WASHINGTON - "Cash for clunkers" could have the same effect on global warming pollution as shutting down the entire country - every automobile, every factory, every power plant - for an hour per year. That could rise to three hours if the program is extended by Congress and remains as popular as it is now.
Climate experts aren't impressed.
Compared to overall carbon dioxide emissions in the United States, the pollution savings from cash for clunkers do not noticeably move the fuel gauge. Environmental experts say the program - conceived primarily to stimulate the economy and jump-start the auto industry - is not an effective way to attack climate change.
"As a carbon dioxide policy, this is a terribly wasteful thing to do," said Henry Jacoby, a professor of management and co-director of the Joint Program on the Science and Policy of Global Change at MIT. "The amount of carbon you are saving per federal expenditure is very, very small."
Officials expect a quarter-million gas guzzlers will be junked under the original $1 billion set aside by Congress - money that is now all but exhausted.
Calculations by The Associated Press, using Department of Transportation figures, show that replacing those fuel hogs will reduce carbon dioxide emissions by just under 700,000 tons a year. While that may sound impressive, it's nothing compared to what the U.S. spewed last year: nearly 6.4 billion tons (and that was down from previous years).
That means on average, every hour, America emits 728,000 tons of carbon dioxide. The total savings per year from cash for clunkers translates to about 57 minutes of America's output of the chief greenhouse gas.
Likewise, America will be using nearly 72 million fewer gallons of gasoline a year because of the program, based on the first quarter-million vehicles replaced.
Vehicle owners who trade in an older, gas-guzzling truck or car for a newer fuel-efficient vehicle can get $3,500 to $4,500 in rebates. On average each year, they will save 287 gallons of gas, more than $700 in fuel costs and close to 3 tons in carbon dioxide pollution.
The House has passed a bill at President Barack Obama's request to pump an additional $2 billion into the program. If the Senate follows suit, the potential effect on pollution and energy would triple. But experts say that it is still not much compared to the overall problem.
On Tuesday, the Senate cleared the way for a vote giving eager car buyers until Labor Day to cash in on rebates up to $4,500 for trading in their gas-guzzlers for new, higher-mileage models.
Senate Majority Leader Harry Reid declared he had the votes to pass a $2 billion "cash for clunkers" measure already approved by the House. It would replenish the all-but-exhausted $1 billion program and provide rebates for up to a half-million more Americans in the next month.
Despite reservations, Reid's GOP counterpart, Mitch McConnell of Kentucky, predicted his party would not block a vote and "the matter will be completed."