Depending on your point of view, carbon dioxide is a good thing (nourishing to plants), or excess carbon dioxide (helping warm the climate) is coming from everywhere–cars, factories, power plants that burn coal or oil or gas. Today the issue is air travel. The EPA says aircraft account for 12 percent of the greenhouse gas emissions from American transportation, 3 percent of U.S. output overall. (See its summary HERE; you’ll hit pay dirt on p. 3 of 393.) Today the Attorneys General of California, Connecticut, New Jersey and New Mexico, the City of New York, the Pennsylvania Department of Environmental Protection and the District of Columbia have joined with a bunch of environmental groups to call for curbs on the carbon dioxide emissions from airplanes. Jerry Brown, the California Attorney General, in a statement at a Los Angeles news conference: "the EPA should have taken action by now to curb these emissions. Not to do so, ignores the tremendous opportunity for technological innovations that can increase efficiency and reduce emissions…." More HERE. He continues, “Aircraft engines burn massive quantities of fossil fuels and inject greenhouse gas pollution at high altitudes—-right where these emissions have a heightened negative impact.” He and others say that with fairly simple steps, aviation could cut its emissions ten percent. The full petition is HERE, among other places. You’ll recall that back in April the Supreme Court ruled the EPA has authority–and to advocates, an obligation–to regulate carbon dioxide as an "air pollution agent" that affects public health and welfare. The petitioners today have already gone after ocean-going ships. Aircraft are a knottier issue. Airlines, which struggle with the ups and downs of fuel prices, have long tried to cultivate a green image. Some advertise that they tell their pilots to taxi on only one engine; the new Boeing 787 is touted for its fuel efficiency: "The airplane will use 20 percent less fuel for comparable missions than today’s similarly sized airplane." The Air Transport Association, trade group for major airlines, says it’s not afraid of the EPA, but it’s already doing plenty. In response to a bill last month by Sens. Lieberman and Warner, it wrote that airlines are "continually improving our fuel efficiency through reinvestment in technology and more fuel efficient operations. In fact, U.S. commercial airlines (passenger and cargo combined) have improved their fuel efficiency by 103 percent since 1978, which (given the one-to-one relationship between fuel consumption and carbon dioxide (CO2)) has resulted in commensurate CO2 emissions savings." They’ve posted more on their efforts HERE. So. Does every bit help? Or has the water already been wrung from this stone?