パリ協定の影響分析：経済成長とのバランスに課題（The Paris Agreement is Working, But Not Well Enough to Offset Economic Growth）

2025-10-17 ワシントン大学（UW）

Carbon dioxide emissions (top) and carbon intensity (bottom) for the world, China, the U.S. and Germany. Black shows observed trends, green represents each country meeting its NDC and red is a median projection. Carbon intensity is trending down but emissions in China, and the world, are increasing.Jiang et al./Communications Earth and Environment

＜関連情報＞

• https://www.washington.edu/news/2025/10/17/the-paris-agreement-is-working-but-not-well-enough-to-offset-economic-growth/
• https://www.nature.com/articles/s43247-025-02743-x
• https://www.nature.com/articles/nclimate3352

二酸化炭素排出量を削減しパリ協定を満たすための緩和努力は経済成長によって相殺されている Mitigation efforts to reduce carbon dioxide emissions and meet the Paris Agreement have been offset by economic growth

Jitong Jiang,Skylar Shi & Adrian E. Raftery
Nature Earth Environment  Published:17 October 2025
DOI:https://doi.org/10.1038/s43247-025-02743-x

Abstract

Projecting future climate change is important for implementing the 2015 Paris Agreement, which aims to limit greenhouse gas emissions to a level that would keep the global average temperature increase to 2100 below 2 °C. The Intergovernmental Panel on Climate Change uses emissions scenarios for projecting climate change, but since 2017, an alternative fully statistical Bayesian probabilistic approach has been developed. Both approaches rely on an equation that expresses emissions as the product of population, Gross Domestic Product (GDP) per capita, and carbon intensity, namely carbon emissions per unit of GDP. Here, we use data on these quantities for 2015–2024 to probabilistically assess the changes in climate change prospects associated with post-Paris emissions. These show that carbon intensity declined (i.e., improved) substantially over that period, but that overall carbon emissions rose, due to the rapid rise in world GDP, which more than canceled out the progress made. We found that the projected temperature increase to 2100 declined only slightly, from 2.6° C to 2.4 °C. Meanwhile, the chance of staying below 2 °C remained low, at 17%. However, the chance of the most catastrophic climate change, above 3 °C, has gone down substantially, from 26% to 9%.

2100年までに2℃未満の温暖化はありそうにない Less than 2 °C warming by 2100 unlikely

Adrian E. Raftery,Alec Zimmer,Dargan M. W. Frierson,Richard Startz & Peiran Liu
Nature Climate Change  Published:31 July 2017
DOI:https://doi.org/10.1038/nclimate3352

Abstract

The recently published Intergovernmental Panel on Climate Change (IPCC) projections to 2100 give likely ranges of global temperature increase in four scenarios for population, economic growth and carbon use¹. However, these projections are not based on a fully statistical approach. Here we use a country-specific version of Kaya’s identity to develop a statistically based probabilistic forecast of CO₂ emissions and temperature change to 2100. Using data for 1960–2010, including the UN’s probabilistic population projections for all countries^2,3,4, we develop a joint Bayesian hierarchical model for Gross Domestic Product (GDP) per capita and carbon intensity. We find that the 90% interval for cumulative CO₂ emissions includes the IPCC’s two middle scenarios but not the extreme ones. The likely range of global temperature increase is 2.0–4.9 °C, with median 3.2 °C and a 5% (1%) chance that it will be less than 2 °C (1.5 °C). Population growth is not a major contributing factor. Our model is not a ‘business as usual’ scenario, but rather is based on data which already show the effect of emission mitigation policies. Achieving the goal of less than 1.5 °C warming will require carbon intensity to decline much faster than in the recent past.