In Bali, developed and developing countries took their first (very) small steps towards addressing climate change together.The key lesson to be drawn from the recently concluded U.N. climate conference in Bali is that the central issue for climate change is no longer the science. It is how rich and poor countries will divide the burden of solving the problem.

The Kyoto Protocol, concluded ten years ago, required significant emissions reductions from the developed world, but imposed no requirements on developing countries. The United States refused to ratify the agreement partly on the grounds that any agreement that exempted poor nations would do little to reduce the overall risks. In the last decade, emissions have been growing at explosive rates in India, Indonesia, Pakistan, Saudi Arabia, and South Korea. At the same time, many developing nations--above all China, whose emissions will soon dwarf, and likely already exceed, those of the United States--have taken a strong stand against emissions limitations, pointing to their relative poverty and their “right to development.”

In Bali, the United States argued that if developed nations were to commit to emissions reductions, developing nations should do so as well. The United States also opposed the idea that wealthy nations should be required to provide significant financial subsidies to poor ones. For its part, the developing world resisted binding emissions limits and insisted that wealthy nations should agree to provide economic support for any mitigation measures.

The final agreement is a compromise, and a remarkably vague one at that. It includes two key provisions. The first, applicable only to the developed world, calls for verifiable “commitments” to reduce greenhouse gas emissions. The second, applicable only to developing countries, does not call for specific “commitments,” but only for “appropriate mitigation actions” that are financed or otherwise supported by the developed countries.

For those who seek a sensible climate change agreement, there is some good news here. For the first time, poor nations, most importantly China, appear to have accepted the idea that they should take measurable steps toward mitigation. Equally important, rich nations have agreed in principle to provide financial help to poor countries, which have consistently resisted reducing emissions on their own. (Climate change is simply not among their top priorities.)

The bad news is that no nation has agreed to do anything but talk. Developed and developing nations have not agreed to binding emissions restrictions. And even if the wealthy nations do adopt “quantified emissions limitations,” everything depends on the size of those limitations. The Bali agreement says nothing about that. And because climate change will hurt some nations much more than others, a final agreement on a common set of abatement measures is likely to be elusive.

The poor nations have not even agreed to consider making binding commitments to restrict their emissions. Other provisions of the agreement suggest that they won’t do much to change their practices unless wealthy nations help foot the bill.

Because the Bali agreement leaves all of the key questions unresolved, it is tempting, and not unreasonable, to dismiss it as a lot of hot air, and as a clear sign that the division between rich and poor nations is now an insuperable obstacle to an effective agreement. In an unusual move, the White House has already expressed reservations about the agreement, particularly about the weakness of the language describing the obligations of poor nations. The United States might properly wonder how a climate treaty could be effective if China, the world's biggest greenhouse gas emitter, has no obligation to scale back its emissions. And if China is expected to take mitigation efforts only if the rich countries pay, a natural question follows: How much are we going to have to pay? If China's statements are taken at face value, and it really believes that it has a right to elevate all of its citizens to first-world levels of prosperity, then the price tag will be astronomical.

But even with these caveats, there is hope. The agreement establishes two starting points for future negotiations. The first, long pressed by the United States, is that if wealthy nations are to agree to significant emissions reductions, their efforts should be accompanied by significant reductions from the developing world. The second, pressed by the poorer nations, is that as a price for undertaking such reductions, the developing world should get significant financial assistance. Finally, rich and poor countries alike seem at least to acknowledge the collective danger that climate change poses. When the next climate meeting takes place, the distance between developed and developing countries won’t seem quite as daunting as it did before Bali. It’s a small victory, to be sure, but in an area of public policy that has counted too few victories over the last decade, it’s one we’ll take.

Eric A. Posner and Cass R. Sunstein teach at the University of Chicago Law School.

By Eric A. Posner and Cass R. Sunstein