Realization of Paris Agreement pledges may limit warming just below 2 °C
Realization of Paris Agreement pledges may limit warming just below 2 °C
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DOI：
10.1038/s41586-022-04553-z
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发表时间：
2022-04-14
期刊：
影响因子：
64.8
通讯作者：
Hackmann, Bernd
中科院分区：
文献类型：
--
作者：
Meinshausen, Malte;Lewis, Jared;Hackmann, Bernd
在《格拉斯哥气候公约》之前的五年里，154个缔约方在其国家自主贡献中提交了新的或更新的2030年减缓目标，76个缔约方提出了更长期的承诺。在2021年联合国气候变化大会（COP 26）之前对承诺的量化表明，将变暖保持在2摄氏度以下的可能性不到50%（2-5）。我们在这里表明，如果所有有条件和无条件的承诺都得到充分和及时的执行，全球变暖可以保持在2摄氏度以下。在根据政府间气候变化专门委员会（气专委）第一工作组对第六次评估报告（6）的贡献对地球系统不确定性的概率特征进行充分实施案例建设时，升温峰值可限制在1.9-2.0摄氏度（5%-95%范围1.4-2.8摄氏度）。我们回顾性地预测了21世纪的变暖，以显示2015年至2021年的总体目标水平如何变化。我们的研究结果依赖于2030年或2050年之后的有时限目标的外推，IPCC 1.5摄氏度特别报告（SR1.5）情景数据库的特征（7）以及承诺的全面实施。对这些因素的更悲观的假设将导致更高的温度预测。第二个独立的排放建模框架预测峰值升温为1.8摄氏度，支持已实现的承诺可以将升温限制在略低于2摄氏度的发现。将变暖限制在“略低于”2摄氏度或1.5摄氏度以下，迫切需要采取政策和行动，在本十年内实现大幅减排，与本世纪中叶全球净零二氧化碳排放保持一致。
Over the last five years prior to the Glasgow Climate Pact(1), 154 Parties have submitted new or updated 2030 mitigation goals in their nationally determined contributions and 76 have put forward longer-term pledges. Quantifications of the pledges before the 2021 United Nations Climate Change Conference (COP26) suggested a less than 50 per cent chance of keeping warming below 2 degrees Celsius(2-5). Here we show that warming can be kept just below 2 degrees Celsius if all conditional and unconditional pledges are implemented in full and on time. Peak warming could be limited to 1.9-2.0 degrees Celsius (5%-95% range 1.4-2.8 degrees C) in the full implementation case-building on a probabilistic characterization of Earth system uncertainties in line with the Working Group I contribution to the Sixth Assessment Report(6) of the Intergovernmental Panel on Climate Change (IPCC). We retrospectively project twenty-first-century warming to show how the aggregate level of ambition changed from 2015 to 2021. Our results rely on the extrapolation of time-limited targets beyond 2030 or 2050, characteristics of the IPCC 1.5 degrees C Special Report (SR1.5) scenario database(7) and the full implementation of pledges. More pessimistic assumptions on these factors would lead to higher temperature projections. A second, independent emissions modelling framework projected peak warming of 1.8 degrees Celsius, supporting the finding that realized pledges could limit warming to just below 2 degrees Celsius. Limiting warming not only to 'just below' but to 'well below' 2 degrees Celsius or 1.5 degrees Celsius urgently requires policies and actions to bring about steep emission reductions this decade, aligned with mid-century global net-zero CO2 emissions.