This review explains the science behind the drive for global net zero emissions and why this is needed to halt the ongoing rise in global temperatures. We document how the concept of net zero carbon dioxide (CO2) emissions emerged from an earlier focus on stabilization of atmospheric greenhouse gas concentrations. Using simple conceptual models of the coupled climate–carbon cycle system, we explain why approximately net zero CO2 emissions and declining net energy imbalance due to other climate drivers are required to halt global warming on multidecadal timescales, introducing important concepts, including the rate of adjustment to constant forcing and the rate of adjustment to zero emissions. The concept of net zero was taken up through the 5th Assessment Report of the Intergovernmental Panel on Climate Change and the United Nations Framework Convention on Climate Change (UNFCCC) Structured Expert Dialogue, culminating in Article 4of the 2015 Paris Agreement. Increasing numbers of net zero targets have since been adopted by countries, cities, corporations, and investors. The degree to which any entity can claim to have achieved net zero while continuing to rely on distinct removals to compensate for ongoing emissions is at the heart of current debates over carbon markets and offsetting both inside and outside the UNFCCC. We argue that what matters here is not the precise makeup of a basket of emissions and removals at any given point in time, but the sustainability of a net zero strategy as a whole and its implications for global temperature over multidecadal timescales. Durable, climate-neutral net zero strategies require like-for-like balancing of anthropogenic greenhouse gas sources and sinks in terms of both origin (biogenic versus geological) and gas lifetime.

中文翻译：

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净零排放：科学、起源和影响

这篇评论解释了推动全球净零排放背后的科学原理，以及为什么需要这样做来阻止全球气温持续上升。我们记录了净零二氧化碳（CO2）排放源于早期对稳定大气温室气体浓度的关注。使用气候-碳循环耦合系统的简单概念模型，我们解释了为什么二氧化碳接近净零2排放和减少其他气候驱动因素导致的净能源失衡需要在数十年的时间尺度上阻止全球变暖，引入重要概念，包括对恒定强迫的调整率和对零排放的调整率。政府间气候变化专门委员会第五次评估报告和联合国气候变化框架公约（UNFCCC）结构化专家对话提出了净零的概念，最终形成了2015年《巴黎协定》第4条。此后，越来越多的国家、城市、企业和投资者采用了净零目标。任何实体可以在多大程度上声称已实现净零排放，同时继续依靠不同的清除量来补偿持续排放，这是当前关于碳市场和《联合国气候变化框架公约》内外抵消的争论的核心。我们认为，这里重要的不是任何特定时间点的一揽子排放和清除的精确构成，而是净零战略作为一个整体的可持续性及其在数十年时间尺度上对全球气温的影响。持久的、气候中性的净零战略需要在来源（生物与地质）和气体寿命方面对人为温室气体源和汇进行同等平衡。