“Previous failures to reach consensus in climate summits have been attributed, among other factors, to conflicting policies between rich and poor countries, which tend to disagree on the implementation of mitigation measures,” Francisco Santos of the University of Lisbon told environmentalresearchweb. “Our results indicate that the prospects are not that grim, as long as risk perception is high; climate negotiations are partitioned in smaller groups agreeing on local, short-term targets; uncertainty on those targets is limited; and individuals are not biased to be influenced solely by their own wealth class.”

Santos and colleagues found that without homophily – the human tendency to imitate decisions by others who are similar – in their model, wealth inequality may actually increase global co-operation. “Under this circumstance we observe a ‘co-operative’ feedback between the populations of rich and poor, where the poor pave the way for the rich to contribute more, which in turn feeds back into the poor also increasing their tendency to co-operate,” said Santos.

But homophily can easily interrupt such a feedback loop, Santos says, undercutting contributions from poor players when they imitate each other’s decisions. As rich players tend only to compensate for the lower contribution of the poor up to a certain limit, this can lead to negotiations breaking down and all players losing out.

It’s not all bad news though, as it turns out that stubbornness could be helpful. “Such a negative impact of homophily on global co-operation can be overturned if a few unconditional poor co-operators are present in the population,” said Santos. “The impact of ‘obstinate behaviours’ – individuals that, for one reason or another, cannot be moved to change their behaviour – is found to be stronger among the poor than among the rich.”

That said, the presence of obstinate defectors, who won’t co-operate whatever the circumstances, is detrimental, particularly among rich players.

“In reality, given that risk perception is low, targets uncertainty is manifest, and local, bottom-up approaches have yet to spread globally, it is perhaps not surprising that today’s prospects remain gloomy,” said Santos. “It is therefore urgent that individuals become aware of the true risk that we face such that one may finally engage in the development of local initiatives that may foster global co-operation.”

The team’s model is a public good game, where the public good is the welfare of the planet, Santos explained. Everyone benefits from this, whether they contribute to it or not. “Yet, contrary to traditional public goods problems, investments aim at reducing the chances of future losses instead of increasing future returns,” he said. “By understanding such complex adaptive systems, we enhance our ability to find routes to win the ‘game that concerns all of us, and we cannot afford to lose’.”

To represent rich and poor countries, the team created two types of player – the rich, who made up 20% of the population, and the poor, who received lower sums of money to play with at the start of the game. This represented the fact that one-fifth of the world’s countries produce around the same GDP as the remaining four-fifths.

“Each individual – rich and poor – may invest a fraction of this initial endowment to protect the environment, such that a catastrophic climate disaster may be avoided if a minimum number of contributions are made,” said Santos. “Failure to reach this minimum implies that co-operators invest in vain and all endowments are at risk of being lost. In this case, all members will lose their remaining endowments with a given probability, simulating the actual risk of collective disaster due to a climate-related event.”

Now the team is working to add layers of realism to the model, such as higher levels of information, intricate political networks, complex reactive behaviours and different forms of coalition dynamics. “It is comforting that the present results settle the conditions under which successful negotiations may arise in the absence of all these refinements,” said Santos. “The simplicity of our model may be seen as its weakness but also its strength, as it becomes applicable to other collective action problems beyond decision-making towards environmental issues.”

The team reported the results in PNAS.

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