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要旨:
The difficulty of avoiding dangerous climate change arises
from a tension between group and self-interest1–3 and is
exacerbated by climate change’s intergenerational nature4.
The present generation bears the costs of cooperation, whereas
future generations accrue the benefits if present cooperation
succeeds, or suffer if present cooperation fails. Although
temporal discounting has long been known to matter in making
individual choices5, the extent of temporal discounting is
poorly understood in a group setting. We represent the effect
of both intra- and intergenerational discounting4,6,7 through
a collective-risk group experiment framed around climate
change. Participants could choose to cooperate or to risk
losing an additional endowment with a high probability. The
rewards of defection were immediate, whereas the rewards
of cooperation were delayed by one day, delayed by seven
weeks (intragenerational discounting), or delayed by several
decades and spread over a much larger number of potential
beneficiaries (intergenerational discounting). We find that
intergenerational discounting leads to a marked decrease in
cooperation; all groups failed to reach the collective target.
Intragenerational discounting was weaker by comparison. Our
results experimentally confirm that international negotiations
to mitigate climate change are unlikely to succeed if individual
countries’ short-term gains can arise only fromdefection.
