The 2009 Copenhagen climate summit may in retrospect prove a critical turning point in the evolution of the international climate change effort. For a decade and a half, the principal aim under the U.N. Framework Convention on Climate Change (UNFCCC) had been to establish, and then to extend, a legally-binding regime regulating greenhouse gas (GHG) emissions. Despite late efforts to temper hopes for Copenhagen, the general expectation was that the summit would carry forward this process by producing a legally-binding outcome. The result, instead, was the Copenhagen Accord, a non-binding agreement that captured political consensus on a number of core issues but in the end was not formally adopted by the official Conference of the Parties (COP).

Copenhagen’s “failure” has led many in and outside governments to begin rethinking the best way to mobilize an effective international response to climate change. To be certain, many parties remain fully committed to achieving new legally-binding commitments as quickly as possible; some are looking to do so at the 17th Conference of Parties (COP-17) to be held in 2011 in South Africa, or at Rio+20, the summit to be held in 2012 to commemorate the 20th anniversary of the Earth Summit in Rio de Janeiro. But many others are coming to believe that the path to a new legally-binding agreement will be longer and more incremental. In this view, the process of constructing a post-2012 international climate architecture will involve a gradual process of evolution.

An evolutionary path is, in fact, quite common in multilateral regime-building. While the progression of every regime is unique, reflecting its particular policy needs and political constraints, broad patterns can be seen. Few regimes spring forth wholly formed. Generally, they grow over time, becoming broader, deeper and more fully integrated as parties gain confidence in one another, and in the regime itself.

What a more incremental approach would imply in the case of climate change is not necessarily clear, however. Short of a legally-binding agreement, what types of international arrangements are most urgent or effective? Which of these can or should be pursued through the UNFCCC and which might be more productively pursued in other international forums? Is it critical that we know now the form of legally-binding agreement we aspire to—must it, for instance, include the Kyoto Protocol—or can that unfold over time?

This paper starts to explore these and related issues. It argues that a comprehensive and binding global agreement has strong virtues, and should be the ultimate goal, but that in working toward that end, parties should focus their efforts for now on concrete, incremental steps both within and outside the UNFCCC. The paper proceeds as follows: First, it examines why international regimes often evolve gradually over time, rather than emerging all at once. Next, it unpacks the various dimensions along which international regimes evolve. Then, it examines how the climate change regime has evolved to date. Finally, it outlines several different lines along which the climate change regime might evolve in the future.

Of course, an evolutionary process is by definition gradual and will take time. Given the urgency of addressing climate change, there is no guarantee that this process will reduce emissions quickly enough to avert catastrophic climate change. If a more rapid process were possible, it would be worth pursuing. The paper does not argue that an evolutionary approach is best; rather, it concludes that, at present, an evolutionary process is politically the most promising way forward.