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Species extinction risk is a crucial indicator of the global impact of climate change on biodiversity. In life cycle impact assessment (LCIA), the relationship between the potentially extinct ratio and temperature is used to calculate characterization factors (CFs) that indicate additional biodiversity impact per unit greenhouse gas emissions, using the biodiversity loss indicator termed potentially disappeared fraction (PDF). However, current methods for calculating CFs that focus on terrestrial biodiversity do not show differences among taxa and regions. Here, we estimated taxon-level CFs based on a species-specific extinction risk approach for determining impact of CO2 emission on terrestrial biodiversity. The extinction risk of a species is defined as the reciprocal of the estimated waiting times for extinction caused by climate-derived habitat loss of the species. Based on the approach, CFs for five taxa—birds, reptiles, mammals, amphibians, vascular plants—were estimated as 0.017, 0.017, 0.025, 0.027, and 0.040 (PDF·km2·year·kton−1), respectively. In addition, CFs that use the number of potentially extinct species (species·kton−1) as indicators were also calculated based on the same species-specific extinction risk approach. The proposed method successfully calculates taxon-level CFs and has the potential to show their regional variations, which contributes to the precise impact assessment on climate-derived biodiversity in LCIA.

What will be the aggregated cost of climate change in achieving the Paris Agreement, including mitigation, adaptation, and residual impacts? Several studies estimated the aggregated cost but did not always consider the critical issues. Some do not address non-market values such as biodiversity and human health, and most do not address differentiating discount rates. In this study, we estimate the aggregated cost of climate change using an integrated assessment model linked with detailed-process-based climate impact models and different discount rates for market and non-market values. The analysis reveals that a climate policy with minimal aggregated cost is sensitive to socioeconomic scenarios and the way discount rates are applied. The results elucidate that a lower discount rate to non-market value—that is, a higher estimate of future value—makes the aggregated cost of achieving the Paris Agreement economically reasonable.