摘要：We present an analysis of the barriers and opportunities for incorporating air
quality co-benefits into climate policy assessments. It is well known that many
strategies for reducing greenhouse gas emissions also decrease emissions of
health-damaging air pollutants and precursor species, including particulate matter,
nitrogen oxides, and sulfur dioxide. In a survey of previous studies we found a
range of estimates for the air quality co-benefits of climate change mitigation of
$2- 196/tCO2 with a
mean of $49/tCO2, and the highest co-benefits found in developing countries. These values, although of a
similar order of magnitude to abatement cost estimates, are only rarely included
in integrated assessments of climate policy. Full inclusion of these co-benefits
would have pervasive implications for climate policy in areas including: optimal
policy stringency, overall costs, distributional effects, robustness to discount rates,
incentives for international cooperation, and the value of adaptation, forests, and
climate engineering relative to mitigation. Under-valuation results in part from
uncertainty in climatic damages, valuation inconsistency, and institutional barriers.
Because policy debates are framed in terms of cost minimization, policy makers are
unlikely to fully value air quality co-benefits unless they can be compared on an
equivalent basis with the benefits of avoided climatic damages. While air quality
co-benefits have been prominently portrayed as a hedge against uncertainty in the
benefits of climate change abatement, this assessment finds that full inclusion of
co-benefits depends on—rather than substitutes for—better valuation of climate
damages.
