Politically, climate change is off this year's campaign agenda. Jobs, the economy and social issues are front and center.
But scientists are working as hard as ever to figure out how much the Earth is warming and what to do about it. Some now say it's time for a new strategy, one that gets faster results.
Talk to Durwood Zaelke, for example. Zaelke is a grizzled veteran of the climate wars: He was in Kyoto in 1997 when the world's nations drafted a treaty promising to curb warming, and he has watched that promise fizzle while the planet's temperature continues to rise.
Zaelke says the Kyoto treaty focused too much on the main greenhouse gas: carbon dioxide.
"I mean, it's like picking a fight with the biggest bully in the schoolyard," he says with a note of lament. "You know, you get your lunch money stolen, you get your pants pulled down, and you get sent home humiliated. We've made about that much progress with CO2."
Most CO2 comes from big power plants and factories — the engines of economic development. Few governments have been willing to endanger development with limits on CO2.
Zaelke, who runs the Institute for Governance and Sustainable Development in Washington, D.C., says it's time to look for other climate solutions. "You can't expect one treaty system to address every cause of climate change," he says. "It's too complex of a problem."
A growing number of scientists agree. They're focusing less on CO2 and more on other things that warm the planet, especially ozone and black carbon. Black carbon is mostly soot from burning wood, charcoal and dung.
Climate scientist Drew Shindell with NASA's Goddard Institute for Space Studies at Columbia University says ozone and soot live in the air for only a few months or years before they degrade or fall to Earth. If you slow or stop producing them, pretty soon the atmosphere will be fairly soot and ozone-free.
"So these things really have an immediate and quite powerful, in many cases, effect on climate both at global and regional scales," he says.
Carbon dioxide, on the other hand, stays in the atmosphere for much longer. So curbing CO2 from smokestacks won't show benefits for many decades, or even longer.
Shindell says cutting ozone and soot could slow warming by half a degree Celsius by 2050.
"By averting a half a degree of projected warming, that's really a substantial portion of whether the planet really goes over 2 degrees or stays below that," he says.
Two degrees warmer is when most climate scientists say bad things start happening to the planet.
It wouldn't be cheap; it could cost an average of $250 to cut a ton of pollutant. But Shindell says there are economic reasons for cutting ozone and soot that make it doable.
For example, ozone is created when methane gets into the atmosphere. Methane is essentially natural gas; it escapes from coal mines, livestock waste ponds and pipelines. It's valuable and capturing it saves money. Also, ozone damages commercial crops and causes smog. As for soot, it causes respiratory disease and millions of premature deaths.
Says Shindell: "If you factor in the air quality benefits and their large effects on health, then you find the reductions are really giving you benefits." He says those benefits, on a cost-per-ton-of-pollutant removed, outweigh the costs.
Shindell bases his calculations on wide-ranging assumptions about global health and economic gains, as well as what it would all cost. Some are especially hard to nail down — how crops might respond to less ozone, for example, depends on lots of local conditions. The dollar value for costs and benefits vary widely and are likely to be questioned.
But the study confirms others that say ozone and soot should be added to CO2 on the climate hit list.
And Zaelke says that unlike carbon dioxide, the tools to reduce them are familiar. "We have laws and we have institutions in most countries that already know something about controlling this," he says. "We already know the technology. We already know how to do it."
And it wouldn't take an international treaty to do it, either.
Shindell's research appears in the journal Science