Resource Library

“Limiting global mean temperature increase at any level requires global CO2 emissions to become net zero at some point in the future. At the same time, limiting the residual warming of short-lived non-CO2 emissions can be achieved by reducing their annual emissions as much as possible.

“To stabilize global temperature at any level, ‘net’ CO2 emissions would need to be reduced to zero. This means the amount of CO2 entering the atmosphere must equal the amount that is removed. Achieving a balance between CO2 ‘sources’ and ‘sinks’ is often referred to as ‘net zero’ emissions or ‘carbon neutrality’. The implication of net zero emissions is that the concentration of CO2 in the atmosphere would slowly decline over time until a new equilibrium is reached, as CO2 emissions from human activity are redistributed and taken up by the oceans and the land biosphere. This would lead to a near-constant global temperature over many centuries.

“Limiting warming to 1.5°C implies reaching net zero CO2 emissions globally around 2050 and concurrent deep reductions in emissions of non-CO2 forcers, particularly methane (high confidence).”

Citation: Rogelj, J., Shindell, D., Jiang, K., Fifita, S., Forster, P., Ginzburg, V., … & Zickfeld, K. (2018). Mitigation pathways compatible with 1.5 C in the context of sustainable development. In Global warming of 1.5 C (pp. 93-174). Intergovernmental Panel on Climate Change. https://www.ipcc.ch/sr15/

“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. 

“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.”

Citation: , M. R., Friedlingstein, P., Girardin, C. A., Jenkins, S., Malhi, Y., Mitchell-Larson, E., … & Rajamani, L. (2022). Net zero: science, origins, and implications. Annual Review of Environment and Resources, 47, 849-887. https://www.annualreviews.org/doi/abs/10.1146/annurev-environ-112320-105050

“We identify seven attributes of net zero, which are important to make it a successful framework for climate action. The seven attributes highlight the urgency of emission reductions, which need to be front-loaded, and of coverage of all emission sources, including currently difficult ones. The attributes emphasize the need for social and environmental integrity.

“Governance, accountability and reporting mechanisms are currently inadequate. Long-term ambition is often not backed up by sufficient near-term action. Many entities have not yet set out detailed plans to achieve their pledges and are opaque about the role of carbon offsets in place of cutting their own emissions. The environmental and social integrity of some of these offsets is questionable. As a result, some advocates have accused these pledges of amounting to little more than ‘greenwashing’. These concerns do not negate the scientific logic of global net zero. However, they demonstrate the need for clear guardrails to ensure the robustness of net zero as a framework for climate action.

“Prioritizing emission reductions neither equates to ‘reduction only’, nor does it mean delaying the ramp-up of carbon dioxide removal. Most modelled pathways to meet the Paris Agreement involve a significant scaling up of removals. Given that many important technologies are still in their infancy, much investment is and will be needed to ensure that there are enough removal options for residual emissions. We need to make progress as fast as realistically possible on both emission reductions and removals.”

Citation: Fankhauser, S., Smith, S. M., Allen, M., Axelsson, K., Hale, T., Hepburn, C., … & Wetzer, T. (2022). The meaning of net zero and how to get it right. Nature Climate Change, 12(1), 15-21. https://www.nature.com/articles/s41558-021-01245-w#citeas

“We find that early action to reduce both emissions of carbon dioxide and methane simultaneously leads to the best climate outcomes over all timescales. We therefore recommend that companies and countries supplement net zero targets with a two-basket set of interim milestones to ensure that early action is taken for both carbon dioxide and methane. A one-basket approach, such as the standard format for Nationally Determined Contributions, is not sufficient because it can lead to a delay in methane mitigation.

“Studies have also identified multiple shortcomings of current net zero targets, and called for strategies for improvement. Some of those issues are a need for transparency relating to types of GHGs covered and metrics used; consistency in the accounting method for land-use emissions; clarity in definitions and terminology; distinction among carbon dioxide removals, reductions and avoidance; consideration of fairness regarding different timelines for achieving net zero among countries with a diversity of economic conditions; and concern over companies/countries using the long timeline of net zero targets to delay decarbonization

“Proposals to improve net zero targets include but are not limited to transparency in the scope of emissions regarding gas species, sources, and metrics; disclosure of contributions from emissions reductions, removals, and offsets; disclosure of fairness and adequacy of target timeline as required in the Paris Agreement Nationally Determined Contributions (NDCs); long-term roadmap of maintaining net zero or net negative emissions; and plans to monitor and manage carbon storage.”

Citation: Sun, T., Ocko, I. B., Sturcken, E., & Hamburg, S. P. (2021). Path to net zero is critical to climate outcome. Scientific reports, 11(1), 22173. https://www.nature.com/articles/s41598-021-01639-y

“Net zero emissions targets are a useful focal point for policy, linking a global temperature target and socio-economic pathways to a necessary long-term limit on cumulative CO2 emissions.

“Net zero emission targets (including full decarbonization) are useful focal points (Jaeger and Jaeger 2010) for policy, providing a link between technologically feasible socio-economic pathways and a long-term limit on cumulative CO2 emissions. From a climate point of view, capped cumulative CO2 emissions remain the highest priority for temperature stabilization. Emissions in every year contribute to this CO2 budget, and delaying mitigation over the coming decades increases the pressure to achieve net zero CO2 emissions earlier in this century. Once global net zero CO2 emissions are achieved, also the cumulative CO2 budget will be effectively capped.”

Citation: Rogelj, J., Schaeffer, M., Meinshausen, M., Knutti, R., Alcamo, J., Riahi, K., & Hare, W. (2015). Zero emission targets as long-term global goals for climate protection. Environmental Research Letters, 10(10), 105007. https://iopscience.iop.org/article/10.1088/1748-9326/10/10/105007/pdf

“In this paper, we assess the CO2 emissions requirements for global temperature stabilization within the next several centuries, using an Earth system model of intermediate complexity. We show first that a single pulse of carbon released into the atmosphere increases globally averaged surface temperature by an amount that remains approximately constant for several centuries, even in the absence of additional emissions. We then show that to hold climate constant at a given global temperature requires near-zero future carbon emissions. Our results suggest that future anthropogenic emissions would need to be eliminated in order to stabilize global-mean temperatures.

“We emphasize that a stable global climate is not synonymous with stable radiative forcing, but rather requires decreasing greenhouse gas levels in the atmosphere. We have shown here that stable global temperatures within the next several centuries can be achieved if CO2 emissions are reduced to nearly zero. This means that avoiding future human-induced climate warming may require policies that seek not only to decrease CO2 emissions, but to eliminate them entirely.”

Citation: Matthews, H. D., & Caldeira, K. (2008). Stabilizing climate requires near‐zero emissions. Geophysical research letters, 35(4). https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2007GL032388

South Pole’s 2022 net zero report took a closer look at over 1,200 private companies across 12 countries and 15 sectors with a sustainability or corporate social responsibility lead to get an indication of how some of the more climate-aware companies in the market are progressing (or not) on their net zero journey today.

The United Nations Secretary-General, António Guterres, on 31 March 2022, established a High-Level Expert Group on the Net-Zero Emissions Commitments of Non-State Entities to develop stronger and clearer standards for net-zero emissions pledges by non-State entities – including businesses, investors, cities, and regions – and speed up their implementation. The ten recommendations, outlined in the report, are a how-to guide for credible, accountable net-zero pledges and detail what non-State actors need to consider through each stage of their progress towards achieving net-zero ambitions and addressing the climate crisis.

Avoided emissions – emissions savings that occur outside a company’s value chain – offer an additional means to accelerate decarbonization through the development of products and services in line with a 1.5°C pathway. The World Business Council for Sustainable Development (WBCSD) and its member companies, in collaboration with Carbone4 and its Net Zero Initiative and released the “Guidance on Avoided Emissions: Helping business drive innovations and scale solutions toward Net Zero”. Leading global companies, academia and technical experts came together to develop a shared vision of how “Avoided Emissions” could be calculated and leveraged not only by companies but also by financial institutions and governments in their ambition to support and drive climate-aligned decision-making, innovation and purpose definition.