WHAT IS CLIMATE OVERSHOOT? UNEP ROADMAP

Why In News?

The United Nations Environment Programme (UNEP) has released the 'Limiting Overshoot' report, warning of irreversible tipping points if global warming exceeds 1.5°C.

What is Climate Overshoot?

Climate overshoot refers to a scenario where global average surface temperatures temporarily rise above a targeted threshold—specifically 1.5°C above pre-industrial levels—before peaking and declining back down.

• Paris Agreement Benchmark: Under Article 2 of the Paris Agreement, nations committed to holding global warming well below 2°C while pursuing efforts to limit temperature rise to 1.5°C to avert catastrophic impacts.

• Three-Stage Overshoot Trajectory: Follows a modeled pathway involving: (1) temperature exceedance beyond 1.5°C, (2) reaching a peak warming ceiling, and (3) a gradual secular decline driven by net-negative greenhouse gas emissions.

• Heavy Reliance on Unproven Carbon Dioxide Removal (CDR): Returning temperatures back below 1.5°C requires deploying massive carbon dioxide removal technologies (such as direct air capture and bioenergy with carbon capture) to extract historical emissions from the atmosphere.

• Categorisation of Low vs  High Overshoot: Intergovernmental Panel on Climate Change (IPCC) models distinguish between "low overshoot" (temperatures temporarily exceeding 1.5°C by up to 0.1°C–0.2°C) and "high overshoot" (temperatures exceeding 1.5°C by 0.3°C–0.5°C or more).

Why is 1.5°C Overshoot Dangerous?

Irreversible Ecological Tipping Points: Even if temperatures are lowered, temporary peak warming can trigger irreversible tipping elements—including the catastrophic melting of the Greenland and West Antarctic ice sheets, Amazon dieback, and coral reef extinction.

Breaching Biocultural Adaptation Limits: Higher peak warming pushes human settlements, agricultural zones, and ecosystems beyond their physical coping capacities, where adaptation becomes impossible regardless of financial investment.

Acceleration of Loss and Damage: Prolonged periods of elevated temperatures multiply extreme weather disasters—such as super-cyclones, flash droughts, and catastrophic glacial lake outburst floods (GLOFs)—inflicting deep economic damage on developing states.

Release of Natural Feedback Emissions: Excessive warming thaws Arctic permafrost and destabilizes marine methane hydrates, releasing gigatons of stored greenhouse gases that further accelerate global warming beyond human control.

Permanent Threat of Sea-Level Rise: Thermal expansion of the oceans and deep continental ice-sheet melting operate on millennial lag cycles, meaning sea levels will continue rising for centuries even if atmospheric temperatures cool back down.

What Does UNEP Recommend?

Strictly Limiting Peak Temperature Warming: Climate policy must minimize the maximum temperature reached above 1.5°C, ensuring warming remains as close as possible to the target to avoid triggering threshold points.

Minimising the Duration of Overshoot: The temporal window of temperature exceedance must be compressed into the shortest possible duration, ideally limited to a few decades rather than centuries.

Aggressive, Frontloaded Emissions Reductions: Deep, immediate greenhouse gas cuts across all sectors remain the primary defense; speculative future carbon removal must not substitute for current fossil fuel phase-outs.

Simultaneous Scaling of Global Adaptation: Governments must urgently scale up investments in early warning systems, climate-resilient agriculture, and flood defences to manage unavoidable climate impacts during the overshoot phase.

Immediate Phase-Out of Inefficient Fossil Subsidies: Direct public capital away from oil, gas, and coal exploration toward clean energy systems and equitable socio-economic safety nets.

Key Policy Priorities

• Accelerating the Global Renewable Energy Transition: Tripling global renewable electricity capacity (solar, wind, storage) to 11,000 GW by 2030, in line with commitments made at COP28.

• Doubling the Global Rate of Energy Efficiency: Mandating resource-efficiency standards in industrial manufacturing, building architecture, and electrified transport networks.

• Responsible Deployment of Carbon Dioxide Removal: Developing verifiable, socially equitable CDR methods (such as afforestation, biochar, and direct air capture) strictly as a secondary measure to tackle residual emissions.

• Constructing Climate-Proof Resilient Infrastructure: Building urban drainage, transport networks, and coastal sea-walls engineered to withstand extreme 1-in-100-year weather anomalies.

• Reforming Global Climate Finance Architectures: Delivering predictable, grant-based adaptation funding and affordable technology transfers from industrialized nations to the Global South.

Source: THEHINDU