Local and state regulators have new ammunition in the fight to justify expensive air pollution rules: Cutting smog and soot has an immediate impact on climate change.
A study published last week bolsters the link between air quality and climate, finding that across-the-board cuts in air pollution can spur "substantial, simultaneous improvement" in local air quality and near-term mitigation of climate change.
Trimming smog and soot also represents an alternate and far more immediate global warming solution for regulators stymied by the complexities of other greenhouse gases such as carbon dioxide, said Drew Shindell, a climate scientist at NASA's Goddard Institute for Space Sciences and the lead author of the study.
Tackling air pollution can buy 20 to 30 years worth of mitigation, he said—time that will be needed, if ongoing debates in Poznan, Brussels and Washington D.C. offer any indication—to cut the political and economic knots associated with carbon dioxide.
The health benefits also make a strong case for action to countries that have so far resisted climate mitigation for its own sake. These pollutants—soot, ozone, and smog-causing volatile organic compounds and nitrogen oxides—have well-documented effects on human health. Trimming emissions produces easily quantifiable benefits.
"This is no substitute for targeting carbon dioxide, which in the long run is the main contributor" to climate change, Shindell said. "But if you want to have any effect in the near-term, ... the short-lived pollutants can have very large impacts."
The climate-warming effects of these short-lived pollutants have largely been ignored by scientists and regulators focusing on climate policy. Carbon dioxide, with a lifetime of many centuries, is the star of that show, and the effects on climate by these other pollutants, which endure for mere months, are less well understood.
Regulators also have no way to quantify—as they must when making public health rules—the cost and benefit of climate mitigation. It's impossible to put a cost, for instance, on averting global temperature rise by a few thousandths or even hundredths of a degree.
Still, a collective focus on limiting these pollutants could substantially affect 21st century climate. Several climate models, Shindell and his colleagues showed in a study published last Monday in the journal Atmospheric Chemistry and Physics, suggest that reducing air pollutants in both North America and Asia can produce an immediate cooling effect on climate—certainly far faster than any action on longer-lived emissions like carbon dioxide. "It's much, much faster, as fast as it could possibly be," Shindell said.
Regulators are noticing. President-elect Barack Obama's transition team on Thursday got briefed on emissions and climate and is exploring what tools federal agencies need to better mitigate impacts, said Ellen Baum, a senior scientist with Clean Air Task Force, a Boston-based non-profit that has spent years trying to link climate and urban pollution.
On Thursday California approved the most aggressive plan in the nation to slash greenhouse gas emissions and meet state climate targets. Regulators continue that work today, voting to force 1 million big rig owners to clean up diesel exhaust. Both state rules carry climate and health benefits.