emissions. Finally, whereas incentives and subsidies to develop cleaner technologies maybe be slow and costly, they can complement other emissions-reduction policies.
International agreements and policies, to be effective, need to be enforced, verified, and monitored. Standards and certification mechanisms for reducing GHG emissions also need to be created and implemented. Constraints to monitoring compliance with and the effectiveness of such policies include lack of adequate and reliable methods for measuring GHG emissions, lack of mechanisms for accurately accounting for GHG emissions and for offsets, and lack of technical capacity to monitor and enforce policies nationally and across international borders.
Benefit-cost analyses seek to translate climate change impacts, including lost or gained ecosystem services, into a monetary metric so that they can be compared to estimates of the costs and benefits associated with policies to limit the magnitude or adapt to the impacts of climate change. Alternatively, cost-effectiveness analysis is often used when the costs and benefits of action differ greatly in character, or when the benefits are subject to greater uncertainty or controversy. Cost-effectiveness analysis allows analytically based comparisons of decisions without requiring that all impacts—in this case, damages from climate change and costs of emissions reduction—be reduced to a single metric. Both approaches can be powerful tools for informing decisions, but disagreements about (1) how to value ecosystem services or other resources for which market prices do not exist; (2) how to handle low-probability-high-consequence events, discount rates, and risk aversion; (3) prospects for technological innovation; and (4) how to incorporate distributional and intergenerational equity concerns lead to wide ranges in estimates of the social value of climate actions.
Effective climate policy making requires analyses that consider the complexity of real policies, how institutions interact across levels of government from global to local, and equity issues. Climate policies are not made in a vacuum. They interact with other climate and nonclimate policies and are often nested across different scales from local to global. In the United States, rapidly emerging local and state climate policy agen-