Climate Warming Mitigation from Nationally Determined Contributions

Abstract

Individual countries are requested to submit nationally determined contributions (NDCs) to alleviate global warming in the Paris Agreement. However, the global climate effects and regional contributions are not explicitly considered in the countries’ decision-making process. In this study, we evaluate the global temperature slowdown of the NDC scenario (ΔT = 0.6°C) and attribute the global temperature slowdown to certain regions of the world with a compact earth system model. Considering reductions in CO₂, CH₄, N₂O, BC, and SO₂, the R5OECD (the Organization for Economic Co-operation and Development in 1990) and R5ASIA (Asian countries) are the top two contributors to global warming mitigation, accounting for 39.3% and 36.8%, respectively. R5LAM (Latin America and the Caribbean) and R5MAF (the Middle East and Africa) followed behind, with contributions of 11.5% and 8.9%, respectively. The remaining 3.5% is attributed to R5REF (the Reforming Economies). Carbon Dioxide emission reduction is the decisive factor of regional contributions, but not the only one. Other greenhouse gases are also important, especially for R5MAF. The contribution of short-lived aerosols is small but significant, notably SO₂ reduction in R5ASIA. We argue that additional species beyond CO₂ need to be considered, including short-lived pollutants, when planning a route to mitigate climate change. It needs to be emphasized that there is still a gap to achieve the Paris Agreement 2-degree target with current NDC efforts, let alone the ambitious 1.5-degree target. All countries need to pursue stricter reduction policies for a more sustainable world.

摘要

:《巴黎协定》规定了各个国家应提交国家自主贡献以缓解全球变暖。然而,各国在制定国家自主贡献时,并未明确考虑全球气候影响和区域减排贡献,因此有必要评估各国的国家自主贡献对减缓气候变化的贡献。本文首先模拟了自出减排情景下相对于无政策情景升温减缓了0.6℃,并通过简化地球系统模型将全球升温减缓归因于全球不同区域的减排行动。在考虑二氧化碳、甲烷、氧化亚氮、黑碳和二氧化硫五种气候强迫物质的减排情况下,经合组织成员国和亚洲国家是减缓全球变暖的两大贡献者,分别贡献了39.3% 和36.8%。拉美国家、中东非国家和转型经济体国家分别贡献了剩下的11.5%、8.9%和3.5%。二氧化碳的减排是区域贡献的决定性因素,但不是唯一因素。其他温室气体也很重要,尤其是对于中东非国家。气溶胶的贡献很小但是显著,特别是亚洲国家中的对二氧化硫的减排。我们认为,在规划减缓气候变化的路线时,需要考虑二氧化碳以外的其他物质,包括短期污染物。需要强调的是,目前的减排政策距离实现《巴黎协定》2℃目标仍有差距,更不必说雄心勃勃的1.5℃目标了。所有国家都需要采取更严格的减排政策,以实现世界的更可持续发展。