![]() ![]() ![]() A series of papers noted the longevity of the impact of fossil carbon emissions 7, 8, 9 and the monotonic, near-linear (so far) relationship between cumulative net anthropogenic CO 2 emissions and CO 2-induced surface warming 10, 11, 12, 13. Net zero is just a number, begging the question ‘net zero what?’ For CO 2, the answer emerged in the late 2000s from understanding what it would take to halt the increase in global average surface temperature due to CO 2 emissions. 4), the management and disclosure of climate risks 5, and the use of carbon offsets 6. The seven attributes complement an emerging set of operational principles and criteria, which have been put forward to govern specific net-zero decisions, such as country-level target setting 3, the design of institution-level net-zero commitments (, and ref. This Perspective recapitulates the scientific logic behind net zero and sets out the attributes we believe are important to turn it into a successful framework for climate action across countries. Getting net zero, the frame of reference, right is therefore essential. There are numerous ethical judgements, social concerns, political interests, fairness dimensions, economic considerations and technology transitions that need to be navigated, and several political, economic, legal and behavioural pitfalls that could derail a successful implementation of net zero. It is also a frame of reference through which global action against climate change can be (and is increasingly) structured and understood.Īchieving net zero requires operationalization in varied social, political and economic spheres. However, net zero is much more than a scientific concept or a technically determined target. Staying within this carbon budget requires CO 2 emissions to peak before 2030 and fall to net zero by around 2050 2. Meeting the 1.5 ☌ goal with 50% probability translates into a remaining carbon budget of 400–800 GtCO 2. ![]() Under the Paris Agreement, 197 countries have agreed to limit global warming to well below 2 ☌ and make efforts to limit it to 1.5 ☌. The acceptable temperature rise is a societal choice, but one informed by climate science. Beyond this budget, any further release must be balanced by removal into sinks. If the objective is to keep the rise in global average temperatures within certain limits, physics implies that there is a finite budget of carbon dioxide that is allowed into the atmosphere, alongside other greenhouse gases. Net zero is intrinsically a scientific concept. Almost two-thirds of global emissions and a slightly higher share of global gross domestic product are already covered by net-zero targets 1. Now climate ambition is increasingly expressed as a specific target date for reaching net-zero emissions, typically linked to the peak temperature goals of the Paris Agreement. Historically, climate ambition has either been formulated as a stabilized level of atmospheric concentrations (for example, in the 1992 United Nations Framework Convention on Climate Change) or as a percentage emissions reduction target (for example, in the 1997 Kyoto Protocol). Climate policy has a new focus: net-zero emissions. ![]()
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