Towards high-quality net-zero targets

Author(s):  
Joeri Rogelj ◽  
Andy Reisinger ◽  
Annette Cowie ◽  
Oliver Geden

<p>With the adoption of the Paris Agreement in 2015 the world has decided that warming should be kept well below 2°C while pursuing a limit of 1.5°C above preindustrial levels. The Paris Agreement also sets a net emissions reduction goal: in the second half of the century, the balance of global anthropogenic greenhouse gas emissions and removals should become net zero. Since 2018, in response to the publication of the IPCC Special Report on Global Warming of 1.5°C, a flurry of net zero target announcements has ensued. Many countries, cities, regions, companies, or other organisations have come forward with targets to reach net zero, or become carbon or climate neutral. These labels describe a wide variety of targets, and rarely detailed. Lack of transparency renders it impossible to understand their ultimate contribution towards the global goal. Here we present a set of key criteria that high-quality net zero targets should address. These nine criteria cover emissions, removals, timing, fairness and a long-term vision. Unless net zero targets provide clarity on these nine criteria, we may not know until it is too late whether the collective promise of net zero targets is adequate to meet the global goal of the Paris Agreement.</p>


2021 ◽  
Author(s):  
Tom M. L. Wigley

Abstract This paper provides an assessment of Article 4.1 of the Paris Agreement on climate; the main goal of which is to provide guidance on how “to achieve the long-term temperature goal set out in Article 2”. Paraphrasing, Article 4.1 says that, to achieve this end, we should decrease greenhouse gas (GHG) emissions so that net anthropogenic GHG emissions fall to zero in the second half of this century. To aggregate net GHG emissions, 100-year Global Warming Potentials (GWP-100) are commonly used to convert non-CO2 emissions to equivalent CO2 emissions. As a test case using methane, temperature projections using GWP-100 scaling are shown to be seriously in error. This throws doubt on the use of GWP-100 scaling to estimate net GHG emissions. An alternative method to determine the net-zero point for GHG emissions based on radiative forcing is derived. This shows that the net-zero point needs to be reached as early as 2036, much sooner than in the Article 4.1 window. Other scientific flaws in Article 4.1 that further undermine its purpose to guide efforts to achieve the Article 2 temperature targets are discussed.



2021 ◽  
Author(s):  
Robert Brecha ◽  
Gaurav Ganti ◽  
Robin Lamboll ◽  
Zebedee Nicholls ◽  
Willion Hare ◽  
...  

Abstract Since its adoption in 2015, governments, international agencies and private entities have increasingly recognized the implications of the Paris Agreement’s 1.5°C long-term temperature goal (LTTG) for greenhouse gas emissions reduction planning in both the near- and long-term. Governments have submitted or are preparing updates of their Nationally Determined Contributions (NDCs) and are encouraged to submit long term low greenhouse gas development plans (Article 4 of the Agreement1), aimed at aligning short- and long-term strategies. The foundations on which country targets are based are guided, directly or indirectly, by a variety of sources of information judged to be authoritative, including scientific research institutes2, international agencies, or private companies. Importantly, such authoritative sources also affect planning and decision making by investors3 who aim to anticipate climate policies, and their decisions in turn can drive or hold back setting ambitious emissions-reduction targets.



2021 ◽  
Vol 258 ◽  
pp. 9-11
Author(s):  
Dawn Holland ◽  
Hande Kucuk ◽  
Miguel León-Ledesma

Climate change is one of the most serious risks facing humanity. Temperature rises can lead to catastrophic climate and natural events that threaten livelihoods. From rising sea levels to flooding, bush fires, extreme temperatures and droughts, the economic and human cost is too large to ignore. More than 190 world leaders got together in Glasgow during November 2021 at the UN’s COP26 climate change summit to discuss progress on the Paris Agreement (COP21) and to agree on new measures to limit global warming. In Paris, countries agreed to limit global warming to well below 2° and aim for 1.5° as well as to adapt to the impacts of a changing climate and raise the necessary funding to deliver on these aims. However, actions to date were not nearly enough as highlighted by the IPCC (2018) special report. The world is still on track to reach warming above 3° by 2100. As evident from figure 1, global temperatures have been on a steadily increasing path since the start of the 20th century and this process has substantially accelerated since the beginning of the 1980s. This has been unevenly distributed, with temperatures in the Northern hemisphere being a full 1°C higher than for the 1961–1990 average, whilst temperatures in the Southern hemisphere have increased by almost 0.5°C.



2021 ◽  
Vol 169 (1-2) ◽  
Author(s):  
Tom M. L. Wigley

AbstractThis paper provides an assessment of Article 4.1 of the Paris Agreement on climate; the main goal of which is to provide guidance on how “to achieve the long-term temperature goal set out in Article 2”. Paraphrasing, Article 4.1 says that, to achieve this end, we should decrease greenhouse gas (GHG) emissions so that net anthropogenic GHG emissions fall to zero in the second half of this century. To aggregate net GHG emissions, 100-year global warming potentials (GWP-100) are commonly used to convert non-CO2 emissions to equivalent CO2 emissions. The GWP-scaling method is tested using methane as an example. The temperature projections using GWP-100 scaling are shown to be seriously in error. This throws doubt on the use of GWP-100 scaling to estimate net GHG emissions. An alternative method to determine the net-zero point for GHG emissions based on radiative forcing is derived, where the net-zero point is identified with the maximum of GHG forcing. This shows that, to meet the Article 2 warming goal, the net-zero point for GHG emissions needs to be reached as early as 2036, much sooner than in the Article 4.1 window. Other scientific problems in Article 4.1 that further undermine its purpose to guide efforts to achieve the Article 2 temperature targets are discussed.



Author(s):  
J. Fuglestvedt ◽  
J. Rogelj ◽  
R. J. Millar ◽  
M. Allen ◽  
O. Boucher ◽  
...  

The main goal of the Paris Agreement as stated in Article 2 is ‘holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C’. Article 4 points to this long-term goal and the need to achieve ‘balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases'. This statement on ‘greenhouse gas balance’ is subject to interpretation, and clarifications are needed to make it operational for national and international climate policies. We study possible interpretations from a scientific perspective and analyse their climatic implications. We clarify how the implications for individual gases depend on the metrics used to relate them. We show that the way in which balance is interpreted, achieved and maintained influences temperature outcomes. Achieving and maintaining net-zero CO 2 -equivalent emissions conventionally calculated using GWP 100 (100-year global warming potential) and including substantial positive contributions from short-lived climate-forcing agents such as methane would result in a sustained decline in global temperature. A modified approach to the use of GWP 100 (that equates constant emissions of short-lived climate forcers with zero sustained emission of CO 2 ) results in global temperatures remaining approximately constant once net-zero CO 2 -equivalent emissions are achieved and maintained. Our paper provides policymakers with an overview of issues and choices that are important to determine which approach is most appropriate in the context of the Paris Agreement. This article is part of the theme issue ‘The Paris Agreement: understanding the physical and social challenges for a warming world of 1.5°C above pre-industrial levels'.



2021 ◽  
Author(s):  
Niklas Höhne ◽  
Matthew Gidden ◽  
Michel Elzen ◽  
Frederic Hans ◽  
Claire Fyson ◽  
...  

Abstract The wave of national net zero CO2 and greenhouse gas emission targets could, if fully implemented, reduce best estimates of projected global average temperature increase to 2.1–2.4°C by 2100 and could bring achievement of the Paris Agreement within reach. 127 countries are discussing, have announced or have adopted net zero targets, which together cover 63% of global emissions. Together, these net zero targets could significantly lower projected global warming compared to currently implemented policies (2.9 to 3.2°C) or to the pledges submitted to the Paris Agreement (2.6 to 2.9°C).



2021 ◽  
Author(s):  
Alaa F. Eftaiha ◽  
Abdussalam K. Qaroush ◽  
Areej K. Hasan ◽  
Khaleel I. Assaf ◽  
Feda'a Al-Qaisi ◽  
...  

CO2 is the most influential greenhouse gas with its drastic effects all over the world. Meanwhile, global warming is considered as a hot topic to different slices of scientists dealing...



2012 ◽  
Vol 9 (3) ◽  
pp. 3693-3738 ◽  
Author(s):  
M. S. Carter ◽  
K. S. Larsen ◽  
B. Emmett ◽  
M. Estiarte ◽  
C. Field ◽  
...  

Abstract. In this study, we compare annual fluxes of methane (CH4), nitrous oxide (N2O) and soil respiratory carbon dioxide (CO2) measured at nine European peatlands (n = 4) and shrublands (n = 5). The sites range from northern Sweden to Spain, covering a span in mean annual air temperature from 0 to 16 °C, and in annual precipitation from 300 to 1300 mm yr−1. The effects of climate change, including temperature increase and prolonged drought, were tested at five shrubland sites. At one peatland site, the long-term (>30 yr) effect of drainage was assessed, while increased nitrogen deposition was investigated at three peatland sites. The shrublands were generally sinks for atmospheric CH4 whereas the peatlands were CH4 sources, with fluxes ranging from −519 to +6890 mg CH4-C m−2 yr−1 across the studied ecosystems. At the peatland sites, annual CH4 emission increased with mean annual air temperature, while a negative relationship was found between net CH4 uptake and the soil carbon stock at the shrubland sites. Annual N2O fluxes were generally small ranging from –14 to 42 mg N2O-N m−2 yr−1. Highest N2O emission occurred at the sites that had highest concentration of nitrate (NO3−) in soil water. Furthermore, experimentally increased NO3− deposition led to increased N2O efflux, whereas prolonged drought and long-term drainage reduced the N2O efflux. Soil CO2 emissions in control plots ranged from 310 to 732 g CO2-C m−2 yr−1. Drought and long-term drainage generally reduced the soil CO2 efflux, except at a~hydric shrubland where drought tended to increase soil respiration. When comparing the fractional importance of each greenhouse gas to the total numerical global warming response, the change in CO2 efflux dominated the response in all treatments (ranging 71–96%), except for NO3− addition where 89% was due to change in CH4 emissions. Thus, in European peatlands and shrublands the feedback to global warming induced by the investigated anthropogenic disturbances will be dominated by variations in soil CO2 fluxes.



2020 ◽  
Author(s):  
Joeri Rogelj ◽  
Daniel Huppmann ◽  
Volker Krey ◽  
Keywan Riahi ◽  
Leon Clarke ◽  
...  

<p>To understand how global warming can be kept well-below 2°C and even 1.5°C, climate policy uses scenarios that describe how society could transform in order to reduce its greenhouse gas emissions. Such scenario are typically created with integrated assessment models that include a representation of the economy, and the energy, land-use, and industrial system. However, current climate change scenarios have a key weakness in that they typically focus on reaching specific climate goals in 2100 only. <br><br>This choice results in risky pathways that delay action and seemingly inevitably rely on large quantities of carbon-dioxide removal after mid-century. Here we propose a framework that more closely reflects the intentions of the UN Paris Agreement. It focusses on reaching a peak in global warming with either stabilisation or reversal thereafter. This approach provides a critical extension of the widely used Shared Socioecononomic Pathways (SSP) framework and reveals a more diverse picture: an inevitable transition period of aggressive near-term climate action to reach carbon neutrality can be followed by a variety of long-term states. It allows policymakers to explicitly consider near-term climate strategies in the context of intergenerational equity and long-term sustainability.</p>



2021 ◽  
Author(s):  
Jacob Waslander ◽  
Julie Bos ◽  
Yili Wu

This paper focuses on answering the following question: how can a private sector bank—one that has already committed to shifting its business model towards net-zero emissions—change its client engagement strategy and update its offerings? This paper analyzes action already taken by banks and identifies additional steps private sector banks should take to align their business model with the Paris Agreement (greenhouse gas mitigation objective) and cater to their clients’ needs in a manner that fosters a net-zero transition.



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