気候変動緩和費用から見たリスク対応戦略

摘要

IPCC WG1AR5では，「人間活動が20世紀半ば以降に観 測された温暖化の主な要因であった可能性が極めて高い (95〜100%の確率)」とされており'、人為的な温室効果ガ ス排出によつて地球温暖化が進行してきていることは極 めて確からしいと考えられる.%The issue of climate change is beset with uncertainty. We focused on climate change mitigation costs, and the impacts of various constraints in the real world on the costs were quantitatively analyzed by using DNE21+ model which is a global energy systems model.(1)The global emission reduction cost per GDP considering NDCs (Nationally Determined Contributions) under the Paris Agreement were estimated as 0.38%. This cost is 6.5 times greater than that under global least-cost strategy. (2) For Japan and U.S., several case studies considering governmental and social constraints on energy mix were carried out. The case studies reveal (i) Japan's NDC could be considerably more costly than the least-cost measures, (ii) NDC of U.S. will be very severe, unless effective bills for emission reductions in addition to CPP (Clean Power Plan) are enacted. In this way, there are many cost-increasing factors in the real world, and their impact seems to be large. Furthermore, there are concerns about increased risk of the climate change issues related to economic downturn due to large climate change mitigation costs. It is important to promote internationally concordant emission reduction efforts and aim at technology innovation for drastic climate mitigation cost reductions.