Evaluation of the impact of climate change on rainfall for potential landslide triggering in Japan

Abstract

Intense rainfall events associated with climate change may increase future landslide hazards. Therefore, future landslide probability should be constrained using rainfall projections from global climate models (GCMs). However, because landslides can occur in association with various rainfall patterns, such as short-duration (few hours) intense rainfall to long-term accumulated rainfall over a few days, general projections of daily rainfall are inadequate for evaluation of rainfall with landslide-triggering potential. To address this problem, this study adopted a new approach using 72-h GCM rainfall projections based on 100-year rainfall return levels and applied it to 10 regions in Japan where landslides widely occur. We found that rainfall with landslide-triggering potential becomes more frequent toward 2,100 in response to intensified global warming. In some regions, under the scenario that future greenhouse gas emissions continue to increase owing to inadequate regulation, intense rainfall with landslide-triggering potential is projected to become more frequent and widespread, especially after approximately 2060. In relation to this projected spread of the areas of persistent rain, rainfall with landslide-triggering potential might occur synchronously in two to five regions. However, even under the scenario that aerosol emissions are reduced rapidly to mitigate global warming, rainfall might intensify before 2060 in some regions, resulting in a projection of high landslide probability. The presented projections are not definitive and require further refinement; however, they do suggest that the impact of climate change on the frequency and region of hazard of landslide occurrence might change in the future depending on the effort made to mitigate global warming.