Context
UNEP report released a report, Limiting Overshoot – Navigating Exceedance of 1.5°C and Pathways Towards Return which sets out an “overshoot, peak and decline” pathway.
Need of “overshoot, peak and decline” pathway:
- Paris Agreement: The 2015 Agreement aims to keep the rise in global average temperature well below 2°C while pursuing efforts to limit it to 5°C above pre-industrial levels.
- Scientific significance: The 1.5°C threshold is important because risks from extreme heat, coral-reef loss, ice-sheet instability and food-system disruption increase sharply with further warming.
- Changing reality: The world is currently heading towards around 6°C warming by 2100, with a projected range of 1.9°C–3.6°C.
- Climate commitments: Even if countries fully implement their existing national climate plans and net-zero targets, peak warming could reach around 1.8°C.
- Carbon budget: The amount of CO₂ that can still be emitted while maintaining a temperature target is limited.
- Rapid depletion: Continued fossil-fuel emissions consume this remaining carbon budget and increase the likelihood of a larger overshoot.
| Keyword | Meaning | Climate Action Required |
| Overshoot | Global temperature temporarily exceeds 1.5°C above the pre-industrial level. | Prevent the overshoot from becoming large or prolonged. |
| Peak | The highest level of warming reached before temperatures begin to fall. | Rapidly cut CO₂ and methane emissions to keep peak warming as low as possible. |
| Decline | Global temperature starts falling after the peak as atmospheric CO₂ is reduced. | Achieve net-negative emissions, mainly through deep emission cuts and carbon removal. |
Key Policy Shift Under the UNEP Overshoot Approach
- From prevention to management: Shift from only preventing the 1.5°C breach to minimising the magnitude and duration of overshoot.
- From mitigation alone to multiple actions: Combine emission cuts, adaptation and carbon removal.
- From long-term to immediate action: Prioritise rapid near-term emission reductions, especially methane.
- From avoiding damage to limiting damage: Prepare for unavoidable climate impacts while continuing mitigation.
- From supplementary to essential CDR: Make carbon dioxide removal an important tool for returning below 1.5°C.
- From delayed action to early action: Recognise that every delay increases future warming and carbon-removal requirements.
Consequences of rising fractions of temperature:
- Sea-level rise: Higher warming accelerates glacier and ice-sheet melting, increasing long-term sea-level rise.
- Coral reefs: Continued Ocean warming increases coral bleaching and reef degradation, threatening marine ecosystems.
- Glaciers: UNEP projects that more than one-quarter of global glacier mass could be lost by 2100, creating major implications for mountain water resources.
- Food security: Without effective adaptation, global food production could decline by up to 14% by 2050 under increasing climate stress.
- Extreme events: Higher warming increases the frequency and intensity of heatwaves, floods, droughts and wildfires.
- Tipping points: Prolonged warming increases the probability of crossing irreversible thresholds in major Earth systems.
What are tipping points?
A tipping point is a critical threshold in the climate system beyond which a small additional change can trigger large, rapid and potentially irreversible changes.
| Tipping Points | Key Risk / Consequence |
| 1. Greenland Ice Sheet | Accelerated melting → long-term sea-level rise |
| 2. West Antarctic Ice Sheet | Ice-sheet collapse → major sea-level rise |
| 3. AMOC (Atlantic Meridional Oceanic circulation) | Weakening of ocean circulation → changes in rainfall, temperatures and regional climate |
| 4. Amazon Rainforest | Forest dieback → loss of carbon sink and biodiversity |
| 5. Arctic Sea Ice | Large-scale ice loss → lower albedo and greater warming |
| 6. Permafrost | Thawing releases CO₂ and methane, creating further warming |
| 7. Coral Reef Systems | Persistent ocean warming → widespread coral loss and ecosystem collapse |
| 8. Boreal Forests | Warming, drought and wildfires → forest dieback and carbon release |
| 9. West African Monsoon / Sahel | Abrupt rainfall changes → drought, flooding and livelihood disruption |
Methane Offers a Window to Lower Peak Warming
- High warming potential: Methane is a highly potent greenhouse gas and contributes around 5°C of observed warming.
- Short atmospheric lifetime: Unlike CO₂, methane remains in the atmosphere for a relatively shorter period.
- Rapid climate benefit: Cutting methane can therefore produce faster near-term reductions in warming.
- Major sources: Important sources include livestock, fossil-fuel production, landfills and wastewater.
- Complementary role: CO₂ reduction remains essential for long-term temperature stabilisation, while methane reduction can help lower the peak during an overshoot pathway.
India at the Receiving End of Climate Overshoot
- Himalayan risks: Rising temperatures can accelerate glacier retreat, cryosphere changes and glacial hazards.
- Agriculture: Increasing heat stress and changing rainfall patterns can affect crop productivity and food security.
- Water security: Changes in glaciers, precipitation and evaporation can increase pressure on India’s water resources.
- Coastal vulnerability: Sea-level rise threatens coastal cities, infrastructure and livelihoods.
- Carbon sinks: Forests, wetlands and ecosystem restoration can strengthen carbon sequestration while providing ecological co-benefits.
Way Forward
- Accelerate decarbonisation: Rapidly reduce dependence on coal, oil and gas through clean energy and efficiency.
- Target methane: Cut methane emissions from livestock, fossil fuels and waste for quick near-term gains.
- Build climate resilience: Strengthen early-warning systems, climate-resilient infrastructure and disaster preparedness.
- Protect natural sinks: Restore forests, wetlands, mangroves and other carbon-rich ecosystems.
- Mobilise climate finance: Ensure developing countries have access to finance, technology and capacity-building.
- Strengthen global cooperation: Improve implementation of NDCs and net-zero commitments and coordinate action to limit overshoot.
- Ensure climate justice: Make the transition affordable, inclusive and sensitive to the needs of vulnerable populations.
FAQs
Q1. What is the central message of UNEP’s overshoot report?
Ans: The report argues that a temporary overshoot of 1.5°C is increasingly likely, making it essential to minimise the peak and duration of warming and eventually bring temperatures down.
Q2. What does an “overshoot pathway” mean?
Ans: It refers to a pathway in which warming temporarily exceeds 1.5°C before declining through deep emission reductions and net-negative emissions.
Q3. What warming does the current-policy pathway indicate for 2100?
Ans: Around 2.6°C, with a projected range of 1.9°C–3.6°C.
Q4. Why is methane important in limiting climate overshoot?
Ans: Its short atmospheric lifetime means that rapid methane reductions can lower near-term warming and help reduce peak temperatures.
Q5. Why is carbon removal necessary after overshoot?
Ans: Returning below 1.5°C requires net-negative emissions, meaning more CO₂ must be removed from the atmosphere than is being emitted.
Q6. Why is delaying emission reduction particularly costly?
Ans: Continued emissions raise peak warming, while reversing that warming later requires very large-scale carbon removal.
