In hot pursuit of polluters

In midwinter, John Magnuson looks out his window across Wisconsin's Lake Mendota, hoping to see a swath of ice several miles long and a foot or more thick. But during several recent winters, all he saw was open water.

That's not how Wisconsin winters used to be - at least not according to 150 years of ice-cover data Dr. Magnuson, a university professor, has compiled on this seven-mile-long lake near Madison.

Lake Mendota was covered with ice four months of the year in the 1850s, compared with just 2.5 months today. Disappearing lake ice is a simple gauge widely considered among the clearest and most reliable scientific evidence that the planet is warming.

But would lake-ice data hold up, or melt, in a court of law?

An answer may come as soon as this fall as legions of scientists, possibly including Magnuson, are summoned to appear as expert witnesses in a groundbreaking case that will test the limits of environmental law and the science undergirding climate-change theory.

In a complaint filed last month in federal district court in New York, eight states (Wisconsin, Vermont, Rhode Island, New York, New Jersey, Iowa, Connecticut, and California) claimed that global warming is damaging crops, tourism, beaches, citizens' health, forests, and fish - and threatening coastal communities as sea levels rise.

Targeted in the suit are the nation's five largest public utilities. By burning coal to generate electricity - and spewing some 650 million tons of carbon-dioxide exhaust a year - the companies are major contributors to global warming, which is damaging states, the suit claims.

Unlike state lawsuits against tobacco companies, the states are not asking for damages. Instead, they want the power companies to cap their CO2 emissions. On the surface, it might seem a fairly easy case.

The standard for convicting the defendants is a "preponderance of the evidence" - a greater than 50 percent certainty that the companies are responsible for the damages. This is a far lower bar than the criminal court's "beyond a reasonable doubt" standard. Indeed, the vast majority of climate scientists now agree the planet is indeed warming and that carbon dioxide is the main villain.

"If it weren't so hard, difficult, and fraught with political controversy, the science of global warming would be a no-brainer," says Jerry Mahlman, a climate scientist with the National Center for Atmospheric Research in Boulder, Colo. "The fundamental physics of human-caused climate warming was well-known 25 years ago."

The challenge lies in the details.

For example, scientists can demonstrate that the increase in carbon dioxide and other greenhouse gases has caused a 1 degree F. rise in global temperatures since 1900. But the suit alleges that in sections of the United States, greenhouse gases have caused a jump of 2 to 4 degrees - and that future increases will cause further damage. That's tough to prove because computer models of climate change are much less conclusive when attempting to predict regional or statewide climate impacts from warming - and the rate of that warming, Mahlman and others acknowledge.

The case will be anything but a slam dunk, says Zygmunt Plater, a law professor at Boston College. "The plaintiffs [the states] have to say there has been substantial harm to the public welfare and health caused by the defendants [the companies] either negligently or knowingly."

Still, hard evidence like Magnuson's lake-ice data does show local effects of warming, say proponents of the suit.

"The facts are there and the law is there," says Thomas Dawson, assistant attorney general for the state of Wisconsin. "The science of global warming is solid."

"The science is more than conclusive enough," adds Matt Pawa, a lawyer working on a companion suit filed on behalf of the Natural Resources Defense Council. "It's well beyond the threshold that is required to establish a preponderance of the evidence. Scientists are well beyond 50 percent certain that CO2 emissions cause global warming."

Mr. Pawa acknowledges that the injuries cited in the states' complaint are not all supported by the same amount of scientific certainty. But the focus undoubtedly will be on proving those injuries where there is a high degree of scientific evidence to back up the claim.

Take, for instance, sea level rise in and around New York City, cited as a current - and future - injury in the suit. Many scientists agree that as the earth has warmed, glaciers and polar ice have melted and warming oceans have expanded. The rising sea level is measurable - up an inch per decade in New York since 1900.

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