come countries and are directly related to a country’s actions to reduce its own GHG emissions.


Policies to limit the magnitude of climate change may offer direct ancillary benefits such as reducing the emission of air pollutants and lowering dependence on imported petroleum fuels. The use of offsets as a climate policy may have indirect but beneficial effects on forestry and agricultural practices. In principle, climate change limiting policies should be designed to capitalize on these benefits, but applying this principle systematically is difficult in practice, because estimates of ancillary benefits are uncertain and the benefits, costs, and potential for leakage are often project- and location-specific. Nevertheless, ancillary benefits may be robust enough to justify influencing national climate policy in a few areas, including the following:

  • To accelerate the reduction of oil use in the transportation sector. The combined costs of oil consumption impacts on U.S. energy security and human health (as estimated by recent studies discussed in this section) is roughly equivalent to 45-55 cents per gallon of gasoline (which can be converted to roughly $45-55 per ton of CO2). Policy strategies for actually realizing energy security and health benefits from reducing oil use requires more thorough analysis than is presented here, but the possible benefit is large enough to warrant attention.

  • To capture the full benefit of emissions-limiting actions, especially in low- and middle-income countries. Although there is considerable variation among countries, ancillary benefits associated with reducing air pollution and improving forestry and agricultural practices can be particularly large in low- and middle-income countries.

  • To reduce emissions of methane, short-lived pollutants, and HFCs. Methane, other precursors for tropospheric ozone, and black carbon aerosols lead to adverse human health effects on broad regional scales. HFCs, used as replacements for stratospheric ozone-depleting refrigerant agents, are potent GHGs.

  • To encourage climate policy actions that result in closure or upgrading of electric power plants with disproportionately large health impacts. This applies primarily to power plants that lack effective air pollution controls and are located near densely populated areas.

These potential co-benefits provide additional impetus for pursuing several of the key actions suggested elsewhere in this report, including, for instance, the reduction of oil use in the transportation sector; the strategies for engaging middle- and low-income

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