A new way for nations to divvy up greenhouse-gas cuts?

If you want to see how hard it will be to get the next round of cuts in greenhouse gases in any new global climate agreement, look at what happened today in Italy.

The good news: The G-8 countries declared that they "recognise the broad scientific view that the increase in global average temperature above pre-industrial levels ought not to exceed 2°C." The communique is available in pdf form on the G-8 meeting's website.

The statement is not exactly a hard and fast commitment to shoot for 2 degrees, but at least it acknowledges that the science points to that level as a kind of climatological line in the sand.

But climate talks between developed and developing countries, aimed at feeding into the broader UN negotiating process, fizzled out. Developing countries were unconvinced that their richer counterparts were willing to commit to rigorous mid-term emissions goals in exchange for developing countries backing a global reduction in emissions of 50 percent below 1990 levels by 2050 -- a goal that would require significant participation by developing countries.

Now along comes a team of researchers from the US, the Netherlands, and Italy that offers what it sees as a more equitable approach to divvying up emissions-reduction duties, at least for now.

It's based on a couple of premises: In the end, people as consumers of resources are ultimately responsible for carbon emissions, whether any one person's contribution is high or virtually nil; and all countries have a least some people whose wealth allows them to consume enough to be counted among "high emitters."

So, the argument goes, set a universal per-person emissions cap. (For a look at how they go about this, you can download a pdf of their research paper, which appears in the current issue of the Proceedings of the National Academy of Sciences.)

Instead of haggling over which nations do what, the approach sets each country's national target by estimating how broad a swath of its population collectively exceeds the allowable per-capita emissions cap and by how much. Their "emissions" are derived from a country's population and income distribution figures and carbon-intensity estimates. For every ton of carbon the high emitters exceed the cap, that ton becomes part of the country's emission-reduction target.

Nearly everyone pitches in

Rich countries collectively still shoulder most of the load under this approach initially. But many developing countries still have to do something, because they have high emitters, however few they may be. And successive national targets for developing countries would become more ambitious as global targets tighten over time and the number of high emitters rises with a country's standard of living.

This approach doesn't aim emission-reduction policies directly at high emitters one by one or even as a group. Instead, a country would use whatever internationally agreed-upon, verifiable mix of tools -- say, cap and trade or approaches such as avoided deforestation -- to meet its national emissions-reduction target.

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