Revved up & shut down.

Dear EarthTalk: How much pollution do motorcycles generate? Are there efforts to make them more eco-friendly?--Matt Lackore, Rochester, MN

Motorcycles typically get about double the gas mileage of even fuel-efficient cars--but that doesn't make them green. Motorcycles are not subject to the same emissions standards as cars and light-duty trucks, though they spew up to 15 times more pollution per mile in the form of hydrocarbons and nitrogen oxides.

More stringent regulations in Europe and the U.S. have forced automakers to adopt cleaner engines, but motorcycle manufacturers have been slow to make advances. According to the European Commission, motorcycles--despite accounting for only three percent of total traffic in Europe--may generate 14 percent of its hydrocarbon emissions by 2010.

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In 2004, California passed legislation to limit emissions from motorcycles to 0.8 grams per kilometer (g/km), down from 1975-era standards of between five and 14 g/km. And in 2005, the United Nations' World Forum for Harmonization of Vehicle Regulations issued a new set of motorcycle emissions guidelines encouraging manufacturers to design greener motorcycles.

The U.S. Environmental Protection Agency (EPA) followed suit, establishing new federal rules that require motorcycle makers to reduce their products emissions by 50 percent. In place since the 2006 model year, these rules should cut hydrocarbon and nitrogen oxide emissions from motorcycles by about 54,000 tons a year, while also saving approximately 12 million gallons of fuel.

Honda, a world leader in greener cars, is developing an "idling stop system" that cuts fuel consumption and emissions by turning off the engine at stop lights and in traffic jams. And Intelligent Energy, a British company, is developing an Emissions Neutral Vehicle (ENV), a motorcycle powered by a detachable hydrogen fuel cell. The vehicle can reach speeds topping 50 miles per hour and can run for up to four hours without refueling. Bigger, faster and longer-running versions of the ENV should become widely available in Europe, the U.S. and elsewhere within a few years.

CONTACTS: California Air Resources Board, [phone], www.arb.ca.gov; Intelligent Energy, [phone], www.intelligent-energy.com.

Dear EarthTalk: How is it that the Bush Administration is said to have "censored" climate scientists?--Anna Edelman, Seattle, WA

Word of the White House censoring federal climate scientists on global warming began leaking out to the press early in George W. Bush's first term in office, but only in the last few years have federal employees been willing to go on record. A report released last January by two leading nonprofits, the Union of Concerned Scientists (UCS) and the Government Accountability Project (GAP), found that nearly half of 279 federal climate scientists who responded to a survey reported being pressured to delete references to "global warming" or "climate change" from scientific reports, while many said they were prevented from talking to the media or had their work edited.

"The new evidence shows that political interference in climate science is ... a system-wide epidemic" says UCS's Francesca Grifo. "Tailoring scientific fact for political purposes has become a problem across many federal science agencies." The issue first arose when Rick Piltz, who worked for a decade coordinating federal research on global warming under Clinton and Bush as part of the U.S. Climate Change Science Program--quit in mid-2005, alleging that his superiors were misusing and abusing the scientific information he provided. Piltz told reporters that Phil Cooney, an official with the President's Council on Environmental Quality (CEQ) who previously worked for an oil industry trade group, had been altering documents published by the program. "The changes created a greater sense of scientific uncertainty about observed climate change and potential climate change," said Piltz. Soon after Piltz's accusations went public, Cooney left CEQ to work for ExxonMobil, which has itself been accused of misrepresenting the science of global warming.

Just when the controversy appeared to be dying down, National Aeronautic and Space Administration (NASA) climate scientist James Hansen told reporters that NASA public affairs staff, under pressure from the Bush Administration, were trying to censor his lectures, papers and website postings. In response, NASA Administrator Michael D. Griffin vowed to support "scientific openness" on climate and other topics.

But Piltz says: "Even if we succeed in lifting this heavy hand of censorship, there is still the problem of getting the political leadership to embrace the findings put forward by the scientists."

CONTACTS: Union of Concerned Scientists, [phone], www.ucsusa.org; U.S. Climate Change Science Program, [phone], www.climatescience.gov.