California is beginning the process of considering possible next steps for the State’s climate policy beyond the 2020 emission target mandated in the Global Warming Solutions Act of 2006 (“AB 32”). As it proceeds along this path, it is very important for the State to consider the international, national, and in-state realities and consequences of its actions.Internationally, California’s intent to address global climate change should be considered in the context of three key factors. First, California, currently representing less than one percent of global GHG emissions, an amount that will surely decline with time, itself can do very little directly to address the problem. Meaningful action will require the participation of all major emitting countries, including more meaningful action nationally by the United States. Second, current negotiations are seriously fragmented due to severe challenges reaching consensus. Nations are pursuing domestic policies of greatly varied stringency and credibility. These efforts are less than needed to address the climate problem, in part, due to a basic challenge of the “global commons”: although the costs of actions are incurred by the jurisdiction taking action, the benefits of those actions – the reduced risk of climate change – are spread globally. Third, the Air Resources Board (ARB) has indicated that the State should aim to reduce GHG emissions to 80 percent below 1990 levels, a level of reductions that is consistent with scientific guidance on the actions needed to stabilize atmospheric GHG concentrations if achieved throughout the world. Within the State, the changes in infrastructure, equipment, and behavior that would be needed to meet this 2050 goal would be both broad and deep. The costs to achieve such targets are unknown, given the many technology uncertainties, but would likely be very significant. Thus, pursuing these targets, without reciprocal commitments from other nations, would likely impose large costs without achieving comparable benefits.