The results, the author says, highlight a serious oversight in current cap-and-trade proposals, which make no distinction based on a pollutant's point of origin and provide scientific support for efforts to cut emissions locally.
Domes of increased carbon dioxide concentrations – discovered to form above cities more than a decade ago – cause local temperature increases that in turn increase the amounts of local air pollutants, raising concentrations of health-damaging ground-level ozone, as well as particles in urban air, according to the study.
In modeling the health impacts for the contiguous 48 states, for California and for the Los Angeles area, Mark Jacobson, an engineer at Stanford University, determined that an increase in the death rate from air pollution for all three regions compared to what the rate would be if no local carbon dioxide were being emitted.
The cap-and-trade proposal passed by the U.S. House of Representatives in June 2009 puts a limit on the amount of greenhouse gases that each type of utility, manufacturer or other emitter is allowed to produce. It also puts a price tag on each ton of emissions, which emitters will have to pay to the federal government.
If the bill passes the Senate intact, it will allow emitters to freely trade or sell their allowances among themselves, regardless of where the pollution is emitted.
With that logic, the proposal prices a ton of CO2 emitted in the middle of the sparsely populated Great Plains, for example, the same as a ton emitted in Los Angeles, where the population is dense and the air quality already poor.
"The cap-and-trade proposal assumes there is no difference in the impact of carbon dioxide, regardless of where it originates," Said Jacobson. "This study contradicts that assumption."
"It doesn't mean you can never do something like cap and trade," he added. "It just means that you need to consider where the CO2 emissions are occurring."
Current regulations do not address the local impacts of local carbon dioxide emissions. For example, no regulation considers the local air pollution effects of CO2 that would be emitted by a new natural gas power plant. But those effects should be considered.
In addition to the changes he observed in local air pollutants,the study found that there was increased stability of the air column over a city, which slowed the dispersal of pollutants, further adding to the increased pollutant concentrations.
Jacobson estimated an increase in premature mortality of 50 to 100 deaths per year in California and 300 to 1,000 for the contiguous 48 states.
Mark Z. Jacobson, 'Enhancement of Local Air Pollution by Urban CO2 Domes', Environ. Sci. Technol., March 2010; doi: 10.1021/es903018m
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