In the absence of a geo-engineering miracle, the world's climate problem cannot be solved by one large country or a limited group of countries. A substantial effort by all major emitters is needed. A coordinated international effort is essential to promote vigorous efforts by all parties and to avoid causing competitive imbalances through climate policies. However, the appropriate degree of homogeneity among policy approaches across countries at the current time is debatable. Although a uniform price on carbon would promote a cost-minimizing solution to the global climate problem, capacities and responsibilities differ across countries, as do the potential impacts of climate change. In the absence of a common, top-down approach, considerable progress could nevertheless be made through decentralized, national programs that are increasingly linked and harmonized, over time.