Climate change became a toxic political issue after a cap-and-trade bill collapsed in Congress in 2010, and it saw little discussion on the campaign trail.

For the first time since the topic surfaced in a presidential race in 1988, nominees made no mention of climate change during the prime-time television debates this year between the presidential contenders themselves or their running mates. Debate moderators also chose not to ask Obama or Romney about the issue, despite a clamor by climate activists and some not-so-gentle prodding on the part of pundits and scientists.

The silence on the issue became so deafening this election year that some activists dubbed it "climate silence." And until late in the campaign, some environmentalists struggled to summon enthusiasm for the Democratic president's re-election campaign until Obama's assertion that "climate change is not a hoax" brought delegates to their feet at the Democratic National Convention.

But the Obama administration has moved more quietly on some fronts to reduce carbon emissions, including boosting fuel-efficiency standards for automobiles and adopting tighter controls on mercury emissions from power plants. Bloomberg cited both in his op-ed.

Scientists aren't certain whether climate change, including record low levels of sea ice in the Arctic this summer, influenced Hurricane Sandy's path and intensity. They do know, however, that rising sea levels caused primarily by global warming worsened the storm surge and will continue to do so in future such weather events.

Environmentally minded political strategists have been trying to urge the Obama campaign that talking about climate change can be a winning issue on the campaign trail. Betsy Taylor, a political strategist who works with environmentalists, teaches candidates and advocates to talk about putting American ingenuity to use to address global warming, rather than focusing on science. She also urges them to focus on the impacts of extreme weather. In that context, people see climate change as their problem, not a faraway global one.