The level of climate-change mitigation depends on how humans assess the risk arising from missing the 2°C target

Abstract

The established international 2°C target stipulates that global warming should be limited to below 2°C compared with pre-industrial periods; this has emerged as the most prominent interpretation of how to avoid dangerous climate change. The 2°C target was confirmed and made legally binding in the Paris agreement at the "climate summit" (Conference of Parties 21, COP21) in December 2015. But despite agreement on the target, greenhouse-gas emissions are unlikely to fall soon and fast enough to meet the target, raising the question of whether this target needs to be revised or reinterpreted, and also of why there is insufficient cooperation toward emissions reduction despite the risk of dangerous climate change. Previous theoretical and experimental research has suggested that cooperation towards emissions reduction is undermined by uncertainty about the threshold marking the transition to dangerous climate change. However, even if the threshold and hence the location of the target are known precisely, uncertainty ensues because of an unknown risk that arises from missing the collective target. How humans deal with this risk has not been investigated experimentally. Here we investigate how individuals behave under different risk scenarios if a collective target is missed. We perform economics experiments framed as a collective-risk social dilemma and directly examine the extent to which human subjects trade pay-out reduction for risk. We show that a reduced assessed risk arising from missing the collective target leads to reduced contributions towards the target; but that risk reduction causes the subjects almost to maximize their individual pay-out by balancing the effort to reach the target against the risk posed by missing it. We provide quantitative support for the argument that group contributions toward the collective target can be interpreted as proportional to mitigated warming. We conclude that reinterpretation of the 2°C target as less strict causes additional warming. However, our subjects deal effectively with a risk of dangerous climate change that they assess to depend gradually on global warming. Our results suggest that, if the additional warming is judged to be acceptable, a less strict interpretation of the 2°C target might support finding a trade-off between the effort put into climate mitigation and the risk of dangerous climate change.

Global expansion and redistribution of Aedes-borne virus transmission risk with climate change

“…Total mitigation (down to pre-industrial baselines) would presumably prevent this redistribution of global risk more effectively. Given the current insufficient response to curb carbon emissions and keep temperatures below the 2°C warming target [63], models such as those presented here can be useful as a means to anticipate possible future changes in climate and temperature-driven transmission risk, depending on the degree of mitigation achieved.…”

Dishonesty in health care practice: A behavioral experiment on upcoding in neonatology

“…In sum, we are aware that the experimental approach leaves out most of the real-world complexity and should be regarded as a "proof of principle" (Hagel, Milinski, & Marotzke, 2017). For example, one might argue that upcoding is a product of decisions that often take place outside of the domain of any individual health care provider.…”

“…In German neonatal care units, upcoding of birth weights is at the discretion of individual doctors, midwives, or nurses involved in the delivery of preterm infants in neonatal care units. In sum, we are aware that the experimental approach leaves out most of the real-world complexity and should be regarded as a "proof of principle" (Hagel, Milinski, & Marotzke, 2017). This is the strength but at the same time the limitation of any experimental study (e.g., Falk & Fehr, 2003;Falk & Heckman, 2009).…”

Staring at the Abyss: a neurocognitive grounded agent-based model of collective-risk social dilemma under the threat of environmental disaster

“…The agents do not know the whereabouts of the tipping point. The uncertainty lies in personal knowledge (Tavoni et al 2011;Barrett and Dannenberg 2012;Dannenberg et al 2015;Hagel et al 2016Hagel et al , 2017Kumar and Dutt 2019). We adopt a deterministic threshold-based tipping point, unlike Milinski et al (2008), where the environmental disaster would have happened with a certain probability if the agents had not reached the target.…”