Hours after promising in Berlin that action was coming on climate change, Barack Obama is preparing to make what could be the biggest environmental move of his presidency. White House officials say the President is planning to implement new regulations that would significantly reduce carbon emissions on existing power plants. The plan —which was hinted at in The Los Angeles Times earlier this week — involves instituting new rules through the Environmental Protection Agency, which doesn't require the approval of Congress. 

Even with the Executive Branch doing all the heavy lifting, implementing new EPA regulations is a lengthy and complicated process, and one the administration must begin soon if the President hopes to accomplish his goal before leaving office. Reports say that Obama is essentially giving up on the idea that Congress will pass any sort of climate legislation in the next few years (Republicans are already holding up the nomination of his new EPA director), but a 2007 Supreme Court ruling gives him the authority to write new rules for power plants that have already been built. Almost 40 percent of greenhouse gas emissions in the U.S. come from traditional, mostly coal-fired, electricity plants. Reining them in (if successful) could become a major building block of Obama's legacy.

Earlier on Wednesday, Obama made climate change a key section of his address at the Brandenburg Gate in Berlin, calling it "the global threat of our time." Adding that "Peace with justice means refusing to condemn our children to a harsher, less hospitable planet," the President suggested he was ready to take "bold action" on the matter. Experts say the new power plant rules are the biggest step that he can take on his own, without needing Congress or the courts, though whatever he comes up with is sure to be challenged by businesses and some state governments. The plan could also include new rules on energy efficiency of appliances and construction projects, and a new push on renewable energy sources.