The issue of global warming throws off more ideological heat than scientific light or economic insight. Five years after the first Earth Summit in Rio de Janeiro, what we don't know is still a multiple of what we do know. The science is better but not good enough. The good intentions of well-meaning people notwithstanding, caution and not crisis should guide U.S. policy in reducing greenhouse gases. The U.S. should not ignore the potential harm from global warming but it must act pragmatically, not emotionally.
What do we really know about global warming? Rising temperatures are the only certainty. But how much, how fast, and how important it is are all open to question. Estimates go from 1.8 degrees Fahrenheit to 6.3 over the next century, under current rates of burning coal, gas, and oil. No one knows if rising temperatures will melt the polar ice caps and flood Seattle or just extend the growing season for corn.
What would be the economic impact of curbing global warming? Who knows? Cutting U.S. carbon emissions by 40% by 2020 and returning them to 1990 levels could reduce economic output by 8% or even raise it by 5%, according to the World Resources Institute. It depends on assumptions about alternative fuels, international cooperation, conservation, and curbs on burning fossil fuels.
The only sensible thing for the U.S. to do with these data is take out insurance. The Cassandras in the 1970s were wrong about shrinking natural resources and limits to growth. But this time, the temperature is really rising. What to do? The U.S. has dragged its feet for five years in setting up incentives to reduce carbon dioxide emissions. It's time to act. We'd like to see serious tax breaks for energy efficiency and cleaner air. A sliding scale for state auto registrations, based on emissions, could help get polluting clunkers off the road. Sliding scales on state sales taxes that reward energy-efficient vehicles (including lawn mowers, boats, and planes) could help as well. Let's also experiment with a carbon-trading system for CO2 emissions that emulates the current market for pollution credits. And Detroit should hustle to develop an engine that doubles fuel efficiency. Surely the auto makers don't have to wait for Washington to force them again.
The science on global warming is improving. Now should be the time to establish workable incentives to lower greenhouse gases. Let's approach global warming clear-eyed.