I have to say that all the environmentalists I know -- and I tend to hang out with the climate crowd -- care about stopping global warming because of its impact on humans, even if they aren't so good at articulating that perspective. I'm with them.

The reason that many environmentalists fight to save the Arctic National Wildlife Refuge or the polar bears is not because they are sure that losing those things would cause the universe to become unhinged, but because they realize that humanity isn't smart enough to know which things are linchpins for the entire ecosystem and which are not. What is the straw that breaks the camel's back? The 100th species we wipe out? The 1,000th? For many, the safest and wisest thing to do is to try to avoid the risks entirely.

What the day -- indeed, the whole year -- should be about is not creating misery upon misery for our children and their children and their children, and on and on for generations. Ultimately, stopping climate change is not about preserving the earth or creation but about preserving ourselves. Yes, we can't preserve ourselves if we don't preserve a livable climate, and we can't preserve a livable climate if we don't preserve the earth. But the focus needs to stay on the health and well-being of billions of humans because, ultimately, humans are the ones who will experience the most prolonged suffering. And if enough people come to see it that way, we have a chance of avoiding the worst.

It took so long for Bush to even acknowledge the human role in global warming that whenever he even mentions the topic, some people act like it's big news.

But in an era where a consensus has emerged that forceful action is required to save the planet, Bush's essentially empty words are not very different from silence. And to the extent that their intent is to subvert sincere attempts to find solutions, they're actually worse.

Bush's trick on climate change is to wait until others are about to embrace mandatory limits on greenhouse gases, then make a major speech about goals and process, without any specifics on measures or penalties.

"These are issues worth discussing," said Shawn Lawrence Otto, chief executive officer of Science Debate 2008. "Because of the huge impact that science and technology is having on our lives and our policies, voters have a right to assess the candidates on these topics -- and candidates have an obligation to tell voters what they're thinking."

Science and technology are responsible for half of America's post-World War II economic growth, said Otto, but scientific primacy is shifting rapidly to Asia. "To maintain American economic strength going forward, we need to find a way to deal with that -- and the candidates have been virtually silent," he said.

An even larger issue is climate change, which has been identified by the global scientific community as an imminent and almost certainly catastrophic threat.

"Is there a greater moral imperative than the ongoing viability of the planet?" he asked. "Science is about practical solutions to moral questions."

Thanks to Al Gore and others, global warming has gone mainstream. An issue that floated around the peripheries of policy-making for far too long is now triggering unheard of levels of media attention and a rash of legislative proposals.

Even the Bush administration seems to feel the pressure. Although mixed signals continued well into 2006, it's no longer possible to argue that the president and his administration reject mainstream climate science. They've copped to the conclusion that humans are driving global warming, and so have many of the current Republican presidential candidates. Though not as gung ho as Democrats, even many mainstream Republicans see the need to address global warming, with big state governors Arnold Schwarzenegger of California and Charlie Crist of Florida leading the way on behalf of their party.

Earth Hour won't suffer for a lack of gimmicks. Servers wearing glow-in-the-dark necklaces will sell eco-tinis at bars and restaurants in Phoenix. A local yoga house in Michigan will offer sessions by lamplight, and the Sheraton Hotel in Chicago will have check-in by candlelight. Watching the lights wink off in major metropolitan areas might look impressive, but it's worth asking: What's the point? As Roberts himself notes, the energy saved by turning off your lights for an hour "won't make an enormous difference." So, if it won't cut carbon emissions, why bother then with Earth Hour, or Earth Day or Earth Live, last year's daylong concert for the environment?

Because climate change is essentially a political problem, and the language of politics is symbolism. Just because an act is symbolic doesn't mean it empty.