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US VOTERS have delivered their verdict, handing . But how will history judge his performance on climate change – which , but may later come to be seen as the defining issue of our era?

Passing new laws to cut greenhouse gas emissions remains unlikely, with the House of Representatives dominated by climate change sceptics. But Obama has a few key policy levers at his disposal via existing laws – and in his second, and final, term may be less wary of using them.

His best hope is the 1970 . Two landmark Supreme Court rulings, in and , established that it gives the federal Environmental Protection Agency (EPA) the power to regulate greenhouse gases.

Job fears

But with Republican opponents railing against EPA regulations, the Obama administration was cautious about using this power in the run-up to an election dominated by job prospects in a fragile economy.

That may change, suggests , co-director of the Woods Institute for the Environment at Stanford University in California, given that Obama no longer has to worry about getting re-elected: “Most presidents, as they get to their second term, start to think about legacy – what are they going to be remembered for?”

Public opinion may also be shifting in favour of action. The shows that belief in the reality of climate change, and concern about its effects, are at their highest levels since 2008. Significantly, there is growing unease about the link between climate change and extreme weather, with 74 per cent of Americans now agreeing that .

Hurricane Sandy

Having achieved a renewed mandate – albeit by a slender margin in the popular vote – and with the devastation wrought by hurricane Sandy fresh in the memory, Obama may be well placed to seize the moment. “I do think there’s an opportunity, if the president chooses to take it, to show leadership and get attention on the cost that climate change is likely to cause,” says , who heads the US climate initiative of the World Resources Institute in Washington DC.

Regulating US power plant emissions, which account for about , is the top priority. “That’s the biggest opportunity for progress in the next few years,” says , climate policy specialist with the Natural Resources Defense Council in Washington DC.

The EPA has already written draft regulations to limit emissions from , but the main opportunity for big reductions lies with new rules on emissions from existing facilities. According to a recent in Washington DC, cuts of up to 5 per cent from existing plants could keep the US roughly on target to meet to reduce US greenhouse gas releases by 17 per cent by 2020, compared with 2005 levels. How this gets implemented will depend on how the regulations are written but may include improving the efficiency of existing plants or increasing the output of nuclear plants.

Methane leaks

Advocates for cuts also see a chance to curb leaks of methane from natural gas production and distribution pipelines.

In August, the EPA by volatile organic compounds from “fracking” which should, as a by-product, also reduce emissions of methane. Impetus to address methane leaks directly should come from , which aims to put hard numbers on the amount of methane lost across the natural gas supply chain.

Other key decisions include the fate of the , which would pump oil from Canada’s tar sands to refineries in Texas. This will land on Obama’s desk after an environmental review is completed next year.

In his victory speech in Chicago, Obama talked of an America “that isn’t threatened by the destructive power of a warming planet”. So the post-election message is this: forget about new laws to limit climate change, but watch for action nonetheless.