Heatwaves in Australia are becoming more frequent, are increasing in intensity and are lasting longer, according to an interim report by the Climate Council.
The report, which will be released in full in February, finds that climate change is having a key influence on a trend that has seen the number of hot days in Australia double and the duration and frequency of heatwaves increase in the period between 1971 and 2008.
South-eastern Australia has baked in extreme temperatures this week, with Melbourne set for four consecutive days over 40C – a run not replicated since 1908. Adelaide is due to go one further and have five days over 40C, with Thursday's forecast of 46C threatening to break city's record temperature of 46.1C.
The Climate Council, a privately run group of climate scientists and economists who previously formed the government-funded Climate Commission, defines a heatwave to be at least three consecutive days at a temperature in the top 10% for that time of year.
Its interim report states there will still be record cold events but that these events are being eclipsed by record hot events by a ratio of three to one. Heatwave frequency in Australia will "increase significantly" in the future, the report warns.
"As greenhouse gases continue to accumulate in the atmosphere from the burning of fossil fuels, more heat is trapped in the lower atmosphere," the report states. "This increases the likelihood that hot weather will occur and that heatwaves will become longer and more intense.
"It is crucial that communities, emergency services, health and medical services and other authorities prepare for the increases that are already occurring in the severity and frequency of many types of extreme weather.
"The south-east of Australia, including many of our largest population centres, stands out as being at increased risk from many extreme weather events – including heatwaves."
Dr Sarah Perkins, report co-author and research fellow at the UNSW, told Guardian Australia that the current heatwave was happening during a "neutral" period of climatic variability.
Before the 2009 Black Saturday fires, there was a decade-long drought, which produced some climatic variability reasons behind it," she said.
"This year, we aren't in an El Niño, we're in a neutral pattern, so we might expect some extreme weather but not this hot scorching weather. Last year was a neutral year too, on the back of a strong La Niña, and we still got extreme weather.
"I'm not discounting natural variability, but there is still the background signal of climate change. The high-pressure system probably would've happened anyway, but climate change is exacerbating these events.
"While we can't blame climate change for any one event, we can certainly see its fingerprint. This is another link in the chain."
Perkins said her latest work had analysed heatwave trends up to 2013. She said the trend "just gets worse – it's a bit scary really".
"We are experiencing between one to three extra heatwave days a year, compared to the long term average, which doesn't sound a lot but it doesn't need many of these days to kill people or cause damage," she said.
"And this is with background warming of 1C. If current trends continue and we get to 4C warming, it will be a whole lot worse than now."
Perkins' fellow report author Will Steffen said the increase in heatwaves would have a wide range of impacts on the way Australians live.
"Heatwaves have significant impacts on our health, our infrastructure, our agriculture and our ecosystems," he said.
"It is essential that we understand the influence of climate change on heatwaves to ensure that health services, transport providers, farmers and the community are prepared for what is happening now and what will happen increasingly in the future.
"Australia has always had hot weather. However, climate change is loading the dice toward more extreme hot weather."
The Greens have cited the heatwave in an attack on Tony Abbott's climate change policies, calling for him to abandon plans to dismantle the carbon pricing system.
"The Climate Council has warned that global warming will bring more extreme weather and heatwaves and we can't pretend it's not going to happen," said the Greens senator Lee Rhiannon. "We must prepare for it and stop it getting worse by reducing greenhouse pollution.
"The clean energy laws are already reducing greenhouse pollution and creating jobs. It really is time for Tony Abbott to abandon his ideological rejection of the climate science and put the Australian community first."
The Department of Environment has been contacted for its response to the report.