Scientific concepts such as net zero are intrinsically scientific. Physics suggests that there is a finite budget of carbon dioxide, along with other greenhouse gases, that is permitted into the atmosphere if the objective is to keep global average temperatures from rising beyond certain limits. Any further releases beyond this budget must be offset by sink removals.
Choosing what is acceptable is a societal decision, but one that is based on climate science. In the Paris Agreement, 197 countries agreed to keep global warming below 2°C and take steps to keep it below 1.5 °C. Assuming a 50% probability of meeting the 1.5 °C goal, 400–800 GtCO2 of remaining carbon budget will remain. In order to stay within this carbon budget, CO2 emissions must peak before 2030 and decline to zero by about 2050.
Net zero, however, is much more than just an idea or a goal that has been set in terms of technology. It also serves as a framework for structuring and understanding global efforts to combat climate change, something that is happening more and more.
To attain net zero, operationalization across various social, political, and economic spheres is required. A range of political, economic, legal, and behavioral issues, as well as ethical judgements, social concerns, political interests, justice components, economic considerations, and technical transitions, could prevent the successful implementation of net zero.
Technically, global net zero will be reached once greenhouse gas (GHG) emissions caused by humans have been reduced to the lowest levels conceivable and any "residual emissions" have been balanced by an equivalent amount of anthropogenic removals that will prevent them from being released into the atmosphere. Anthropogenic removals are the deliberate human activities that remove GHGs from the atmosphere, such as by technology means (direct air capture and storage) or through natural means (land restoration and improved forest management). Furthermore, there isn't much time left, therefore drastically lowering emissions is necessary now more than ever. The carbon budgets calculated by scientists apply to the global atmosphere, rather than individual entities. To turn net zero into a useful frame of reference for decision-makers, the global carbon constraint needs to be translated into individual decarbonization pathways for nation states, sub-national entities, companies and other organizations.
It takes discretion to set such entity-level goals and determine how they interact. The leftover carbon budget can be managed in a variety of ways. Although there is a lot of literature on the topic, in reality it is up to individual emitters and self-regulatory voluntary rules to determine the extent, timing, fairness, and relevance of entity-level net-zero aims. The issue of how a wide range of voluntary commitments sum up to national targets and national targets add up to the global carbon budget remains unanswered.
Currently, there are insufficient procedures for governance, accountability, and reporting. Often, long-term goals are not sufficiently supported by immediate activity. Many organizations are vague about the function of carbon offsets in place of reducing their own emissions and have not yet established specific plans to carry out their commitments1. The social and environmental integrity of some of these offsets is under doubt. As a result, some activists claim that these commitments are little more than "greenwashing."
According to economic model estimates, the most cost-effective strategy to achieve a specific temperature target is to front-load climate action and combine it with long-term planning over a number of years. Early intervention aids (or would have assisted) in overcoming the economic systems' inertia and enables learning and scale effects to take place, lowering technological costs. In especially in developing nations, it increases the development potential of clean innovation and lowers the risk of investing in stranded assets.
Governance experts advise combining long-term net-zero commitments, which establish the direction of travel, with short-term interim objectives, which specify emissions pathways over decision-relevant time frames, to stimulate early emission reductions. The two sets of goals complement one another and reduce the likelihood of long-term political pledges being inconsistent with time. They should be embedded in strong and enforced legal frameworks at the corporate and national levels (that is, contracts, legislation or enforceable regulation).
Energy has traditionally been the primary focus of emissions reduction initiatives, and expanding renewable energy continues to be essential to decarbonization. Though significant tipping points have already been reached. The cost of renewable energy has dropped so dramatically that it now seems difficult to stop the switch to zero-carbon electricity.
Net zero is about extending the focus to "harder-to-treat" areas, like heavy industries, buildings, food and agriculture, aviation, and mining, without detracting from the task of finishing it in the most advanced sectors. Zero-carbon alternatives do exist in the majority of these industries, but they are still expensive and have not gained as much traction as current infrastructure and technology.
A similarly broad strategy for involving stakeholders is necessary to address all emissions. There are indications that alliances in favor of net zero are beginning to form. Community organizations, local governments, boardrooms, regulatory organizations, central banks, global financial institutions, and the courts are all becoming more aware of climate change. Increased use of citizen assemblies and juries as a form of participatory democracy has stoked the discussion over climate change in various nations.
In theory, different levels of residual emissions and various types of compensating removals can lead to net zero. In fact, a net-zero carbon balance that combines very low levels of residual emissions and low levels of multi-decadal removals has a strong argument for being implemented.
Cost and geopolitical constraints, as well as biological, geological, technological, and institutional constraints on our ability to take carbon from the atmosphere and store it durably and safely, will likely restrict the amount of carbon dioxide that can be removed from the atmosphere. Additionally, there are worries about the moral hazard hazards associated with an over-reliance on carbon removal technologies, which could allow for business as usual rather than the severe reduction in fossil fuel consumption.
Prioritizing emission reductions does not mean delaying the ramp-up of carbon dioxide removal or limiting them to "reduction only." The majority of projected routes to reach the Paris Agreement call for a large increase in removals. On both pollution removals and reductions, we must move as quickly as is practical.
Concerns about carbon credits from the social and environmental perspectives center on the veracity of their claimed carbon benefit, including the possibility of non-additionality, the lack of adequate monitoring of emissions avoidance, reduction, or removal, and the existence of unintended side effect. Any company employing carbon credits to deliver net zero would have to exclusively buy carbon "removal" credits since net zero necessitates the physical balance of residual emissions with removals.
One of many urgent socio-ecological challenges—many of them connected—is climate change. As a "threat multiplier," climate change can often exacerbate the harmful effects of other stressors (such changing land use) on ecosystems and the communities that depend on them. In other cases, the basic causes of environmental stresses like climate change are the same. For instance, land-use change is both the second-largest source of greenhouse gas emissions (accounting for 23% of total emissions) and the main cause of biodiversity decreases (accounting for about 30% of declines in the integrity of the world's terrestrial habitats).
Therefore, in theory, nature-based solutions can simultaneously help limit surface warming and slow biodiversity declines while also assisting human societies in countless crucial ways, including public health, livelihoods, and food security. These solutions include protecting or restoring natural ecosystems and sustainably managing working lands and seas.
Therefore, net-zero plans must embrace a whole range of ecosystem services and be integrated into larger strategies for socio-ecological sustainability rather than just pursuing one goal—carbon storage.
The mechanisms through which net-zero prosperity might manifest are beginning to be described in economics literature. This includes, subject to financial restrictions, the contribution that zero-carbon investments can contribute to a short-term, sustainable economic recovery from the COVID-19 epidemic. It also entails the elimination of market and policy flaws that are economically detrimental, such as the predominance of fossil fuel subsidies. Longer term, zero-carbon innovation will start a positive cycle of spending, regeneration, and expansion.
The Task Force Report identified a number of additional actions that can contribute to net zero, such as:
Significantly reducing emissions to the lowest levels practical in line with what is required to achieve the 1.5-degree target, including aggressive decarbonization driven by fundamental changes in the world's energy, urban, industrial, and food systems.
Using only high-quality removal credits to balance residual emissions at net zero and beyond; the use of emission reduction credits must necessarily decrease.
Offsetting any remaining emissions with GHG emission removals through nature-based solutions such as reforestation and/or engineered solutions such as carbon capture and storage. The term "high quality removals" refers to GHG removals that meet additionality criteria (i.e., they wouldn't have happened otherwise), have an accurate baseline, a reliable carbon accounting technique, are extremely durable, and pose little danger of leakage.
Taking into account short- and medium-term goals (together with 2030 or 2050 goals) to assist identify and prioritize certain sectoral and technical revolutions and to encourage quick action and investments.
Addressing Scope 3 emissions, or emissions from the value chain, which are essential for businesses to fulfill credible net zero promises.
Supporting low-carbon transitions and socially just net zero policies across all regions, whether they are carried out by nations or by businesses.
References:
Fankhauser, S., Smith, S.M., Allen, M. et al. The meaning of net zero and how to get it right. Nat. Clim. Chang. 12, 15–21 (2022). https://doi.org/10.1038/s41558-021-01245-w
What You Need to Know About Net Zero. The World Bank. May 23, 2022. https://www.worldbank.org/en/news/feature/2022/05/23/what-you-need-to-know-about-net-zero
The Net-Zero Transition Report. McKinsey & Company. January, 2022. https://www.mckinsey.com/~/media/mckinsey/business%20functions/sustainability/our%20insights/the%20net%20zero%20transition%20what%20it%20would%20cost%20what%20it%20could%20bring/the-net-zero-transition-what-it-would-cost-and-what-it-could-bring-final.pdf
GIORGIEVA, Kristalina. Getting Back on Track to Net Zero: Three Critical Priorities For COP27. IMF Blog. November 4, 2022. https://www.imf.org/en/Blogs/Articles/2022/11/04/getting-back-on-track-to-net-zero-three-critical-priorities-for-cop27
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