2021 年 42 巻 5 号 p. 285-294
This paper presents a cost-benefit analysis of climate change with a focus on two tipping elements: melting of Greenland ice sheet (GIS) and collapse of Atlantic meridional overturning circulation (AMOC). We employ an integrated assessment model based on the DICE-2016R2 framework. Effects of melting GIS on AMOC are newly modeled. Simulation results show that the effects of GIS on AMOC largely increase the social cost of carbon and lower the optimal CO2 emissions compared to the original DICE-2016R2. In a case with the GIS effects, the optimal global CO2 emissions reaches zero by around the year 2090, much earlier than the original model, implying the role of low-carbon and negative emissions technologies to manage the impacts and risks of tipping elements. Estimated global average temperature rise in 2100 from the pre-industrial level is also lowered from 3.5 degrees Celsius in the original DICE-2016R2 to 3.2 degrees Celsius with the GIS effects. Our results support that tipping elements and these interactions would be important factors for designing long-term climate strategies.
