Angry summer shaped by a shifting climate

Will Steffen, Australian Climate Commissioner,  Executive Director of the ANU Climate Change Institute at Australian National University

The Conversation, 4 March 2013

The hottest summer on record. The hottest month on record. The hottest day ever recorded for the whole of Australia. Heatwaves, bushfires, record rainfall and floods – extreme events across the land. This was the angry summer.

The Climate Commission's latest report, The Angry Summer, assesses the events of this summer and the influence of climate change on them.

Australia is a land of "droughts and flooding rains". Our history is defined by extreme events. Black Friday in 1939, Cyclone Tracy in 1974, Ash Wednesday in 1983, Black Saturday in 2009 and the terrible floods of the last few years – disasters are etched into the Australian psyche. The angry summer continues this history of extremes.

The angry summer is unusual for the record-breaking intensity and duration of the weather events. The season began with one of the driest periods on record from July to December. The heatwave in late December 2012 and the first weeks of January 2013 was unusually long and widespread. During this heat event more than 70% of Australia experienced extreme temperatures at some stage. The hot, dry weather contributed to dangerous bushfire conditions in many parts of Australia.

Later in the summer, parts of Queensland and New South Wales experienced record-breaking heavy rainfall, with daily rainfall of more than 400 millimetres in many locations. This rainfall produced severe flooding along the coast of Queensland and northern New South Wales.

All weather is influenced by climate change. The climate system is warmer and moister than it was 50 years ago, and this influences the nature, impact and intensity of extreme weather events. All of the extreme weather events of the angry summer occurred in a climate system that has vastly more heat compared to 50 years ago. That means that they were all influenced to some extent by a climate that is fundamentally shifting.

The average temperature in Australia has risen by 0.9°C since 1910. The change in average temperature has greater impacts at the margins of the temperature scale. It is highly likely that extreme hot weather will become more frequent and severe in Australia over the coming decades. Australia's angry summer shows that climate change is already adversely affecting Australians.

Looking towards the future, it is virtually certain that extreme hot weather will continue to become even more frequent and severe around the globe, including Australia, over the coming decades. It is also likely that the frequency of heavy rainfall will increase over many areas of the globe.

In Australia and around the world we need to take urgent action to reduce greenhouse gas emissions. The preventative action we take now and in the coming years will greatly influence the extent of climate change in the future, and therefore the severity of extreme weather events that our children and grandchildren will have to cope with.

This is the critical decade to get on with the job.