One of the most important environmental cases in years will today come before the United States Supreme Court. In Massachusetts vs the Environmental Protection Agency, an alliance of American states will contend that the Federal Clean Air Act compels the EPA to consider greenhouse gases as pollutants. If successful, this would require the EPA to regulate the emissions of motor vehicles, something it has been resisting for a number of years.

There would seem to be a strong case against the EPA. The Clean Air Act states that the EPA shall set standards for "any air pollutant" that "may reasonably be anticipated to endanger public health or welfare". Carbon emissions surely fit perfectly into this category. The EPA argues that the individual states have no legal standing because they cannot show that they will be specifically harmed by the agency's failure to regulate greenhouse gases. But the science has progressed. The evidence that climate change will gravely affect all of us on the planet is now overwhelming.

Yet it is still difficult to see this individual case coming to anything. Even if the court rules against the EPA, the agency would still be left to decide on how to go about controlling emissions. While it remains in such a state of denial over the threat posed by climate change, there is little hope that it would rigorously enforce its new powers. Some have also suggested that a ruling in favour of the EPA could jeopardise the efforts of certain states to curb emissions unilaterally.

But the broader picture provides more grounds for encouragement. This case hints at a new direction of attack against the obtuseness of national governments over global warming. Climate change will be presented here as something that will have a detrimental effect on all of our lives. While many Americans are instinctively suspicious of restrictions imposed by the federal government, most tend to be in favour of action to preserve their local environment. The key is to link what is a global crisis with local politics.

Also, the fact that this case is getting a hearing in court entrenches the principle that climate change is the overarching crisis of our time. Legal action is establishing itself as another outlet for pressure on our governments to act. In a country as litigious as America, this is no small consideration. The state of California is presently suing the world's largest car manufacturers, arguing that their vehicles have caused it billions of dollars in environmental damage.

The battleground is broadening. And those who would deny their responsibility for safeguarding the future of the planet have never looked so isolated.