Summer was hottest ever: report - Brisbane Times

AAP

As he toured Queensland meeting people mopping up after January's devastating floods, Climate Commissioner Will Steffen faced the same question again and again.

It was: "Why, just after cleaning up from one flood, am I getting hit with another?"

People didn't understand why the supposedly one-in-100-year floods were happening so frequently, but they did know something wasn't right.

The floods were one part of what Professor Steffen described as a "very, very unusual summer" that included catastrophic bushfires, damaging rain and the most intense heatwave on record.

In his Climate Commission report, Angry Summer, released on Monday, Prof Steffen concludes the extreme weather of 2012/13 was climate change in action, and more events are on the way.

"We've been storing extra heat in this system for about a century now, due to increasing greenhouse gases," he told AAP.

"When we do the sums, as we do in the climate models, for the next couple of decades you're going to see increasing likelihood of very hot weather and more record hot weather."

That means wilder weather than last summer, when a staggering 123 records were broken throughout Australia in 90 days.

It was the hottest summer, capped by the longest and most extreme heatwave on record. Sydney, Newcastle and Hobart sweltered through their hottest days on record. The average temperature in Australia was 40.3C on January 7.

Rainfall records were smashed along eastern Australia, tropical cyclones wreaked havoc, bushfires raged in every state and territory and tornadoes hit Bundaberg.

Prof Steffen acknowledges Australia has always had extreme weather.

But he argues the way these events are shifting "tells a very, very compelling story" because extreme weather events are occurring in a climate system that is warmer and moister than it was 50 years ago.

Prof Steffen said action taken now to cut greenhouse gas emissions would have a big influence on how hot it would be in the second half of the century.

Climate Commissioner Professor Tim Flannery argues the events of summer didn't happen out of the blue and were forecast decades ago by scientists warning of the dangers of man-made climate change.

"As these record-breaking conditions continue, it gets ever more difficult to deny there is a link between them and human activity," he said.

Recent news China would cap its coal use by 2015 was a "real landmark" and should give other nations the confidence to curb their own emissions more than ever before.