Garnaut. Today. 12.30pm eastern time

"More than a year in the making and some 550 pages long"

Ahead of today's release of the long-awaited draft Garnaut report on climate change one of Australia's top economists has warned that it risks delivering “the worst of both worlds”.

More than a year in the making and some 550 pages long, the report was commissioned by Labor's leader Kevin Rudd when in opposition in partnership with Australia's eight state and territory Labor governments.

Although modeled on Britain's Stern Report, it will break new ground by examining the implications of climate change for a single nation rather than for the globe.

Among the risks facing Australia that it will examine are a virtual end to irrigated agriculture in the Murray Darling Basin, an end to snow-based tourism and thousands of extra heat-based deaths per year.

The report will outline a framework to guide the design of an Australian emissions trading scheme and a system by which its targets can be ratcheted up as other nations adopt similar schemes...

Although the report will not contain recommendations, its author, the Professor Ross Garnaut told the Canberra Times last night that its views about the best design of the scheme would be clear.

The draft report will canvass neither the size of the necessary emission reduction target nor the cost of archiving that target.

That discussion will await the results of Treasury modeling due in August. The final Garnaut Report will be released in September.

Today's launch of the report at the National Press Club will be followed by a series of five town hall meetings in each of Australia's roadshow mainland capitals next week.

The following week, on Wednesday July 16, the Climate Change Minister Penny Wong will release a green paper at the Press Club outlining the Government's thinking.

She has been keen to stress that the government will reach its decisions independently of the Garnaut Review, saying the green paper will outline its “thinking on these issues, informed by a range of matters, including Professor Garnaut's report, including advice from within the Government and, of course, including the consultations with business, with industry that Government has been undertaking”.

At the Australian National University yesterday one of Professor Garnaut's colleagues, Professor Warwick McKibbin made an impassioned plea for the government to reject what he understood to be central feature of the scheme to be put forward in the Garnaut Report.

Professor Garnaut has spoken in favour of a so-called “cap and trade” emissions trading scheme, under which a cap would be placed on total greenhouse gas emissions and the number of tradable permits strictly limited in order to bring it about.

Professor McKibbin told a public lecture at the ANU yesterday that only a “very very brave politician” would adopt such a scheme without “some form of safety valve”.

It could lead to wild fluctuations in the price of permits, leading to political pressure to water down the target.

“It would be like committing to a carbon tax but without knowing what the tax rate would be,” he said. “It would be the worst of both worlds”.

Professor McKibbin is instead pushing for a model similar to that proposed by the previous Prime Minister's task force in which an unlimited number of extra permits would be available from the government at a fixed price in order to prevent the market price climbing too high.

“It might be that there will be no problem. It might be that the carbon price remains very low, and there's no need for a safety valve. But that's relying on a lot of maybes,” he told the ANU audience.