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Setu @setupelz.bsky.social · 28/09/2026

The cost gap would reduce if you imagine capture costs to fall faster, but the rate at which this channel (alone) could address carbon debt this century is a function of scale-up (already steep here) and injection rate limits (conservative here, reaching / holding at 6Gt). Paper on this out soon..

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Setu @setupelz.bsky.social · 28/09/2026

Our main cost-effective source scenario is close to, though not the same as, the ScenarioMIP-CMIP7 Low marker from the same model family. The interactive scenario explorer places them side by side. In Western Europe, e.g. every lowest-feasible variant phases out gas and oil faster..

Screenshot of the paper's online explorer for Western Europe under a 2 °C budget: coal, oil and gas supply from 2020 to 2100, in EJ per year. Four fair-share variants at lowest-feasible transfers (ECPC 2015, CAPC 1990, CAPC 2015 and ECPC 1990, blue lines) are compared with the cost-effective source pathway (thick black line) and the ScenarioMIP-CMIP7 Low marker from the same model family (dotted teal line). Coal falls to near zero by about 2050 in all pathways. The fair-share variants phase out oil and especially gas faster than both the source pathway and the CMIP7 Low marker.

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Setu @setupelz.bsky.social · 28/09/2026

..even when cooperation is restricted to financing novel CDR with geological storage, we see roughly two-thirds of higher-responsibility regions' carbon debt is avoided through gross emission cuts. Each tonne via CDR+geo costs roughly ten times what it would through direct mitigation (excl. LULUCF).

Figure 4a and 4b from the paper, ECPC 2015 case under a 2 °C budget. a: cumulative change from the source scenario in net CO2, gross CO2, BECCS and DACCS for the World, higher-responsibility and lower-responsibility regions, comparing cooperation through transfers for any mitigation with transfers restricted to carbon removal. Restricting cooperation to removal deepens gross emission cuts in higher-responsibility regions. b: stacked bars showing how the higher-responsibility regions' carbon debt is cleared, by cooperation scope (all mitigation or removal only) and transfer level (unlimited or lowest-feasible). With transfers for any mitigation, transfers cover most of it; with transfers restricted to removal, roughly two-thirds is met by domestic emission reductions.

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Setu @setupelz.bsky.social · 28/09/2026

Globally, collective fossil exit accelerates: in 2040, fossil energy falls 3-21% below the cost-effective source scenario. At the same time global consumption losses rise somewhat, though these are progressively distributed - lower-responsibility regions gain relative to the cost-effective pathway.

Figure 3a and 3b from the paper, 2 °C budget. a: cumulative change in consumption from 2026 to 2100 against a no-new-policy scenario (percent, net present value) for each fair-share allocation approach, shown for the World, higher-responsibility and lower-responsibility regions, with the cost-effective source scenario as crosses. World changes stay around one percent; lower-responsibility regions gain under the fair-share variants while higher-responsibility regions lose. b: the trade-off for higher-responsibility regions between additional domestic CO2 cuts relative to the source scenario and interregional transfers. Each line runs from unlimited transfers (up to about 40 trillion USD, no extra domestic cuts) to lowest-feasible transfers (a few trillion USD, with up to about 270 Gt CO2 of extra domestic cuts).

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Setu @setupelz.bsky.social · 28/09/2026

Holding finance to the lowest feasible (read: model feasibility) level redistributes implementation effort. Higher-responsibility regions reduce gross emissions faster, lower-responsibility regions gain room for a more gradual transition, and the global outcome holds (!!!! this is important).

Figure 2a from the paper: line charts of net CO2 (top row) and gross CO2 (bottom row) from 2030 to 2100, as percentage change from 2020, for the World, higher-responsibility regions and lower-responsibility regions. Coloured lines are six fair-share allocation approaches (ECPC and CAPC, with 1990, 2015 and 2025 start years, plus a delayed-cooperation case) at lowest-feasible transfers; the black line is the cost-effective source scenario, under a 2 °C budget (SSP2). At World level the lines almost overlap. Higher-responsibility regions reduce emissions faster than in the source scenario, and lower-responsibility regions reduce them more gradually.

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Setu @setupelz.bsky.social · 28/09/2026

Interregional cooperation is the central element. Regions meet their fair share at home or by financing mitigation elsewhere. Two variants bound the space: 'unlimited transfers' and a new 'lowest-feasible transfers' variant, the least interregional finance with which the model still solves.

Figure 1b from the paper: two schematic charts of the solution space. Top: global mitigation cost plotted against how effort is distributed between regions. The source scenario and the 'unlimited transfers' variant sit at the least-cost end; the 'lowest-feasible transfers' variant sits at the higher-cost end. Bottom: cumulative CO2 emissions over time. Unlimited transfers follow the same trajectory as the source scenario, while lowest-feasible transfers take a different path to the same end-of-century cumulative emissions.

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Setu @setupelz.bsky.social · 28/09/2026

..so, we developed an approach to integrate principle-based fair shares directly into the IAM scenario generation process. The global climate outcome of the cost-effective scenario is preserved, while its regional implementation is redistributed. The framework can be applied to *any* scenario.

Figure 1a from the paper: a diagram of how fair-share variants are derived from an existing mitigation pathway in four steps. 1) Assess the source scenario's emissions. 2) Allocate each region an emissions budget under a fairness principle; emissions above that allocation are the region's carbon debt. 3) Set cooperation mechanisms, so the debt is met through interregional transfers or additional domestic effort. 4) Solve the fair-share variant. A flow chart below shows covered emissions passing through regional allocations and a cooperation mechanism into new pathways, while excluded emissions follow the source scenario's carbon price.

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Setu @setupelz.bsky.social · 28/09/2026

Two years plus in the making... our paper building fair effort sharing directly into how integrated assessment model (IAM) scenarios are generated is out in Environmental Research Letters🧵 @iopp-environment.bsky.social @iiasa.ac.at doi.org/10.1088/1748-9326/aea34d

First page of the article 'Equitable cooperation deepens the solution space for high ambition pathways' by Setu Pelz and eleven co-authors, published open access in Environmental Research Letters 21 (2026) 184019 on 18 September 2026. The page shows the author list, affiliations and the abstract.

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Setu @setupelz.bsky.social · 23/11/2025

Call for abstracts - EGU 2026 session ITS3.6/ERE6.5 on justice and social science and humanities (SSH) integration in climate modelling. We invite work linking SSH and IAMs on justice, labour, needs, power, governance and Global South perspectives. Submit (by 15 Jan 2026) www.egu26.eu/session/57677

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Setu @setupelz.bsky.social · 31/05/2025

Our analysis identifies critical regions where this ‘gap’ is most acute, notably coastal West Africa, Ethiopian highlands, and the Great Lakes region encompassing Kenya, Tanzania, Uganda, Rwanda, Burundi, and the DRC.

A figure describing unelectrified populations by Urban-Rural Catchment Area (URCA) categories. The x-axis is ordinal, describing the URCA categories from within the urban core to the hinterlands. The y-axis is the percent of total unelectrified. The points are coloured by focus countries, with all others left as grey. The size of the points reflect the absolute unelectrified population. We can see the majority of the unelectrified population is found in categories that reflect at most 1 hour travel time to medium- and large cities.

Choropleth maps of the DRC and Ethiopia, describing the unelectrified population (people / square km) and highlighting major cities.

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Setu @setupelz.bsky.social · 31/05/2025

We combine the Urban Rural Catchment Area (URCA) framework with satellite derived spatial electrification datasets to highlight spatial patterns in electricity access gaps.

A figure describing the workflow from data preprocessing of various spatial datasets to their combination identifying the unelectrified by URCA category across all countries in Sub-Saharan Africa.

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Setu @setupelz.bsky.social · 31/05/2025

Urbanization trends are reshaping human settlement patterns and energy needs. Our recent (open access) work, led by Jessica Kersey and Samuel Miles, explores these dynamics across countries in Sub-Saharan Africa 🧵

A map of Sub-Saharan Africa, visualising the unelectrified population using circles sized by population (1000 people / 20 km) and coloured by electrification rate. The inset plots show the Gulf of Guinea, the Ethiopian Highlands and the African Great Lakes region.

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Setu @setupelz.bsky.social · 25/03/2025

On net-negative removals: we examine the physical implications of translating carbon debts into drawdown obligations. We find some evidence of long-term temperature equivalence, but.. high overshoot remains risky. See: www.nature.com/articles/s41... Avoiding the debt in the first place is better.

Figure S15 – Relationship between TCRE_up and TCRE_down in the 841 FaIR ensemble members for C1 scenarios. Below the 1:1 line (red shading), carbon removals are less effective at cooling than emissions are at warming. The blue shaded region above the 1:1 line shows the opposite. Points are coloured according to the underlying TCREup.

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Setu @setupelz.bsky.social · 25/03/2025

Second, we look beyond emissions accounting, to highlight the dual burden transferred to younger generations: 📉 Per-capita carbon drawdown obligations 🌡️ Years of life exposed to 1-in-100-year heatwaves These diverge sharply across regions and grow worse under a pessimistic current policy scenario.

Increased extreme heatwave exposure and carbon drawdown obligations under current policies and pledges. Increase in years of life exposed to extreme (1-in-100-year) heatwaves (primary y-axis) relative to the 1.5 °C reference scenario (IMP-REN, AR6), for all cohorts born between 1960 and 2020 (x-axis). The shaded areas reflect the 33rd and 66th percentile across all global climate model runs and TRQs (Methods). The annual equal per capita drawdown obligation to address regional responsibility for scenario overshoot by the year 2100 (starting in 2025) is shown on the secondary y-axis. This refers to an equal cumulative per capita allocation of the total carbon budget from the year 1990, composed of global CO2 emissions from fossil fuel and industrial processes (CO2-FFI) between the years 1990 and 2023 and an estimated 1.5 °C RCB (50% chance) from the year 2023.

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Setu @setupelz.bsky.social · 25/03/2025

We demonstrate the relevance of this measure for guiding contemporary climate action by applying it to two scenarios of possible futures: Current Policies (¬3C), and Announced Pledges (¬1.8C). First, we illustrate accrued debts and responsibility for overshoot in either case...

Differentiated carbon debt accrual and overshoot responsibilities under current policies and pledges. (A) Estimated median climate overshoot under the assessed scenarios (33rd to 66th GMT anomaly quantiles as ribbon). (B) Emissions pathways, carbon debt accrual and corresponding overshoot responsibilities, separating regions that accrue carbon debt by 2030 from those that accrue carbon debt later (see grouping in the caption). This considers an equal cumulative per capita allocation of the total carbon budget from the year 1990, composed of global CO2 emissions from fossil fuel and industrial processes (CO2-FFI) between the years 1990 and 2023 and an estimated 1.5 °C RCB (50% chance) from the year 2023.

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Setu @setupelz.bsky.social · 25/03/2025

We illustrate this using the AR6 scenarios database: Some regions always accrue debt due to past emissions. Some if they delay net-zero CO2 until late this century. Some only if they push net-zero CO2 past 2100. Each case implies different responsibilities for drawdown—and for overshoot harms.

Assessing carbon debts accrued under varying regional net-zero CO2-FFI timings. Density plots describe scenario distributions of regional net-zero carbon debt accrual grouped by regional net-zero CO2-FFI timings in the AR6 scenarios database, subset to reflect a maximum 2090 regional net-zero CO2-FFI timing group. Circular shapes indicate the median net-zero carbon debt within each timing group.

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Setu @setupelz.bsky.social · 25/03/2025

Net-zero carbon debt compares a region’s cumulative CO₂ emissions (past + projected to net-zero) against its fair share of the 1.5°C budget. Any excess is debt: emissions that need to be drawn down later, making overshoot worse and harder to reverse. (for a discussion on fair shares - see link👇)

The persistent accrual of net-zero carbon debt. Regional net-zero carbon debt is quantified by subtracting (i) past and (ii) future cumulative carbon emissions from (iii) a fair allocation of the total carbon budget comprising both a RCB and past global carbon emissions as desired.

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Setu @setupelz.bsky.social · 27/01/2025

Comparing our ‘fair warming’ budgets to deepest available domestic reduction (DADR) pathways shows that high domestic ambition is unlikely to be sufficient for many. This underscores a major challenge: the need to address expected breaches through international cooperation (more on this soon...).

Figure comparing remaining CO2-we budgets with deepest available domestic reduction (DADR) pathways.

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Setu @setupelz.bsky.social · 27/01/2025

We consider three principles: polluter pays, ability to pay, and beneficiary pays, and test how these shift each country’s ‘fair warming’ budget. We also look at different start years for accounting. No matter how you slice it, most developed countries end up with zero or -ve remaining budgets.

Figure showing differences in remaining national CO2-we budgets under different interpretations of principles.

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Setu @setupelz.bsky.social · 27/01/2025

Why is this work necessary? Well, considering non-CO₂ emissions (like methane) builds a more accurate picture of each country’s warming contribution and enables a better comparison with future pathways. However, there are extensive debates on how to account for these gasses, which we navigate here.

Figure showing differences in remaining national CO2-we budgets when accounting for different emissions sources.

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Setu @setupelz.bsky.social · 16/01/2025

We explain why these are important, using examples from contemporary NDCs that mention fairness or equity but remain opaque in their operationalisations. To show their application in practice, we conduct a case study for the EU.

Table describing the outcomes of the EU case study.

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Setu @setupelz.bsky.social · 16/01/2025

The four common entry points we identify and discuss are: 1️⃣Foundational principles – which principles are important? 2️⃣Allocation quantity – what are we allocating exactly? 3️⃣Allocation approach – how is it shared out? 4️⃣Indicators – what data do we need? (and, what does this mean for all others).

Table describing the four entry points listed in the post.

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Setu @setupelz.bsky.social · 29/11/2024

Does anyone have a list of all national (state-owned) oil and gas companies and the country to which they belong? Is this reasonably complete en.wikipedia.org/wiki/Categor... ?

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Setu @setupelz.bsky.social · 16/11/2024

The judgement has constitutional law implications as relates to climate, but the court references India’s obligations under their NDCs to the PA (they also refer to the UNFCCC). For a better discussion, see: www.theindiaforum.in/climate-chan...

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