You might have missed this in the Gillard vs Rudd rumble in the jungle, but earlier today President Obama outlined a wide range of actions to tackle climate change.
In the USA the conservative controlled congress is hostile to any action on climate change, this means that Obama cannot, for example, introduce carbon pricing but he can pursue regulatory action. Hence Obama has chosen to exercise his executive powers at President to reduce US greenhouse gas emissions, forge international action and increase resilience to a changing climate.
You can find a list of the major actions here. One of the more important actions will be using the Environmental Protection Agency to put limits on emissions from new and existing power plants. This will have the effect of either shutting down or forcing the clean up of many coal plants and since coal plants produce a large percentage of greenhouse gas emissions in the USA, this will cause a large decrease to emissions in the long run.
Other actions include higher standards for appliances and buildings so they use less energy and for trucks so they use less fuel. More renewable energy production on the vast amounts of land owned by the US federal government will also be encouraged etc. etc.
Overall, while not as effective or efficient as carbon pricing, Obama's actions make it possible for the US will meet it's targets for reducing greenhouse gas emissions and therefore help to limit global warming.