IN A WORLD THAT DEMANDS simple solutions for complex problems, it is easy to look at the Copenhagen climate talks as a disappointment or even a disaster. There was a hope among many, and even an expectation among some, that 193 nations would sign a treaty reconciling a huge list of divided interests: developed versus developing economies, transparency versus sovereignty, existing technology versus emerging technology, and so on.

The talks were chaotic and the worst organized conference I've ever attended. But at least part of that chaos ensued from the fact that so many people wanted to attend and so many governments wanted to be in the room for the dealing.

Forget the emissions targets calculated in percentages and the offers of aid calculated in dollars. The single most important number to come out of Copenhagen is 115. That's the final count on the number of heads of state who came. The number at Kyoto, the site of the last comparable meeting 12 years ago, was exactly one.

I recognize that much needs to be done quickly. I am convinced by the scientific consensus on the risks we face from climate change. And I understand the impatience of those who started raising these concerns twenty years ago.

But a gathering of virtually all of the world's leaders to act on a challenge based on science is a stunning event. Has such a gathering ever happened except in the aftermath of a cataclysmic war? That human beings can for the first time in history gather to respond to science is both a testament to the scientific evidence itself and to the ability of humans to avert suicide.

There was another observation to be made in Copenhagen. Climate change is as much about competition as it is about cooperation. To some degree, the biggest divide in Copenhagen was between those who feel markets are the key to addressing the challenge and those who feel that governments are the key.

I left Copenhagen more convinced than ever that, while governments have a critical role, only markets are the mechanism powerful enough to reallocate the resources needed to transition from a carbon-intensive to a low and no-carbon economy.

One reason this is true is admittedly brutal: some governments (and the people they represent) are going to win in this transition and some will lose. In a nutshell, this is why competition rather than cooperation will drive climate mitigation and adaption.

Thomas Friedman of the New York Times writes brilliantly of the competitive challenge facing the United States. But this argument applies even more to cities and regions, especially those like Philadelphia whose assets are rising in value in a carbon-constrained world.

Smart cities and regions understand that sustainability is an economic development strategy not an environmental strategy. City and regional governments can identify and nurture the conditions under which markets can exploit, yes exploit, opportunities created by climate change.

For cities, sustainability is about poverty reduction not carbon reduction. It's about prosperity not polar bears. It's about attracting resources on the basis of return-on-investment not need.

For regions, sustainability is about investing in an energy infrastructure that raises the competitive value of certain locations by lowering their energy profile. It's about deploying energy efficiency and ecosystems services within watersheds, foodsheds, commutersheds, and energysheds that operate at a regional scale.

Copenhagen mattered because governments got in a room and saw just how big this market is going to be. Philadelphia continues to announce city and regional green projects every week. That's raising capital in political and financial markets that will help us win the coming competition.

Mark Alan Hughes teaches at PennDesign and the TC Chan Center for Energy Studies.