Remaining Carbon Budget — Who Spends It & What It Costs
The global carbon budget is the total cumulative amount of CO₂ humanity can emit while keeping warming below a given temperature threshold. Since the Industrial Revolution humanity has already burned through ~2390 Gt CO₂ — roughly 90.5% of the pre-industrial carbon budget consistent with 1.5°C. What remains is finite and contested: ~1150 Gt for the 2°C threshold (from Jan 2024). At 57.4 Gt/yr, that runs out in 20.0 years — around 2044. The question of who spends it — which countries, which companies, and at what consequence — is one of the defining geopolitical and financial questions of this century.
1150 Gt
Remaining 2°C budget (Jan 2024, 67% prob.) — IPCC AR6. At current pace: exhausted ~2044
250 Gt
Remaining 1.5°C budget (50% prob.) — effectively already overshoot territory; requires CDR to return
57.4 Gt/yr
Current global annual emissions (2023) — Global Carbon Project 2023; fossil fuels + LULUCF
20.0
Years to exhaust 2°C budget at current emissions pace (no action scenario)
90.5%
Share of total 1.5°C budget already spent since 1850 — only ~10% remains for 1.5°C pathway
2390 Gt
Cumulative CO₂ emitted since 1850 — IPCC AR6; primarily by industrial economies (US + EU = ~50%)
Remaining Carbon Budget — 2°C vs 1.5°C (1990–2024)
The 1.5°C budget (dashed) crossed zero around 2017 at a 67% probability threshold. The 2°C budget (solid) has ~1150 Gt remaining. Negative 1.5°C values represent the "carbon debt" that must be repaid via carbon dioxide removal (CDR) to return to 1.5°C.
Source: IPCC AR6 WGI Table SPM.2 (2021); Global Carbon Project 2023; Carbon Brief analysis 2023.
Emissions by Sector — Current vs NZE 2030 Target (Gt CO₂e/yr)
Energy and Industry together account for 58% of global emissions. Transport at 16% is the fastest-growing sector in developing economies. Agriculture (18%) is structurally hard to decarbonise — methane from livestock and rice paddies has no zero-cost abatement pathway.
Source: IEA World Energy Outlook 2024; IPCC AR6 WG3 Chapter 2; Global Carbon Project 2023.
The budget is not an abstraction — it is a physical constraint. Every Gt of CO₂ emitted moves the global thermostat by approximately 0.45°C per trillion tonnes (TtCO₂). The budget is calculated from the known relationship between cumulative CO₂ and global mean surface temperature (GMST). The 2°C budget of ~1150 Gt from 2024 is consistent with a 67% probability of staying below 2°C above pre-industrial levels. This is not a policy target — it is physics. Once the budget is spent, additional warming is locked in regardless of future action, except via active CDR (carbon dioxide removal), which does not currently exist at gigatonne scale.
The 1.5°C budget was effectively exhausted around 2017. On a 67% probability basis, the remaining 1.5°C budget as of January 2024 was approximately 250 Gt (IPCC AR6 central estimate). At 57+ Gt/yr, this represents ~4 years of emissions. The IPCC SR1.5 (2018) already flagged this urgency. Returning to 1.5°C now requires net negative emissions — removing more CO₂ than is emitted globally. No credible scenario achieves this without massive deployment of CDR technologies (DACCS, BECCS, reforestation) that do not yet exist at the required scale.
Global Emissions Trajectories by Policy Scenario (Gt CO₂e/yr, 2024–2050)
Source: UNEP Emissions Gap Report 2023; Climate Action Tracker Current Policy Projections 2024; IEA NZE 2050 Scenario 2024; IPCC AR6 C1 scenario family (1.5°C with low/no overshoot).
Scenario Comparison — Key Metrics
| Scenario | Emissions 2030 | Implied Warming | 2°C Budget Exhausted | Cumul. 2024–2040 |
|---|
Current national policies imply ~3.2°C of warming — well past the 2°C budget exhaustion point (~2041). Even full implementation of all current NDCs (nationally determined contributions) only buys 7 additional years before the 2°C budget is spent. Only trajectories consistent with IEA NZE or the IPCC 1.5°C pathway avoid exhausting the 2°C budget entirely.
The "NDC gap" — the difference between what countries have pledged and what science requires — corresponds to approximately 20–23 Gt CO₂e/yr by 2030. Closing this gap in six years would require the largest structural transformation in energy history.
Source: UNEP Emissions Gap Report 2023; Climate Action Tracker 2024; IEA WEO 2024.
Share of Remaining 2°C Budget by Country (%, current policy projection)
Source: Global Carbon Project 2023; Climate Action Tracker 2024; IEA World Energy Outlook 2024; IPCC AR6 WGI.
Country Emissions Profile — 2024 vs 2030 (Current Policy vs NZE, Gt/yr)
Source: Global Carbon Project 2023; Climate Action Tracker 2024 national assessments; IEA NZE 2050 sectoral pathways.
Country Projections — NDC Strength, Budget Share & Economic Consequences
| Country | Emissions 2024 (Gt) | Emissions 2030 (Current) | Share of 2°C Budget | Net Zero Target | NDC Strength | GDP Loss @ 3°C | Stranded Assets ($B) |
|---|
Country Risk Narrative
Click a row above to see the country's consequence narrative, key climate risks, and source data.
Company Stranded Asset Exposure — 1.5°C vs 2°C Scenario ($B)
Source: Carbon Tracker Initiative 2022/2023; IEA World Energy Outlook NZE 2024; IRENA 2023; company annual reports.
Scope 3 Reserve Emissions — Share of 1.5°C Budget (% by company)
Scope 3 reserve emissions = CO₂ embedded in a company's proved fossil fuel reserves if fully combusted. Even the top 10 companies control reserves equivalent to ~60% of the remaining 1.5°C budget.
Source: Carbon Tracker Initiative 2023; Rystad Energy 2023; CDP 2023; company annual reports (SEC 10-K / 20-F proved reserve disclosures).
Physical Risk — 2°C Scenario
Global GDP Loss
-2.6%
Sea Level Rise by 2100
0.43 m
Additional Population Under Water Stress
+14%
Additional Extreme Heat Days (Tropics/yr)
+20 days
Vertebrate Biodiversity Loss
8%
Food System Risk
Moderate — tropical cereal yield declines 5–15%; temperate gains partially offset
Physical Risk — 3°C Scenario (Current Policies)
Global GDP Loss
-5.1%
Sea Level Rise by 2100
0.73 m
Additional Population Under Water Stress
+32%
Additional Extreme Heat Days (Tropics/yr)
+60 days
Vertebrate Biodiversity Loss
18%
Food System Risk
Severe — simultaneous crop failures in 3+ breadbaskets become annual events
Transition Risk — Net Zero by 2050 (IEA NZE)
Globally stranded fossil fuel assets$14.0T
Oil & gas demand reduction by 2040-55%
Coal demand reduction by 2030-75%
GDP gain from clean energy transition$5.2T
Fossil fuel job displacement5.5M jobs
Clean energy jobs created38.0M jobs
Net job creation ratio6.9:1
The transition creates more jobs than it destroys — globally a 6.9:1 ratio. But the jobs destroyed (coal miners, oil workers) are in different communities and require different skills than the jobs created (solar installers, EV technicians, grid engineers). Without active industrial policy, the transition imposes severe localised economic costs — Appalachia, the Ruhr Valley, Jharkhand — even while generating net global welfare gains.
Source: IEA WEO NZE 2024; IRENA World Energy Transition Outlook 2024; Carbon Tracker 2023 global stranded assets.
Climate Litigation — Global Case Count & Landmark Rulings
Source: Sabin Center for Climate Change Law (Columbia) — Global Climate Change Litigation Database 2023; UNEP Climate Litigation Report 2023. Growth rate ~17%/yr.
Landmark Cases
Milieudefensie v Shell
Outcome: 45% Scope 1–3 reduction ordered; Shell appealed; Hague Court of Appeals 2024 partially upheld
First court order mandating corporate Scope 3 emissions reduction
Held v Montana
Outcome: Montana's MEPA policy struck down — state must consider climate impacts in energy permitting
First US court ruling on state constitutional right to clean environment linked to climate
Urgenda v Netherlands
Outcome: Government ordered to cut emissions 25% by 2020 vs 1990 levels
First successful national government climate case; template for 15 subsequent cases
Torres Strait Islanders v Australia
Outcome: Australia found to have violated human rights by inadequate climate action
First UN body finding on climate-human rights nexus; opens ICCPR Article 17 pathway
ClientEarth v Shell Board
Outcome: UK High Court dismissed; but legal theory — directors breached duty by inadequate climate planning — advanced
Director liability theory; likely to be re-litigated as TNFD/ISSB reporting becomes mandatory