Incremental improvements of 2030 targets insufficient to achieve the Paris Agreement goals

Andreas Geiges,Carl-Friedrich Schleussner,Paola Yanguas Parra,William Hare,Michiel Schaeffer,Marina Andrijevic,Alexander Nauels,Peter Pfleiderer

doi:10.5194/esd-11-697-2020

Abstract

Abstract. Current global mitigation ambition up to 2030 under the Paris Agreement, reflected in the National Determined Contributions (NDCs), is insufficient to achieve the agreement's 1.5 ∘C long-term temperature limit. As governments are preparing new and updated NDCs for 2020, the question as to how much collective improvement is achieved is a pivotal one for the credibility of the international climate regime. The recent Special Report on Global Warming of 1.5 ∘C by the Intergovernmental Panel on Climate Change has assessed a wide range of scenarios that achieve the 1.5 ∘C limit. Those pathways are characterised by a substantial increase in near-term action and total greenhouse gas (GHG) emission levels about 50 % lower than what is implied by current NDCs. Here we assess the outcomes of different scenarios of NDC updating that fall short of achieving this 1.5 ∘C benchmark. We find that incremental improvements in reduction targets, even if achieved globally, are insufficient to align collective ambition with the goals of the Paris Agreement. We provide estimates for global mean temperature increase by 2100 for different incremental NDC update scenarios and illustrate climate impacts under those median scenarios for extreme temperature, long-term sea-level rise and economic damages for the most vulnerable countries. Under the assumption of maintaining ambition as reflected in current NDCs up to 2100 and beyond, we project a reduction in the gross domestic product (GDP) in tropical countries of around 60 % compared to a no-climate-change scenario and median long-term sea-level rise of close to 2 m in 2300. About half of these impacts can be avoided by limiting warming to 1.5 ∘C or below. Scenarios of more incremental NDC improvements do not lead to comparable reductions in climate impacts. An increase in aggregated NDC ambition of big emitters by 33 % in 2030 does not reduce presented climate impacts by more than about half compared to limiting warming to 1.5 ∘C. Our results underscore that a transformational increase in 2030 ambition is required to achieve the goals of the Paris Agreement and avoid the worst impacts of climate change.

Highlights

Under the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC), governments have committed to holding temperature increase well below 2 ◦C above pre-industrial levels and to pursue efforts to limit to 1.5 ◦C (UNFCCC, 2015)
In order to illustrate the implications of different temperature trajectories, we extend our analysis with additional climate impacts for three selected pathways: the current Nationally Determined Contributions (NDCs) pathway as reference (NDC), a selected gradual improvement scenario for the big emitters (CAT countries) with a reduction in greenhouse gas (GHG) emissions by 33 % (BE33) and a 1.5 ◦C scenario based on SSP1-RCP1.9 (Rogelj et al, 2018b) (1.5 ◦C)
Applying a consistent model setup, our slightly more optimistic current NDC reference scenarios used here would lead to a warming reduction of about 0.2 ◦C, implied by a reduction in 2030 GHG emission levels of about 1.5 Gt CO2 eq compared to the 2018 Climate Action Tracker (CAT) pathway

Summary

Introduction

Under the Paris Agreement of the United Nations Framework Convention on Climate Change (UNFCCC), governments have committed to holding temperature increase well below 2 ◦C above pre-industrial levels and to pursue efforts to limit to 1.5 ◦C (UNFCCC, 2015). The IPCC further stressed that “rapid and far-reaching transitions” are required to achieve those emissions reductions and highlighted the importance of “fundamental societal and systems transitions and transformations” in helping to achieve the 1.5 ◦C limit. In this context, it is important to emphasise that the scientific underpinning of the Paris Agreement temperature goal is linked to robust assessments of risks and impacts of climate change that would be avoided by achieving it (Schleussner et al, 2016b; Pfleiderer et al, 2018)

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Conclusion