Page 120 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

84 part I The energy–atmosphere System
Decreasing temperature (a) A normal temperature profile.
Decreasing temperature
(b) A temperature inversion in the lower atmosphere prevents the cooler air below the inversion layer from mixing with air above. Pollution is trapped near the ground.
▲Figure 3.7 Normal and inverted temperature profiles. [(c) Bobbé Christopherson.]
(c) The top of an inversion layer is visible in the morning hours over a landscape.
Warmer air Inversion layer
Mixing blocked— pollution trapped beneath inversion
Mixing in the atmosphere
Inversion layer
In 1990, Congress therefore asked the EPA to analyze the overall health, ecological, and economic benefits of the CAA compared with the costs of implementing the law. In response, the EPA’s Office of Policy, Planning, and Evaluation performed an exhaustive cost–benefit analysis and published a report in 1997: The Benefits of the Clean Air Act, 1970 to 1990. The analysis found a 42-to-1 benefit-over-cost ratio and provides a good lesson in cost–benefit analysis, valid to this day.
In December 2009, the EPA enacted an Endanger- ment Finding to guide planning at national, state, and local levels. This finding declares that greenhouse gases “pose a threat to human health and welfare.” However, translating such a significant federal finding into local regulations is challenging.
Although the U.S. legislation improves air quality ir- respective of national borders, there is still no legislation to deal directly with air pollution in Canada. The Canada Clean Air Act was introduced to Parliament in 2006, was greatly debated in Commons Committee, but failed to re- ceive Royal Assent. The Climate Change Accountability Act passed the House of Commons but was defeated at second reading in the Senate in November of 2010.
The Human Denominator, Figure HD 3, presents examples of human–Earth interactions relating to the at- mosphere. As you reflect on this chapter and our modern atmosphere, the treaties to protect stratospheric ozone,
and the benefits from the CAA, you should feel encour- aged. Scientists did the research in the United States, and society made decisions, took action, and reaped enor- mous economic and health benefits. Decades ago scien- tists learned to sustain and protect Astronaut Mark Lee by designing a spacesuit that served as an “atmosphere.” Today, we must learn to sustain and protect Earth’s atmo- sphere to ensure our own survival.
CRiTiCALthinking 3.3 Evaluating Costs and Benefits
in the scientific study The Benefits of the Clean Air Act, 1970 to 1990, the ePa determined that the U.S. Clean air act provided health, social, ecological, and economic benefits 42 times greater than its costs. in 2010 alone, esti- mated benefits exceeded costs at a ratio of 4 to 1. in your opinion, why is the public generally unaware of these de- tails? What are the difficulties in informing the public?
Do you think a similar benefit pattern results from laws such as the Clean Water act, or hazard zoning and planning, or action on global climate change and the endangerment Finding by the ePa? Take a moment and brainstorm recom- mendations for action, education, and public awareness on these issues. What actions can we take in Canada from both a governmental and personal perspective? •
∆6.4 C°/1000 m
Increasing altitude Increasing altitude