A running mantra through the climate debate is that global warming is global indeed. Now, however, a scientist has found that localized "CO2 domes" could increase urban smog and other air pollution problems.

In a study published in Environmental Science & Technology, Stanford University professor Mark Jacobson estimated that the effect could cause the premature deaths of 50 to 100 people a year in California and 300 to 1,000 for the continental United States. By comparison, anywhere from 50,000 to 100,000 people a year die in air pollution-related deaths.

The finding, he says, could justify a regional or local approach to cutting greenhouse gas emissions.

Nearly all global and national emissions reduction plans operate on the assumption that a ton of CO2 from a coal plant in China or Ohio has the same climate effect as a ton from cars stuck in traffic on the Los Angeles freeway. Instead, he said, the local health effects of those emissions should also be considered.

"For better or worse, there is this local effect of CO2. That does give us scientific basis for controlling CO2 based on its local impact," said Jacobson.

Already, one California environmental coalition has seized on what it has termed the "Jacobson Effect" in its efforts to oppose the construction of new fossil fuel-burning power plants, such as a new natural gas-fired Russell City Energy Center recently permitted in Hayward, Calif.

Calif. environmental groups following up

"It's very rigorous and compelling, to say the least. It's certainly an argument we will use," said Rory Cox, California program director of Pacific Environment and a member of the Local Clean Energy Alliance.

The concept of an urban "CO2 dome" has been known and documented for a decade, Jacobson said. Even though carbon dioxide is a long-lived pollutant that eventually spreads all around the globe, concentrations have been found to be anywhere from 20 to 100 parts per million higher around big cities, where there are many more constantly emitting smokestacks and tailpipes, according to him.

Many studies have linked increased air pollution to rising temperatures, but this is usually discussed in the context of rising global emissions. Jacobson said that no one before has explored how local CO2 emissions might hurt local residents.

Through detailed air modeling, Jacobson discovered that elevated CO2 levels could increase local temperature, change urban water vapor and wind patterns, and stagnate the air column above cities.

The result would be a direct increase in smog-forming ozone and particulate matter concentrations -- and thus an increase in the air pollution death toll -- he found.

MIT climate expert blames other factors

Chein Wang, a Massachusetts Institute of Technology air quality and climate modeler, was a bit skeptical that elevated local CO2 concentrations could substantially increase air pollution risks. Likely a larger influence, he said, is a common urban problem called the "heat island effect," caused when heat-absorbing paved surfaces and rooftops turn cities into saunas.

"The idea is there, but whether it matters quantitatively, I'm not sure. The urban heat island effect is also a big driver," he said.

Jacobson first began studying the issue when former U.S. EPA Administrator Stephen Johnson denied California a waiver it needed to begin regulating tailpipe emissions of CO2 on its own. Johnson argued that California's actions alone to slow global warming would not lead to any appreciable air quality improvements in the notoriously polluted state.

Since taking office, EPA's current Administrator, Lisa Jackson, has granted California the waiver, and Jacobson said the agency cited his research as a factor in its decision.

"Not all carbon dioxide emissions are equal," said Jacobson, a professor of civil and environmental engineering. "As in real estate, location matters."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500