An emission pathway classification reflecting the Paris Agreement climate objectives

Abstract

The 2015 Paris Agreement sets the objectives of global climate ambition as expressed in its long-term temperature goal and mitigation goal. The scientific community has explored the characteristics of greenhouse gas emission reduction pathways in line with the Paris Agreement. However, when categorizing such pathways, the focus has been put on the temperature outcome and not on emission reduction objectives. Here we propose a pathway classification that aims to comprehensively reflect the climate criteria set out in the Paris Agreement. We show how such an approach allows for a fully consistent interpretation of the Agreement. For Paris Agreement compatible pathways, we report net zero CO2 and greenhouse gas emissions around 2050 and 2065, respectively. We illustrate how pathway design criteria not rooted in the Paris Agreement, such as the 2100 temperature level, result in scenario outcomes wherein about 6 - 24% higher deployment (interquartile range) of carbon dioxide removal is observed.

Overcoming global inequality is critical for land-based mitigation in line with the Paris Agreement

“…To a large extent, GHG emission reductions in such transformation pathways depend on the assumption of a globally coordinated GHG emission pricing scheme across different sectors including energy, industry, transport, buildings, and AFOLU 4 , 5 . Some transformation pathways go beyond meeting the Paris Agreement climate objectives 6 and aim to maximize co-benefits with the broader United Nations Sustainable Development Goals (SDG) agenda 7 , 8 . In such sustainable transformation pathways, global GHG emission pricing is often complemented with global-scale inclusive socio-economic development (a convergence of all countries towards, e.g., the same demographic profiles, lower food waste levels, and healthy diets) and sustainable land-use practices (e.g., ecosystem protection and efficiency improvements) 7 , 8 .…”

“…Moreover, the Russian invasion of Ukraine might negatively affect food security, and in consequence political stability, in countries with limited coping capacity, especially in the Middle East and Africa 18 . In light of the closing window for reaching the global 1.5 °C target 11 , it seems highly relevant to study how (in)compatible AFOLU GHG emissions in a world of deepening inequalities would be with the Paris Agreement climate objectives 6 . Likewise, a forward-looking analysis of expanding mitigation options from high-income regions to the global level can provide insights on the most effective options for AFOLU emission reduction in low- and middle-income regions under consideration of co-benefits and trade-offs with other SDGs.…”

Assessing the size and uncertainty of remaining carbon budgets

“…Many approaches to equitable international climate action involve estimating the global RCB and dividing it among nations according to various priniciples of equity [4,5]. However the RCB for the Paris-relevant temperature targets (generally interpreted as a 50% chance of keeping global warming below 1.5 • C and anywhere from a 66%-90% chance of 2.0 • C [6]) are small compared to the uncertainty in their values, which makes their use challenging.…”

Policy guidance and pitfalls aligning IPCC scenarios to national land emissions inventories

“…In this manuscript we focus on two categories of scenarios: "C1" and "C3". "C1" scenarios can be considered consistent with the Paris Agreement's 1.5 °C long-term temperature goal as outlined in its Article 2 (17), although arguments have been made that further delineation should be made into scenarios that do and do not achieve net-zero CO2 emissions in order to better reflect its Article 4 (18). We additionally highlight outcomes from 2 °C, or "C3", scenarios given their historic policy relevance, their capability to show progress towards 1.5 °C, and their use in examining climate impacts beyond what is envisioned by the Paris Agreement.…”