While ten years have passed since the Paris Agreement, global efforts to reduce emissions are still lacking, with recent UN projections indicating that the world is on course for a temperature rise of 3.1°C by 2100 – well above the 1.5°C limit, with potentially devastating consequences.
As the World Resources Institute’s Clea Schumer, Sophie Boehm, Kirian Mischke-Reeds, and Cynthia Elliott note, this year marks a “prime opportunity to change course”, as countries put forward their new nationally determined contributions (NDCs) ahead of COP30 in November 2025.
These NDCs need to reflect a country’s ‘highest possible ambition’, in line with the requirements of the Paris Agreement, as well as its ‘common but differentiated responsibilities and respective capabilities’.
In a recent article, What Would Ambitious Climate Commitments Look Like for the World’s Top Emitters? It’s Complicated, Schumer, Boehm, Mischke-Reeds and Elliott examined five different approaches that countries can take when setting their national emissions reduction targets.
1. 1.5°C-Aligned, Least-Cost Pathways
This approach uses economic modelling to map out the most affordable route to meeting climate goals, utilising sources such as Intergovernmental Panel on Climate Change (IPCC) data.
“While some global climate models can now generate least-cost pathways for major emitters, others still lack country-level data,” the authors state. “They instead simulate global or regional scenarios that must be downscaled to the national level.”
2. 1.5°C-Aligned, Fair-Share Pathways
Fair-share pathways look beyond economic efficiency, incorporating historical emissions, economic capability, and per capita equality to distribute global climate responsibilities more equitably.
While least-cost pathways can assign some developing countries disproportionate responsibility for reducing GHG emissions, “fair-share perspectives attempt to address such limitations – for instance, by considering historical responsibility for total emissions, economic capacity and equality in per capita emissions – when determining each country’s contribution to limiting warming to 1.5 degrees C,” the authors state.
3. National Modelled Pathways to Net Zero
Nationally modelled pathways to net zero illustrate how individual countries can reach their own climate targets by mid-century – reflecting a particular country’s unique mix of policies, technologies, and economic conditions.
“These scenarios focus not on determining an individual nation’s contribution to the global goal of limiting warming to 1.5 degrees C, but rather on achieving that country’s pledge to reach net-zero emissions,” the authors note. “They show how steeply emissions need to decline in 2030 and 2035 to stay on track to reach net zero – typically around mid-century for most countries.”
4. Linear Trajectories to Net Zero
Linear trajectories to net zero are also gaining traction among some governments – involving, essentially, the drawing of a straight line to a net-zero target by 2050, and ensuring that their 2030 and 2035 targets are either on this line or below it.
According to the authors, “the devil is in the details, as the starting point governments select may significantly impact the steepness of the line; the steeper the line, the more ambitious the national benchmarks will be.”
5. Bottom-Up, Feasibility-Focused Modelling
Other models prioritise what is realistically achievable in each country based on granular, bottom-up analysis. This type of feasibility-focused approach uses national data to explore what’s technically and politically possible given current infrastructure, economic development goals, and policy environments; such as the effect that a carbon tax might have on GHG emissions, or what the impact of specific climate change mitigation efforts would have.
“These scenarios may end up charting pathways to net-zero emissions or show that deep GHG emissions cuts in line with 1.5°C-aligned, least-cost pathways are feasible, but these end goals are not inputs to the modelling,” the authors state. Read more here.
Visit the World Resources Institute’s Climate Tracker for details on what countries have submitted NDCs to date.
