Peter Spotts of the Christian Science Monitor has a helpful overview of the ongoing talks over an international climate treaty to succeed the Kyoto Protocol, which will culminate in the Copenhagen negotiations this December. First, a quick recap of what the main goals are, as envisioned by Yvo de Boer, the executive secretary of the UN Framework Convention on Climate Change:

How would he define success at December’s meeting? First, an agreement must be clear about how much industrial countries aim to reduce greenhouse-gas emissions by 2020, Mr. de Boer said.

Then, it must be clear on what major developing countries—China, India, Mexico, Brazil, and South Africa—will do to limit the growth of their emissions. It must be clear about providing stable and predictable sources of money for adaptation measures in the developing world and for aid in buying the green technologies that will help those countries meet their emissions goals. And it must be clear on how the financial institutions that provide that money will be governed.

One of the big sticking points right now is how much developed countries will actually reduce their emissions. In talks at Bali last year, the industrial countries—save for the United States—proposed to cut greenhouse-gas emissions 25 to 40 percent below 1990 levels by 2020. So how's that shaping up now?

The energy legislation that cleared the US House Energy and Commerce Committee last month would reduce emissions anywhere from1 percent below 1990 levels to 23 percent below, depending on how aggressively some of its provisions are used, according to calculations by the World Resources Institute in Washington.

By contrast, Europe aims to reduce emissions to 20 percent below 1990 levels by 2020 and would sweeten the pot by dropping emissions to 30 percent of 1990 levels if other industrial nations took on aggressive 2020 targets.

Japan is currently weighing its 2020 targets, with proposals ranging from 4 percent above 1990 levels to 25 percent below 1990, Mr. Meyer says. And Australia is reportedly shooting for 25 percent if several conditions are met.

Developed countries are hovering around the recommended targets, but there's a lot of uncertainty still. Ultimately, the wealthy industrial countries are unlikely to clamp down further unless they approve of whatever action developing countries agree to take. And that's a real question mark.

There's zero chance that fast-growing countries like China or India will agree to mandatory reductions in the next decade. They argue that, as a matter of fairness, wealthy countries should cut first, giving poorer countries time to catch up. But developing countries can agree to promote clean-energy projects, ratchet up efficiency standards, and pursue technologies like carbon-capture for coal plants, while reducing their overall carbon intensity in a measurable way. China, for one, is set to surpass its goal of a 20-percent reduction in carbon intensity by 2010 and is reportedly contemplating an 80 percent in carbon-intensity reduction by 2020. This would slow down emissions growth, but not reverse it.

Ideally, these countries would then get on path to implement actual cuts in emissions starting around 2025. According to Climate Progress, Carnegie's Bill Chandler has said that a hard cap could be possible in China by then—a scenario China's Energy Research Institute has been studying seriously. One factor here, as several China experts have told me, is that China is worried about a potential trade war with the EU and United States if it doesn't get serious about reducing emissions. Remember, the Waxman-Markey climate bill gives the White House authority, by 2025, to impose carbon tariffs on countries that aren't complying with global agreements—a touchy subject, but a real part of the dynamic here.

--Bradford Plumer