The report from the national government’s scientific agency predicts a grim future for Australia’s largest and best-known city, concluding that climate change is inevitable and the city should start immediate planning.

The CSIRO predicts the average Sydney temperature will rise 4.8 Celsius (40 degrees Fahrenheit), well above the average 3.0 predicted globally by the UN Intergovernmental Panel on Climate Change.

Rainfall is forecast to fall by 40 percent and the number of heat-related deaths in the city of four million is expected to soar almost 800 percent from the current 176 to 1,312 by 2050.

The report said a 20 centimetre (7.9 inch) rise in sea levels would result in storm surges of 22 metres on Sydney’s beaches, leaving them eroded and inundating sea-side homes.

The heat is expected to whip up 24 percent more wind storms and fuel almost double the number of severe bushfires in the state of New South Wales.

State Premier Morris Iemma, who commissioned the CSIRO report, said the national and state governments needed to act to ensure the city’s future.

“This might sound like a doomsday scenario but it’s one we must confront,” Iemma, from the Labor party, said.

“We don’t need to be waiting for the impact, it’s real and it’s here.”

He criticised the federal Coalition government for refusing to sign up to the Kyoto protocol on reducing greenhouse gas emissions, calling for a national summit to address the issue of climate change.

Prime Minister John Howard and his close ally, US President George W. Bush, lead the two developed countries that have refused to ratify the UN protocol.

Climate change and the scarcity of water are shaping as key battlegrounds in the upcoming national election between Howard’s Coalition and the main opposition Labor party.

Australia, already the world’s driest inhabited continent, is struggling with its worst drought in more than a century.

Report author and CSIRO researcher Ben Preston said there was no doubt climate change was occurring and that, unlike previous historical shifts, mankind was driving the change.

“What’s important for people to understand is that this is not simply a lot of hand waving, there’s quite a bit of scientific research and effort both within Australia and internationally that goes into producing these estimates,” he told public radio.

“The problem there is that future climate change is already built into the system, so the warming we’ve been experiencing in recent years is really a function of greenhouse gases we emitted a few decades ago.”

Preston said change was inevitable but long-term planning could help Australia cope.

“Australia has demonstrated in the past that it has quite a significant capacity to cope with rainfall, water scarcity and pretty significant rainfall variability but maintaining a healthy and sustainable water supply over the future independence of climate change is obviously going to require some considerable reforms in terms of how we use water and how we price water,” he said.