Perhaps the biggest question facing the international climate community is how to divvy up the burden of reducing emissions. The arguments tend to centre on historical responsibility in the wealthy world versus future growth in developing countries, but a new study offers up a different metric: wealthy individuals everywhere (see Reuters, CNN).

The Kyoto Protocol requires developed countries to take on mandatory targets while giving developing countries a temporary pass, but international negotiators hope to craft a new agreement this year. This time around wealthy nations say they are willing to take on more substantial cuts but only if developing countries agree to slow, and eventually reverse, the rapid growth in emissions.

They have a point: like it or not, tackling climate change is impossible without the help of developing countries that are now, according to a recent analysis by the Netherlands Environmental Assessment Agency, responsible for more than half of the global emissions. On the other hand, poor countries are wary of restricting economic development that could lift billions of people out of poverty.

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In their paper, Princeton University’s Shoibal Chakravarty and colleagues argue it would make more sense, in terms of equity, to target rich people rather than rich countries. This approach acknowledges the fact that there are wealthy people all over the world, and that their activities drive a large part of the pollution.

The end result doesn’t look all that different from what is currently being discussed: wealthy countries wind up with stronger commitments while developing countries receive more time to bring their emissions under control. It should be noted that such a calculation would be used only to determine national obligations; each individual country would decide how to go about achieving its commitments (which might or might not involve targeting the rich).

The study has picked up a fair bit of news coverage, but it’s not clear whether such an idea might help break the stalemate in the United Nations climate negotiations. Part of the problem is that it ignores historic emissions: Many developing countries are focusing their proposals on a broader definition of per-capita emissions, which covers both past and future emissions. This approach necessarily increases the burden on wealthy nations, where a lucky few are responsible for most of the pollution in the air today.

For more on this debate, watch for the 9 July issue of Nature, which will include a special report on how developing countries are positioning themselves in advance of the UN climate summit in Copenhagen this December.