Before the Democrats took control of Congress in 2006 and the White House in 2008, US climate strategists focused much of their energy at state and local level. Their goal was threefold: to test new climate policies, to reduce greenhouse-gas emissions where possible and to increase pressure on businesses and policy-makers to craft a viable national compromise. The third strand of that strategy failed this year, making the successes attained in the other two all the more important. From this perspective, the vital environmental vote of last week's midterm elections was in California, which forcefully rejected the ballot aiming to scuttle the state's pioneering climate law, Proposition 23.

Sixty-one per cent of California voters weighed in against Proposition 23, which put forward short-sighted arguments that the state's drive to reduce greenhouse-gas emissions would hobble an already struggling economy. Current law requires the state to cut greenhouse-gas emissions by 25% on 1990 levels by 2020, and the California Air Resources Board is bringing in regulations to make that happen, including a cap-and-trade system that would allow businesses to decide where to make emissions reductions. California has long led the United States on environmental policy, and this is exactly the kind of action that will expand and could, in time, pave the way for a more comprehensive approach on climate in Washington DC.

As policy labs of long standing, US states can demonstrate the power of 'bottom-up' leadership.

California has already been joined by seven other states in the country's west, and four Canadian provinces, in the Western Climate Initiative. Farther east, six states and one Canadian province have signed the Midwestern Greenhouse Gas Reduction Accord. These two programmes aim to cut greenhouse-gas emissions by 15% and 20%, respectively, on 2005 levels by 2020. Carbon trading has already begun under the first such programme, the Regional Greenhouse Gas Initiative, under which ten northeastern states have committed to reducing current levels of emissions by 10% by 2018.

In total, 23 US states and five Canadian provinces have begun their own climate initiatives, independent of their countries' federal governments. The Washington DC-based World Resources Institute calculates that these initiatives cover half the US population and one-third of its greenhouse-gas emissions. In Canada, the numbers are even more impressive: more than three-quarters of the population and half the greenhouse-gas emissions are covered. Twenty-eight states have standards on renewable energy, and countless other efforts are under way that would encourage energy savings and greenhouse-gas reductions at the state and local level.

And do not count out the federal government just yet. The administration of President Barack Obama is preparing to roll out new greenhouse-gas regulations next year and has a variety of other tools at its disposal. The administration has ordered the federal government, the largest energy consumer in the nation, to reduce emissions by 28% on 2008 levels by 2020. The federal government — and the defence department in particular — also has enormous purchasing power. If used wisely, that could help drive green technologies to market.

Clearly, these limited efforts are not sufficient. Concerned citizens in the United States and around the world are right to be disappointed in the lack of leadership and vision in Congress. Barring a sharp reversal on their campaign rhetoric, it seems that the situation will only get worse when Republicans take control of the House of Representatives next year. But many of these Republicans hail from those states that are quietly embarking on their own programmes to combat global warming. These aren't just feel-good measures, either. They are confidence builders.

It's possible that, globally, climate change is simply too complex a problem for a comprehensive top-down solution. There are too many interests at stake, too many losers with loud voices. And although most Americans clearly accept the reality of global warming, most people simply don't care that much, particularly when economic woes loom large. That's not a recipe for success in the power corridors of Washington. But California and other US states are policy labs of long standing, and as such will continue to demonstrate the power of 'bottom-up' leadership.