What more can a scientist trying to save us do?

You're on a train and you receive information that leads you to believe that a flood has weakened the scaffolding of a rail bridge ahead. If the train doesn't stop, it may plunge into a ravine. What do you do? The train won't reach the bridge for awhile, so you don't panic yet. You find the conductor and calmly share your information with him, but he shrugs and says his job is to keep the train on schedule. So you walk through the aisles sharing your information with the passengers to see if they can pressure the conductor. Most don't even glance up from their smart phones and magazines. You get desperate, because time is running out. You start yelling that if the train doesn't stop, everyone is doomed, but even those who seemed sympathetic before scowl at you like you're nuts.

Meanwhile, the train keeps barreling toward the bridge.

James Hansen, director of the NASA Goddard Institute for Space Studies and one of the world's foremost atmospheric scientists, is the man on the train. Hansen, who just gave a terrific update on global warming research at my school, which we recorded and posted, is at heart a shy Midwesterner; he is much more comfortable doing research than being in the spotlight.

In the 1980s, however, he became so worried about global warming that he started speaking out. At a 1988 Senate hearing on climate change, he made headlines when he asserted with 99 percent certainty that greenhouse gases from human activities were causing global warming. Since then the correlated surge in atmospheric carbon dioxide and global temperatures has borne out his assertion.

Hansen has continued to do research on climate change and to speak out, even when his candor threatened his career. Officials of the Bush administration repeatedly warned Hansen to curb his tongue—a NASA lawyer even threatened the scientist with prosecution—but he refused to be censored. His growing desperation is evident in his recent book, Storms of My Grandchildren: The Truth about the Coming Climate Catastrophe and Our Last Chance to Save Humanity (Bloomsbury USA, 2009). The book lays out the evidence for human-induced global warming, addresses the doubts of skeptics, and spells out what we should do to avert the worst consequences.

Like its author, Storms is earnest and wonky, especially when discussing the details of global warming research and proposed solutions—notably cap and trade, which Hansen loathes, and fee and dividend, which he likes. As the book's subtitle indicates, Hansen's rhetoric can be strident, for example when he refered to rail cars bearing coal as "death trains." (Hansen has apologized for that language, which has previously been used to describe the trains that carried Jews to Nazi concentration camps.)

But Hansen's lack of polish and tact lends his book force. He criticizes not only global warming skeptics but also environmentalists who oppose nuclear power, which Hansen views as our best hope for replacing fossil fuels. He whacks not only Bush officials but also Bill Clinton, Al Gore and Barack Obama for not acting more aggressively to curb carbon emissions. "Our planet, with its remarkable array of life, is in imminent danger of crashing," he wrote. "Yet our politicians are not dashing forward. They hesitate; they hang back."

Hansen advocates civil disobedience to block fossil-fuel operations; in 2009 he was arrested along with other protestors allegedly obstructing traffic into a coal-mining operation in West Virginia. Now he is trying another tactic: suing the government. Hansen serves as a scientific advisor for Our Children's Trust, an Oregon-based nonprofit formed "to protect Earth's natural systems for current and future generations." The group has organized a lawsuit that a coalition of environmental groups filed last week against the U.S. and other nations in attempt to force them to take measures to cut fossil-fuel emissions.

The suit includes Hansen's claim that it is not enough to keep atmospheric carbon dioxide levels at their current level of 390 parts per million; to avoid damaging the planet, we must roll levels back to 350 parts per million, which is still 70 parts higher than the pre-industrial level. First filed on May 4 in a U.S. district court in California (pdf), the suit claims that U.S. has failed to fulfill its "fiduciary obligation to control atmospheric contamination that causes catastrophic and irreparable damage to our lands, our businesses, our national security and our health."

For reasons that are probably more emotional than rational, I resist Hansen's alarming assertion that if we don't take immediate steps to slash fossil-fuel consumption, we may be doomed. But I respect and admire Hansen as a scientist and an activist. Read his book, listen to his lecture, and decide for yourself if humanity is in danger of going off the rails.

Photo of Hansen by Columbia University