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Abstract

Maintaining the Earth's climate within habitable boundaries is probably the greatest "public goods game" played by humans. However,with > 6 billion "players" taking part, the game seems to rule out individual altruistic behavior. Thus, climate protection is a problem of sustaining a public resource that everybody is free to overuse, a "tragedy of the commons" problem that emerges in many social dilemmas. We perform a previously undescribed type of public goods experiment with human subjects contributing to a public pool. In contrast to the standard protocol, here the common pool is not divided among the participants; instead, it is promised that the pool will be invested to encourage people to reduce their fossil fuel use. Our extensive experiments demonstrate that players can behave altruistically to maintain the Earth's climate given the right set of circumstances. We find a nonzero basic level of altruistic behavior, which is enhanced if the players are provided with expert information describing the state of knowledge in climate research. Furthermore, personal investments in climate protection increase substantially if players can invest publicly, thus gaining social reputation. This increase occurs because subjects reward other subjects' contributions to sustaining the climate, thus reinforcing their altruism. Therefore, altruism may convert to net personal benefit and to relaxing the dilemma if the gain in reputation is large enough. Our finding that people reward contributions to sustaining the climate of others is a surprising result. There are obvious ways these unexpected findings can be applied on a large scale.