Climate Overshoot: The Peak-and-Decline Pathway

Why in News?

On 2 September 2026, UNEP released Limiting Overshoot, assessing a multi-year exceedance of 1.5°C as likely and mapping an urgent peak-and-decline pathway.

• UNEP identifies overshoot, peak and decline as the best remaining pathway for limiting the magnitude and duration of exceedance and attempting a return below 1.5°C.
• Its most optimistic assessed scenario peaks at 1.8°C above pre-industrial levels; most other scenarios produce higher peaks, including some above 2°C.
• The report links every additional fraction of warming and year of exceedance to intensifying impacts, harder adaptation and a greater chance of crossing irreversible thresholds.
• It calls for immediate emissions cuts, stronger adaptation and carefully governed carbon dioxide removal, while rejecting removal as a replacement for mitigation.

• Overshoot does not amend the Paris Agreement: its Article 2 temperature aim remains well below 2°C while pursuing efforts to limit warming to 1.5°C.
• Policy can still shape the curve’s peak, duration and decline, which determine cumulative exposure, adaptation needs and the risk of lasting losses.

UPSC Relevance

Prelims Relevance

• Climate overshoot: a period when long-term global warming exceeds a target before potentially declining below it.
• The pathway has four stages: exceedance, peak, decline and stabilization.
• A single warm calendar year is not identical to a long-term warming threshold, which climate science assesses over longer periods.
• Net-zero balances emissions with removals; net-negative emissions remove more greenhouse gases than are emitted.
• CDR removes carbon dioxide from the atmosphere and stores it in biological, geological or other reservoirs.
• Mitigation reduces the cause of warming; adaptation reduces vulnerability and exposure to its effects.

Mains Relevance

GS Paper 3

• Climate mitigation, adaptation limits and disaster-risk reduction under an overshoot pathway
• Carbon dioxide removal, land competition, permanence and environmental integrity

GS Paper 2

• Climate justice, international cooperation and differentiated responsibility for limiting overshoot

Essay

• Climate policy must manage both avoidable risks and irreversible losses without allowing an emergency pathway to weaken the original goal.

Background and Context

Reading the Overshoot Curve

Overshoot is a changing trajectory, not one date on which the climate system suddenly crosses a legal boundary; emissions and natural variability shape it over decades.

• The exceedance stage begins when long-term warming rises beyond 1.5°C; year-to-year natural variability can still produce individual calendar years above or below that level.
• The peak is the pathway’s highest warming level, shaped chiefly by how quickly and deeply carbon dioxide, methane and other greenhouse-gas emissions fall.
• The duration is time spent above 1.5°C; a longer stay expands cumulative exposure and raises the likelihood that ecosystems or communities reach hard adaptation limits.
• The decline requires sustained net-negative emissions after net-zero, while stabilization describes the later temperature level rather than restoration of every damaged natural and human system.
• Curve shape matters because a lower peak and shorter exceedance reduce severe impacts, adaptation costs, irreversible-loss risks and pressure on uncertain future removal capacity.

Three Linked Policy Tasks

Mitigation determines how high temperatures rise, adaptation manages unavoidable harm, and removals help create a later decline after net-zero is achieved.

• Rapid, sustained emissions reduction is the first lever: fossil-fuel transition, energy efficiency and methane cuts reduce both peak warming and the scale of future removal required.
• Adaptation must evolve with changing and compounding risks through heat action, resilient infrastructure, water security, early warning and social protection for exposed populations.
• Mitigation and adaptation reinforce each other: resilient energy, food, water and natural systems preserve society’s capacity to cut emissions as repeated climate shocks intensify.
• Reaching net-zero can halt further warming, but pushing temperatures downward requires net-negative emissions, meaning verified removals exceed the remaining emissions produced over time.
• Early adaptation cannot eliminate every loss; ice sheets, sea level, ecosystems, cultural heritage and livelihoods may respond slowly or irreversibly even after global temperature declines.

Carbon Removal Without Moral Hazard

CDR is a constrained residual tool whose credibility depends on deep emissions cuts, durable storage, fair burden-sharing and accountable long-term governance globally.

• Conventional CDR includes afforestation and soil management, but large land demand can compete with food, biodiversity and livelihoods, while drought or wildfire can reverse stored carbon.
• Novel methods such as direct air capture may offer more measurable storage, yet remain expensive, energy-intensive and unproven at the required global deployment scale.
• CDR should address residual emissions that are exceptionally difficult to eliminate, not preserve avoidable fossil-fuel use, inflate weak offsets or delay near-term mitigation.
• Governance must establish additionality, credible baselines, measurement, reporting, verification, storage permanence, liability and safeguards against ecological damage or unequal land burdens.
• Even a successful temperature decline cannot recreate the previous climate; delayed sea-level rise, displacement and ecosystem losses make loss and damage a continuing international justice issue.

Way Forward

Keep the Peak Low and the Exceedance Short

The pathway remains viable only if near-term action cuts warming and vulnerability before dependence on removals grows.

• Strengthen near-term national targets with credible sectoral delivery for power, transport, industry, buildings and methane, backed by transparent progress reviews.
• Integrate adaptation planning with observed and projected risk, including finance for vulnerable countries, locally led action and protection against non-linear hazards.
• Create robust CDR standards covering lifecycle emissions, land and water effects, storage duration, community consent, independent verification and responsibility for reversal.
• Preserve climate justice by requiring historically high emitters to move faster, finance resilience and avoid shifting removal or adaptation burdens onto vulnerable communities.

Conclusion

• Overshoot is risk management, not goal replacement: the Paris temperature aim remains, while immediate choices determine the peak, duration and feasibility of decline.
• A strong answer should connect deep emissions cuts, adaptive capacity, cautiously governed residual CDR and climate justice across the entire peak-and-decline pathway.

UPSC Practice Questions

Prelims MCQ 1

With reference to climate overshoot, consider the following statements:

1. It describes a pathway in which long-term warming exceeds a target before potentially declining below it.
2. One calendar year above 1.5°C by itself establishes that the Paris long-term threshold has permanently been breached.
3. Returning temperature downward after a peak requires net-negative emissions.

How many of the above statements are correct?

(a) Only one (b) Only two (c) All three (d) None

Answer: (b) Only two

Explanation:

Statements 1 and 3 are correct. Long-term warming is assessed over longer periods, so an individual annual anomaly is not the same as permanently crossing the long-term threshold.

Prelims MCQ 2

Which one of the following best describes the appropriate role of carbon dioxide removal in an overshoot pathway?

(a) Replacing immediate emissions reductions (b) Offsetting all present fossil-fuel emissions indefinitely (c) Complementing deep cuts by addressing residual emissions and enabling net-negative emissions (d) Guaranteeing reversal of all climate impacts

Answer: (c) Complementing deep cuts by addressing residual emissions and enabling net-negative emissions

Explanation:

UNEP treats CDR as necessary alongside sustained emissions cuts. Its role is constrained by scale, cost, permanence, land, energy and governance concerns.

UPSC Mains Questions

1. Climate overshoot is a pathway to be minimized and reversed, not a revision of the Paris Agreement’s temperature goal. Discuss.
2. Examine why carbon dioxide removal can support a temperature decline but cannot substitute for rapid and sustained emissions reduction.

Sources: UN Environment Programme, Limiting Overshoot report and The Hindu.

Frequently Asked Questions