From correspondents in Washington, United States, 03:31 PM IST

It is not about science, and it is not about any moral imperative. But the US Supreme Court's decision to tackle global warming for the first time is expected to have far-reaching and lasting consequences for US policy.

The question argued before them Wednesday is technical: does the government's Environmental Protection Agency (EPA) have the authority, or even an obligation, to set limits on greenhouse gas emissions based on a 16-year-old law passed by Congress on air pollution?

An alliance of 12 states, three cities, 14 environmental groups, a number of businesses and a ski resort argued that it does. But an equally imposing coalition of 10 states, nine automakers, utility companies and businesses are backing the EPA's claim that it has no such authority.

The case hinges on whether carbon dioxide - a natural gas that in large, man-made amounts is blamed by most scientists for raising the earth's temperature - can be considered an air pollutant under the 1990 Clean Air Act, and must therefore be regulated due to its harmful impact on public health.

The Bush administration acknowledges that global warming is happening and is in part man-made, but has so far stood by voluntary caps on emissions and refused to set mandatory limits, on account of their negative impact on the economy.

The US has also remained outside the Kyoto Protocols, an international agreement that sets targets on each participating country for reducing carbon dioxide emissions. The US contributes about 25 percent of the world's greenhouse gases.

Congress has so far been unwilling to approve mandatory caps on greenhouse gas emissions, whether from cars or power plants - an oddity given that the current court case hinges on a law passed by that very same institution.

Environmental groups recognise the shortcomings of their approach, but maintain it is the only way to spur action.

'Regulating global warming through litigation is the least effective way to do so, but we are just not willing to wait any longer,' said Josh Dorner of the Sierra Club.

'Even if we lose, this simply is going to increase the pressure on Congress to act,' Dorner said.

In contrast to the federal level, 11 states across the country are poised to adopt stringent emissions standards on new models from carmakers - an authority they also claim to derive from the Clean Air Act and which could potentially be quashed by the Supreme Court.

Though the case revolves on a technical issue, the justices seemed acutely aware of its importance. Justice Anthony Kennedy, who many expect will be the deciding voice on the court, said he was doubtful of a 'reassuring statement that we need not decide about global warming in this case'.

Some analysts have speculated the court will take a middle ground - authorising but not obliging the EPA to act, and thereby allowing the state laws to go ahead. A decision is expected by July.

(Staff Writer, © IANS)