For more than two decades, members of the United Nations have sought to forge an agreement to reduce global greenhouse gas emissions, but international climate negotiations have had limited success.

Why? To start with, the motivations were suspect. During the original climate treaty negotiations, Kyoto, the primary drivers in Europe and France insisted on a 1990 target date. What was so special about 1990? Germany had reunified with East Germany, so meeting a 1990 target was easy - they just needed to close a bunch of high-pollution World War II-era Soviet factories. France added more nuclear power after that date so they had an easier time as well. Only America, where anti-nuclear activists had gotten nuclear energy driven from popular favor, a movement which would reach its highwater mark in 1994 when President Bill Clinton and Senator John Kerry gutted nuclear science in America, would have trouble - because we added more coal plants since nuclear power was not going to be approved.

And then other nations just insisted they should be exempt - China, India and Mexico. 

Advocates can run all of the simulations they want and claim the problem is solvable but it's a difficult claim for policy makers to make back home - either emissions cuts are done fairly, in which case a whole lot of poor people can never have air conditioning and cars and better lives, or the UN will try to pick and choose winners and losers, like in the Kyoto agreement, and an American president will never even bother to try and ratify it.

The solution may be to stop flying all over the world throwing fancy banquets for politicians and advocates for hundreds of countries and get the top five in a room and work it out - basically, the UN should not be the UN and just give authority to large countries with the most to gain and lose to settle it.

In a new Nature Climate Change paper, philosophers Ron Sandler, Rory Smead and colleagues suggest that side agreements, such as bilateral commitments between the US and China or those made in venues like the G8 and G20 summits may be even more important than previously suspected in getting something done.

Most climate negotiation simulations have used social dilemma games such as the Prisoner's Dilemma, in which the best interests of the individual agent are not the same as those of the whole. But, as Smead said, "All countries in a sense want to solve this problem—what they disagree on is how to go about solving it."

So rather than using a social dilemma game, the research team used a bargaining negotiation model: Multiple players must coordinate on an agreement with the goal of cutting global greenhouse gas emissions by the targeted amount. While each agent would like to keep his own reductions as low as possible, he would prefer to increase his proposal if it means the group would be more likely to reach a consensus. "If push comes to shove, they'd prefer to do more," Smead said.

The game starts with each player making an initial proposal to reduce emissions by a certain amount. Then the players see what their fellow participants proposed to and readjust their own proposals. Repeating this several times will eventually either lead to a break down in negotiations or an agreement that makes everyone happy.

Is that going to make any advances? No, it is a simplistic model that doesn't take into account such things as national politics and enforcement scenarios, but it reveals potential barriers to successful negotiations that might be hidden in more complex models.

The academics believe a few factors were extremely important in maintaining successful negotiations in their results. In particular, agreements were more likely to be reached if the group was comprised of fewer agents rather than many; if the group consisted of a variety of small and large emitters; and if the perceived individual threat of not reaching an agreement was high.

So make decisions for smaller countries.

"The results bare on a number of political questions," Sandler said. "For instance, while we ultimately need an agreement that includes reductions from almost everyone, side agreements among smaller numbers of participants don't undermine—but may actually promote—the U.N. process."

Since smaller groups are more likely to reach consensus, the researchers said, it would be better for a subgroup of countries to come to a consensus on its own and then bring that single proposal to the larger group.

"It would be much better if the rest of the world could figure out a potential agreement and then invite countries such as China and the U.S. to the table," Smead explained. If that smaller group's offer is sufficient—that is, if it promises to reduce emissions by the proportional amount necessary to achieve the global goal—then it should be successful in the larger venue.

This suggests that efforts such as the G8 and G20 climate summits are actually beneficial to the efforts of the United Nations Framework Convention on Climate Change, which is considered the most important climate bargaining forum. Many have worried that these smaller efforts weaken UNFCCC's work, but the new research disputes that concern.