THE number of people expected to die in Sydney from extreme heat will triple by the end of the century, a leaked draft report from the Intergovernmental Panel on Climate Change warns.

Another 800,000 people will fall ill year from contaminated food and water - while more than 270,000 homes will be at risk of collapsing into the ocean from rising sea levels.

The unreleased draft of the IPCC's second report also warns that $226 billion worth of coastal assets including homes, rail and road infrastructure are at risk with just a 1.1m rise in sea levels.

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It reveals Australia's southeast is a global climate change "hotspot" with the ocean warming faster than anywhere else on the planet - and set to increase by 10 per cent more than the global average.

media_camera Climate change graphic

Predictions of more extreme heatwaves came as Sydney last week recorded one of its hottest October days on record.

As bushfires raged across the state yesterday, the report warns very high and extreme fire danger days will increase by up to 30 per cent by 2020 - and up to 100 per cent by 2050.

"There is high confidence that increased incidence of fires in southern Australia will increase risk to people, property and infrastructure such as electricity transmission lines," it states.

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The report of the IPCC's Working Group II, to be released in Yokohama, Japan, next March, also singles out the NSW and Queensland governments for revoking or downgrading planning rules which would help communities adapt to changing conditions and prevent damage to infrastructure.

media_camera Our iconic Great Barrier Reef will be at risk as water temperatures fluctuate.

The report of Working Group I was released in Stockholm two weeks ago and contained new data on projected changes to the atmosphere.

It warned global temperatures were on track to rise between 2C and 4C by 2100 without action to reduce greenhouse emissions.

Warming above 2C is considered dangerous, while 4C is considered catastrophic.

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The draft Working Group II AR5 report - obtained by The Daily Telegraph - examines the extent of the impacts of climate change in different regions of the world.

The section on Australasia, co-authored by 45 scientists from Australia, NZ and the US, is more than 100 pages long and reveals what impacts these changes are expected to have on economies, industries, human health and ecosystems.

media_camera Our snowfields could begin to deteriorate.

The projections for Australia include the warning that deaths from heatwaves in Sydney will triple over the next 70 years from 2.5 per 100,000 to 7.4 per 100,000 under a high-emissions scenario.

And the number of days expected to exceed 40C along parts of the NSW coast, including Sydney, will increase to between 10 and 20.

"Projected increases in heatwaves will increase both heat-related deaths and hospitalisations, especially in the elderly, compounded by population growth and aging," the report states.

"A substantial increase in heat-related death was estimated for Sydney ... without adaptation annual heat-related deaths per 100,000 people were projected to increase nearly threefold from 2.5 in 1961-1990 to 7.4 in 2070-2099.

media_camera We can expect more unseasonal and wild weather too.

"The number of hot days when physical labour in the sun becomes dangerous is also projected to increase substantially in Australia by 2070, leading to economic costs from lost productivity, increased hospitalisation and occasional deaths."

For the first time, damage to infrastructure has also been assessed, with the report finding that a sea level rise of 1.1m would affect over $226 billion of assets in Australia, including up to 274,000 residential and 8000 commercial buildings.

"While the magnitude of sea level rise during the 21st century remains uncertain, its persistence over many centuries implies that realization of these risks is only a question of time."