New US President-elect Barack Obama has a lot in his in-tray already and one of the big issues he'll have to tackle is climate change. Under President George W. Bush the US refused to ratify the Kyoto treaty on greenhouse gas, despite being the world's biggest polluter.

So America has a lot of catching up to do on green issues and Obama has already set out some of his environmental plans. He has pledged immediate action to cut greenhouse gases, in what he promises will be a radical break from Bush's environmental policies.

Unlike Bush, Obama is in favour of binding reductions in carbon gas output and an emissions-trading system. And, when it comes to America's energy supply, Obama would consider some limited offshore drilling but wants to focus on biofuels as well as wind and solar power. He has promised $150 billion over 10 years for development.

Many environmentalists, though, claim real progress can only be made through global agreements. Obama has pledged to re-engage the US in international talks and, crucially, he's willing to sign a deal to tackle global warming without India and China initially involved.

That's a big change from Bush's approach and a step activists say is long overdue. Bush had refused to ratify the Kyoto Protocol soon after taking office: the landmark international agreement was designed to cut carbon gases but Bush feared it would damage America's economy and hand an unfair advantage to booming developing countries.

So his administration instead acted to boost business, loosening up environmental laws, such as America's Clean Air Act. The government also pushed for oil drilling in Alaska but was blocked by Congress on conservation grounds. Green lobbyists claim the US has made little progress at federal level over the last eight years.

But some individual states did take their own environmental initiatives. Texas has become the country's biggest wind energy producer. California imposed laws designed to cut greenhouse gas emissions by a quarter by 2020 and New York's famous yellow taxis are set to go green - they're all due to have hybrid engines in four years.

What the green lobbyists want now is action at the national and international level and they'll be holding Barack Obama to his promises. The largest US environmental group, the Sierra Club, had been campaigning on his behalf.