The 15th Conference of the Parties (COP15) sounds like a contradiction in terms--conferences are business-like and dull while parties are, well, fun! But COP 15 is actually the formal name of the annual gathering of nations that participate in the UN's effort to curb climate change and the "party" is about half a year from now in Denmark. Will the US arrive with little more than a tourist map of Copenhagen and some well-worn stories about China being the world's leading emitter of greenhouse gases (GHGs)? In my view, the US will surprise everyone and arrive with the suitcase full of robust climate policies, but if the UN insists on sticking to its formula for a new global climate deal, based on the Kyoto Protocol, the Americans won't be the only ones departing empty handed. The divisions between developed and developing nations, especially the US and China, are too old and too real to solve with a broad one-size-fits-all agreement. Instead, we may need a series of mini-deals, each tackling specific sources of GHGs (by geography and industrial sector), which taken together creates a mosaic that completes a more detailed, practical picture. The good news is that these various agreements are already being drafted, signed, and implemented. For example, at last year's Governors' Global Climate Summit in California, US states reached agreements with states in Brazil and Indonesia that will preserve rainforests, thereby cutting GHGs instead of trees. In another example, US states and Canadian provinces have invited China to help design a massive international cap-and-trade system to use markets to reduce GHGS and ensure that projects are sustainable and verifiable. Other sub-national governments--usually with US climate leadership states in the mix--are signing agreements to reduce GHGs with measures like energy efficiency R&D and other policy initiatives that pave the way for their respective national governments to get deals done when they convene in meetings like the COP15. People forget that the US signed the Kyoto Protocol in 1992--but never ratified it. That's because when policy makers looked inward, they had no idea how to achieve what had just agreed to and, as a result, there was no political support for ratification. Today the opposite is true--33 states have "climate action plans" that put them on a par with Kyoto signatories, showing the feds how we can slash GHGs--and the politics that usually undermine well-meaning aspirations and agreements. So let's prepare to party hearty in Denmark in December. The US will bring a lot of its own policies and programs that are already effectively reducing GHGs, albeit at the state and regional level--in many cases, with international partners already lined up. If the UN builds on this foundation, along with the great work that many Kyoto signatories have done in their countries so far, there will be more than funny hats and confetti on the floor when this party’s over.