International considerations. America’s climate choices affect and are affected by the global dimensions of climate change. U.S. emissions reductions alone will not be adequate to avert dangerous climate change risks; rather, our emission reductions must be accompanied by comparable actions from all other major emitters. U.S. climate policies can potentially have a major effect on the actions other countries take, and this potential represents another important criterion for evaluating domestic response options. In general, domestic policies that help leverage broader international-scale efforts (for example, cooperative research and development programs in clean energy technology) can be expected to reduce overall climate risk more than policies that affect U.S. emissions alone. Similarly, in comparing the advantages and disadvantages of different policy options for reducing U.S. GHG emissions (e.g., cap-and-trade programs, carbon taxes, regulatory approaches), each should be considered in the context of how they link domestic policies to global efforts.

Robustness. Given the uncertainties inherent in predicting future climate change and its impacts, as well as the difficulty of predicting technological, social, and economic developments, there is a great strategic advantage in pursuing response options that can perform well under a wide range of possible futures. For instance, sound risk management in the agricultural sector may include investing in the development of crop varieties that are resilient to a wide range of temperature and precipitation conditions. As another example, market-based regimes offer an advantage over industry-specific performance standards because the former approach has a higher likelihood of continued effectiveness under varying future economic or technological conditions.23

When the likelihood of different future outcomes is not well known, pursuing multiple options (i.e., a portfolio approach) and other “hedging” strategies can help ensure a robust response. For example, it would be prudent to invest in multiple new energy technologies to meet future needs because the ultimate success of any one new technology is always uncertain. As another example, it is prudent to design the infrastructure for transportation, water, and utilities to withstand a range of weather extremes including intense rainfall, flooding, and drought scenarios. Ensuring robustness may also include strengthening general adaptive capacity through early warning systems and disaster response preparations.

The degree to which any particular policy option meets the different criteria listed above depends not only on the type of policy but also its scope and stringency. For example, an overly weak auto fuel efficiency standard may be cheap and politically feasible but not very effective in reducing climate-related risks, whereas an overly tough standard may promise high levels of risk reduction but be very expensive, pose significant equity concerns, and be difficult to implement successfully.

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