What may prove to be one of the most important events in human history is scheduled to take place next December in Copenhagen, when the world's leaders gather to address global climate change. Building on the fragile foundation of the Kyoto Protocol, their goal is to plan how to reduce global carbon emissions through 2020. Given what we now know about the science of global warming, this is probably our last significant chance to reduce emissions so as to avoid environmental catastrophe.

So, what should we be doing between now and December 2009, to ensure the best possible outcome for the Copenhagen talks? The answer begins here in the United States.

As the world's largest economy and second-largest source of greenhouse gases (GHGs), there will never be a global plan to address emissions without active U.S. participation and leadership. And for us to have a seat at the table, let alone lead the process, we must be able to show that we are taking our responsibilities seriously and have begun the hard work of reducing our emissions. In other words, by December 2009, we need to have taken some serious steps to reduce our emissions, or recently elected Barack Obama goes to Copenhagen as nothing more than President George W. Bush with better intentions.