Nearly 200 countries attended the United Nations Framework Convention on Climate Change (UNFCCC) in Copenhagen, Denmark, in December 2009. The aim of the convention was to set up a replacement for the 1997 Kyoto Protocol.
One of the proposals suggested at the Copenhagen convention was the idea of a climate-change aid fund, with donations from richer countries used to help developing countries to offset the financial burden of dealing with the effects of anthropogenic global warming. US Secretary of State Hillary Clinton announced the US is willing to participate in a climate-change aid fund of up to 100 bn US dollars by 2020 – providing certain other countries also commit. Australia, the UK, Norway, Japan and France agreed to take part while other countries said that they would participate only if a formal agreement was signed.
Deciding whether or not to join such an agreement is a classic social dilemma – a situation where individuals must choose whether to cooperate for the good of the group or to defect for personal gain, bearing in mind the whole group suffers if everyone defects.
To better understand the behaviour and decisions that different countries make, Garrison Greenwood, a game theorist at Portland State University, US, set up a social-dilemma game, using an agent-based model.
He based his model on social-dilemma experiments carried out by Manfred Milinski. In Greenwood's model 20 players participated in a 10-round game. During each round players could contribute 0, 2 or 4 euros, with the target being to raise 400 euros for a climate-change fund by the end of the game. Each player started with 40 euros. Assuming the 400 euro target was reached at the end of 10 rounds, players could keep any money remaining in their account, meaning there was no advantage in investing more than necessary. However, if the group failed to meet the target sum then everyone must give up 90% of the money remaining in the account – an incentive to invest.
Averaging over 100 trials Greenwood found that cooperative strategies arose 16% of the time, but defector strategies dominated, emerging 46% of the time. "This didn't really surprise me I'm afraid," he told environmentalresearchweb. "For most countries contributing to a climate-change fund is something of a luxury, and there is going to be an inclination not to contribute."
However, behaviour changed when Greenwood added a "trigger strategy" to his model. Twenty percent of the players were designated to be defectors, who would not contribute to the fund unless a minimum number of other players cooperated first.
Greenwood found that cooperation levels doubled when 40% of the players led the way and contributed upfront. "In this case pressure starts to bear on any country that decides to defect and so they are more likely to jump on the bandwagon," said Greenwood.
Extrapolating this result to the real world could be useful when it comes to bargaining for future climate-change agreements. "The main thing to make sure is that the trigger isn't set too high," said Greenwood, who reported his work in Europhysics Letters (EPL).