rising CO2 levels may also lead to longer summers.

The ‘angry’ summer happened despite being during a (weak) La Niña period, when conditions should have been – if anything – slightly cooler and wetter in Australia; three quarters of previous hottest summers in Australia had occurred during El Niño. Many days, and months, were record-breakingly hot, as was the whole summer, and it was preceded and followed by additional heatwaves. Catastrophic flooding and devastating bushfires went along with the summer’s extreme weather.