For the first time in 12 years, the Democrats have control of the House of Representatives and the Senate. The shift has significant implications for US climate policy.
One notable change is that Californian Democrat Barbara Boxer has replaced the Republican Senator of Oklahoma, James Inhofe, as chairman of the Senate’s Environment Committee.
Mr Inhofe has a track record of blocking Bills to control greenhouse gases, and once famously described climate change as "the greatest hoax ever perpetrated on the American people."
Ms Boxer, in contrast has championed environmental issues since she entered the senate in 1992. She has promised to introduce legislation to tackle climate change along the lines of California’s new Global Warming Solutions Act, which commits the state to bring emissions down to 1990 levels by 2020 (ENDS Report 380, pp 34-37 ).
The election results prompted Senators John McCain - a front runner for the Republican presidential nomination - and Independent Joe Lieberman to reintroduce the Climate Stewardship and Innovation Bill. This would bring US emissions back to 2004 levels by 2012 and to 1990 levels by 2020. The Bill is co-sponsored by Democrat presidential hopeful Barack Obama.
The political swing has also had an impact on local climate initiatives. In Massachusetts, Democrat Deval Patrick replaced Republican Governor Mitt Romney. Mr Patrick has promised the state will rejoin the regional greenhouse gas initiative (RGGI), where seven other north eastern states have joined in a cap and trade scheme to control emissions from power generation.
Meanwhile, California and the other RGGI members have discussed linking the scheme with a Californian version. California is already working with Oregon, Washington and New Mexico to set up a west coast trading scheme.
In the last six months, around 100 mayors have joined a coalition of cities that have voluntarily taken on emissions reduction targets equivalent to the rejected US Kyoto target. So far 358 mayors representing more than 55 million Americans have signed up to the initiative.
The Supreme Court has been drawn into the action. In December, it began hearing a case brought by California and 11 other states to force the Environmental Protection Agency to control greenhouse gas emissions.
Meanwhile, the Bush administration is being forced to respond to growing public awareness of the effects of climate change. In December, it proposed listing polar bears as a "threatened" species because melting arctic sea ice is reducing its habitat. Under the Endangered Species Act, the US government can not authorise any action which might threaten the habitat of an endangered species. However, it is unclear whether the polar bear’s new status will have any effect on US climate policy.
Further clues to the Bush administration’s intentions will emerge when the President makes his State of the Union address at the end of January.