As world leaders meet in Poznan, Poland this week and next to discuss efforts to reduce greenhouse gas emissions causing global warming, it's worth remembering that scientists have known climate change could be a problem for a long time.

Irish scientist John Tyndall first speculated that human-induced global warming might be possible back in 1861 and Nobel Prize-winning chemist Svante Arrhennius had confirmed climate change (with laborious pencil and paper calculations rather than the shortcut of computers) by the end of the 19th century. And a little magazine called Scientific American published an article on the phenomenon back in 1959 that holds up today.

Even back then, the rudimentary outlines of the much-maligned "hockey stick" were visible, showing human-induced warming temperatures over time, despite the fact that U.S. geochemist Charles Keeling had only begun his annual measurements of carbon dioxide (CO₂) levels in the atmosphere in Hawaii a year earlier. And the outcome was clear: average global temperatures would rise much the way that a closed car heats up in the sun.

You may recall that President George W. Bush pledged to do something about climate change when campaigning for the presidency back in 2000—but reneged on that promise once in office. But it appears that President-elect Barack Obama will not follow suit, telling a gathering of governors yesterday that "few issues facing America—and the world—are more urgent than combating climate change":

Among the many pressing issues that President-elect Barack Obama will face when he takes office in January is climate change, which he has called an “immediate threat” and warned has made Earth a “planet in peril.” In an effort to prevent and reverse the problem, he supports a so-called cap-and-trade scheme similar to one now in effect in the U.S. Northeast and the European Union.

Under such a plan, the government sets an overall limit on the amount of pollution allowed and polluters, such as power companies, are sold or given permits to pollute. Those who emit less pollution thanks to a new wind farm, for example, can then sell their excess pollution permits to other companies struggling to meet their quotas. That ensures that the industry stays within the overall emission limit, which declines over time.

It's been a long slog to get to this election day. We all know the campaigns spent millions to get their messages across. But Bob Grant at The Scientist wondered about the environmental cost (log-in required)—specifically how much the campaigns of Sens. Barack Obama and John McCain contributed to global warming. Based on total campaign expenditures—including flying, driving, and printing materials—Grant (with help from consultant Standard Carbon) estimates  that the Obama camp emitted nearly 78,000 tons of climate-change inducing carbon dioxide (CO₂) and the McCain campaign roughly 59,000 tons of CO₂.

Standard Carbon suggests planting 18 square miles of new trees to offset that climate change pollution—the growing trees would theoretically soak up an equivalent amount of CO₂—but such carbon offsets don't address the core of the problem: burning fossil fuels.