Context: The United Nations Environment Programme (UNEP) released a spotlight report titled “Limiting Overshoot: Navigating Exceedance of 1.5°C and Pathways Towards Return.”
- The report highlights that breaching the 5°C warming limit is now unavoidable in the near term, outlining an “overshoot, peak, and decline” framework to restore climate stability by 2100.
About UNEP Limiting Overshoot Report:
What is the Overshoot Framework?
- An overshoot pathway refers to a scenario where global average surface temperatures temporarily exceed the internationally agreed target (1.5°C) before peaking and gradually declining back below the limit through sustained net-negative emissions and deep decarbonization.
Key Findings in the Report:
- 1.5°C Threshold Nearing: Human-induced warming is nearing 1.4°C, rising at ~0.25°C per decade. WMO estimates a 75% chance that the 2026–2030 average will exceed 1.5°C.
- Shrinking Carbon Budget: Only about 130 GtCO₂ remains from 2026 for a 50% chance of limiting warming to 1.5°C. At current emissions (~40 GtCO₂ annually), it could be exhausted in about three years.
- Projected Warming: Current policies point to ~2.6°C warming by 2100. Even full implementation of NDCs and net-zero pledges could still result in peak warming of ~1.8°C.
- Cost of Delay: Every five years of sustained high emissions adds ~0.1°C to peak warming; reversing it would require removing about 220 GtCO₂.
- Ecological Tipping Points: Overshoot could trigger irreversible changes, including Greenland and West Antarctic ice-sheet loss, AMOC weakening and Amazon dieback.
- Cryosphere & Sea-Level Risks: Mountain glaciers could lose over 25% of their mass by 2100. Every century above 1.5°C could lock in ~40 cm additional sea-level rise by 2300.
- Socio-Economic Disruptions: Food production could fall by up to 14% by 2050 without adequate adaptation, while severe coral bleaching is pushing reefs beyond adaptation limits.
- Four-Stage Overshoot Pathway: An overshoot pathway is not a single event but a multi-decadal sequence across four distinct stages: Exceedance, Plateau/Peak, Decline, and Stabilization.
Positives Highlighted in the Report:
- Large Mitigation Potential: Available measures across energy, agriculture, industry and transport could cut up to 41 GtCO₂e annually by 2035, with nearly half costing below $20/tCO₂e.
- Health Co-Benefits: Rapid fossil-fuel phase-out could reduce SO₂ and NOx by 60–80%, lowering respiratory diseases and healthcare costs.
- Methane Reduction: Cutting methane, responsible for ~0.5°C of warming, offers one of the fastest ways to reduce near-term peak warming.
- Adaptation Pays: In developing economies, $1 invested in climate-resilient infrastructure can avoid about $4 in losses.
- Stronger Legal Precedents: International judicial rulings have strengthened 1.5°C-based due-diligence obligations for mitigation and adaptation.
Challenges Identified:
- Debt & Fiscal Stress: Climate-vulnerable countries face higher borrowing costs and rising reconstruction debt, reducing funds available for resilience.
Example: Around 70% of SIDS exceed the 40%-of-GDP debt threshold after repeated climate disasters.
- Limits of Carbon Removal: Nature-based CDR faces saturation and wildfire risks, while DACCS and BECCS require significant energy, water and land.
Example: Novel technological CDR contributes less than 0.1% of conventional removals.
- Maladaptation: Poorly designed adaptation can worsen ecological and social vulnerabilities.
Example: About 45% of Bonn Challenge restoration pledges involve commercial monocultures, which store far less carbon than native forests and can worsen water stress.
- SIDS Habitability Crisis: Sea-level rise and saltwater intrusion threaten freshwater, territory and statehood even before complete submergence.
Example: Tuvalu and Kiribati face substantial locked-in sea-level rise.
- Heat & Labour Productivity: Rising humid heat threatens human health and outdoor work.
Example: Labour capacity in Ghana could fall 11% at 3°C warming, while heat stress could drive 60–70% of projected GDP losses in Sri Lanka by 2053.
Recommendations:
- Integrate Mitigation & Adaptation: Pursue both simultaneously rather than treating them as competing priorities.
- Accelerate Decarbonisation: Rapidly phase down fossil fuels, expand renewables and sharply reduce methane emissions.
- Regulate Carbon Removal: Establish strong MRV frameworks and ensure CDR complements, rather than replaces, direct emission cuts.
- Transform Adaptation: Adopt flexible, climate-responsive infrastructure, nexus governance and planned retreat where necessary.
- Strengthen Loss & Damage Finance: Scale up the UNFCCC Fund for Responding to Loss and Damage before worsening climate impacts widen financing needs.
Conclusion:
A temporary 1.5°C overshoot may be increasingly difficult to avoid, but its scale and duration still matter. Every fraction of warming prevented can reduce irreversible ecological and human losses. Rapid decarbonisation, transformational adaptation and stronger climate finance are essential to return the world towards a safer temperature pathway.
