Australia's record-breaking autumn heat is just a taste of what's to come if we continue to lag behind global powers who are moving away from fossil fuels to combat climate change.

Environmental experts have warned Australia will continue to experience record-breaking heat and extreme weather in the wake of a damning report that reveals a notable climb in average temperatures across the country at the start of March.

Former Australian of the Year, the Climate Council's Tim Flannery, said conditions over the past few months had been unprecedented, and inaction from Australia following a global agreement in Paris to do more was "quite disgraceful".

"We've had three months in Australia where nothing has happened, but we got the announcement that emissions from the burning of fossil fuels have grown," he said.

State and federal governments must take action, with policies to remove sources of pollution and build cleaner energy systems, Professor Flannery said.

Climate Council chief executive Amanda McKenzie says March's unseasonably warm spells show Australia is now experiencing the consequences of climate change.

Average global temperatures could be four to six degrees warmer by the end of the century if nothing is done, Ms McKenzie said.

"That is something we just don't want to imagine," she told reporters after the launch of the Climate Council's report, Heat Marches On, on Sunday.

"At the moment we're not even at one degree warming globally and we've seen such huge changes."

The CEO says Australia continues to lag behind other countries when it comes to investment in alternative energy sources and the scaling down of traditional fossil fuels despite our naturally sunny and windy conditions.

"It's something that we should be excelling at, and we should be showing the world how it's done. But we're not," Ms McKenzie said.

"If you look at what's happening globally, the US for instance has got a moratorium on new coal mines.

"Countries like China, Germany are pushing ahead in renewable energy. The world is taking off."

Climate change has already begun to affect Australia's tourism sector, with widespread coral bleaching in the Great Barrier Reef, triggered by elevated sea surface temperatures.

Environment Minister Greg Hunt on Sunday upgraded the coral bleaching threat level after flying over the reef to observe some of the hardest hit areas around Lizard Island, north of Cairns.

"As you go north of Lizard Island, it becomes more severe," he told reporters.

The extent of the damage has prompted Mr Hunt to increase the coral bleaching threat from level two to level three.

"That means we are moving to immediately increasing monitoring, and that's being coupled with action that is being taken," the minister said.

The revised bleaching level comes almost a week after the Great Barrier Reef Marine Park Authority raised the coral bleaching warning from level one to level two after widespread bleaching was detected.

HOW WE'RE SWELTERING:

* Max temps at least 4C above average, from March 1 to 4

* Temps 8 to 12C above average for most of southeast

* Record 39 straight days over 26C in Sydney

* Perth had more 40C days this summer than ever before

* Melbourne had hottest March night on record, at peak of 38.6C

* Canberra had 10 straight days of 30C or more

* Echuca, VIC, and Tocumwal, NSW, sweltered through eight straight days of 38C or more in March, breaking records for any month of the year

* Temperature records shattered around the world, with this January and February hotter than any other

(Source: Climate Council)