Current level and rate of warming determine emissions budgets under ambitious mitigation
Current level and rate of warming determine emissions budgets under ambitious mitigation
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DOI：
10.1038/s41561-018-0156-y
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发表时间：
2018-08-01
影响因子：
18.3
通讯作者：
Allen, Myles R.
中科院分区：
文献类型：
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作者：
Leach, Nicholas J.;Millar, Richard J.;Allen, Myles R.
最近对二氧化碳(CO2)排放剩余预算的估计与将全球变暖控制在1.5摄氏度以内的估计之间存在一些差异，原因是对迄今为止相对于工业化前条件的变暖水平的估计不同，但不是全部。在这里，我们表明，由于简单的几何原因，如果预算以二氧化碳强迫当量排放量的形式表示，那么人类导致的变暖水平和速度的组合可以非常准确地预测到在广泛的情景中达到峰值变暖的剩余排放预算。反过来，如果(但只有当)非二氧化碳驱动因素对全球变暖的贡献几乎保持不变，就像它在一些雄心勃勃的缓解情景中所做的那样，这些预测反过来又预测了二氧化碳排放预算，这表明，从2017年年中开始，1.5摄氏度的最佳估计剩余预算约为当前排放量的22年，范围为13-32年。这提供了一个简单、透明和独立于模型的衡量在实现雄心勃勃的温度稳定目标方面取得进展的指标，可用于为《巴黎协定》的评估进程提供信息。它不太适用于不那么雄心勃勃的目标。当前变暖的替代定义和非二氧化碳驱动因素的情景给出了较低的1.5摄氏度预算。综合评估研究中广泛使用的MAGICC SIMPLE建模系统的预算较低，反映出其模拟的当前升温速率相对较高。
Some of the differences between recent estimates of the remaining budget of carbon dioxide (CO2) emissions consistent with limiting warming to 1.5 degrees C arise from different estimates of the level of warming to date relative to pre-industrial conditions, but not all. Here we show that, for simple geometrical reasons, the combination of both the level and rate of human-induced warming provides a remarkably accurate prediction of remaining emission budgets to peak warming across a broad range of scenarios, if budgets are expressed in terms of CO2-forcing-equivalent emissions. These in turn predict CO2 emissions budgets if (but only if) the fractional contribution of non-CO2 drivers to warming remains approximately unchanged, as it does in some ambitious mitigation scenarios, indicating a best-estimate remaining budget for 1.5 degrees C of about 22 years' current emissions from mid-2017, with a 'likely' (1 standard error) range of 13-32 years. This provides a simple, transparent and model-independent metric of progress towards an ambitious temperature stabilization goal that could be used to inform the Paris Agreement stocktake process. It is less applicable to less ambitious goals. Alternative definitions of current warming and scenarios for non-CO2 drivers give lower 1.5 degrees C budgets. Lower budgets based on the MAGICC simple modelling system widely used in integrated assessment studies reflect its relatively high simulated current warming rates.