Challenges of the 21st Century - Science For Environmental Protection: The Road Ahead - page 23

The agency's efforts to improve air quality continue to have high priority
despite decades of progress because the economic costs that air pollution im-
poses on society remain high. For example, Hidden Costs of Energy: Unpriced
Consequences of Energy Production and Use (NRC 2010) estimated that the
aggregate damages in the United States associated with air pollution from the
country's coal-fired power plants were at least $62 billion in 2005 and that air
pollution from motor vehicles contributed at least another $56 billion in dam-
ages. The Clean Air Act is an expensive law in terms of compliance, but it still
has a highly positive benefit-to-cost ratio (EPA 2011d). EPA recently issued a
report called The Benefits and Costs of the Clean Air Act from 1990 to 2020
(EPA 2011d) . According to that study, the direct benefits from the 1990 Clean
Air Act amendments are estimated to be almost $2 trillion by the year 2020,
exceeding costs by a factor of more than 30 to 1.
Impacts of Climate Change
In the last several decades, it has become clear that human activities have
had substantial effects on global climate. The global temperature has increased
by an average of 0.6 o C since 1901 (IPCC 2007) and variability has increased as
well, especially in patterns of precipitation and runoff. That pattern led Milly et
al. (2008) to conclude that “stationarity is dead” 1 in the context of water-
resource management and to suggest that a new paradigm is needed for dealing
with the fact that human society can no longer count on the conformity of mean
precipitation—or even variability in annual precipitation—to historic patterns.
Many climatologists, while concerned about the increase in mean global tem-
perature, are focused on the changes in extreme temperatures and precipitation
(such as floods and droughts) because the extremes cause greater social and eco-
logic disruption than a shift in average temperatures. Climate change may be the
most obvious example of the need for systems thinking in policy-making, given
complex interactions between regional air quality and climate change and the
numerous pathways by which the environment and human health can be influ-
enced. Many of the factors discussed earlier in this chapter will have direct and
indirect influences on climate change, which will itself influence land use pat-
terns and other drivers.
There is evidence that the climate change that has occurred in recent dec-
ades has made it harder and more expensive to address air-quality problems
(see, for example, Bloomer et al. 2009 and IWGSCC 2010). Furthermore, there
is strong scientific consensus that in coming decades climate change is likely to
increase the frequency of heat waves, exacerbate problems with water supply
and water quality, increase the severity of storms, and disrupt ecosystems, habi-
1 Stationarity is the term used when statistics (such as mean, median, variance) are
constant through time.