Developments in the US Congress last week exposed the thinly-veiled trickery embedded in the Rudd Government’s revamped Climate Pollution Reduction Scheme.

In a large step towards adopting global warming legislation, the House Energy and Commerce Committee approved the American Clean Energy and Security Act (ACES).

The “Waxman-Markey” bill would cap US emissions at 17% below 2005 levels by 2020, which translates into around 4% below 1990 levels. The Rudd Government has made adoption of a 25% cut in Australia’s emissions by 2020 conditional on advanced countries committing in Copenhagen to emission cuts “at least 25% below 1990 levels”.

The US position predictably falls a long way short of the conditions set by the Government on 4th May for an Australian 25% reduction target. It even falls well short of the conditions set by Mr Rudd for Australia to adopt a 15% target.

The gap between 4% and 25% is unbridgeable. If ACES becomes law it is impossible to imagine the US Congress revisiting the policy after Copenhagen and increasing the cap from 17% to the 38% needed as a condition for the 25% Australian target.

It was always going to be a 5% target; the only surprise is that anyone believed otherwise.

After one of the most intense lobbying efforts in US history, the 930-page set of measures, although significantly watered down, still represent a quantum leap in the US response to climate change. Within the bounds of normal politics a 17% cut is as much as one could hope for. But the scientific warnings have taken us beyond normal politics.

Democrats from coal states — known as “brown dogs” — were the obstacle to the original Waxman-Markey target of 20%. In a series of intense meetings their support was bought by the bill’s co-sponsor, Henry Waxman, who doled out billions of dollars in free emission allowances.

Although Barack Obama had called for 100% auctioning of allowances during the presidential campaign, the price of getting the bill through the Committee was the sacrifice of 85% of the allowances, albeit with some promised as compensation for low-income households.

To the consternation of some environmentalists, ACES would trump the Supreme Court’s decision that carbon dioxide is a pollutant by denying the Environmental Protection Authority the power to regulate emissions under the Clean Air Act, a prospect that chilled some big polluters and led them to support Waxman-Markey as a lesser evil.

The legislation has some huge loopholes that could severely erode its effectiveness. In particular, it allows polluters to meet their obligations by investing in forest protection in developing countries.

Allowing “offshore compliance” could sharply reduce pressure on the energy sector to invest in low-carbon infrastructure at home, especially as the law allows for up to two billion tonnes of offsets, more than the emission reductions required. The 17% emission reduction could be achieved without any decline in domestic US emissions.

Loopholes big enough to drive a Hummer through and a target that falls well short of what the scientists are calling for have not deterred some of the mainstream environmental groups from supporting the Waxman-Markey bill, but others like Greenpeace and Friends of the Earth have refused to play the trade-off game.

And there are senior environmentalists upset that President Obama did not use his public influence to push for tougher climate legislation. His advisers are said to have told him that if he put his authority on the line and lost, his ability to push through health reforms would be weakened.