Recent Developments:
- The United Nations Environment Programme (UNEP) released its Limiting Overshoot: Navigating exceedance of 1.5°C and pathways towards return report on 2 September 2026, warning that crossing the 1.5°C warming threshold is now widely assessed as unavoidable under current and near-term trajectories.
- The report proposes an “overshoot, peak and decline” pathway, under which global temperatures temporarily exceed 1.5°C, peak at the lowest possible level and subsequently decline towards the Paris Agreement goal.
- Even if countries fully implement their existing climate commitments and net-zero targets, UNEP projects peak warming of around 1.8°C, while current policies point towards approximately 2.6°C warming by 2100.
- UNEP therefore argues that climate policy must simultaneously pursue rapid emission reductions, adaptation and carbon removal, rather than treating the possibility of exceeding 1.5°C as a reason for policy resignation.
Background of the 1.5°C Goal:
Paris Agreement and Temperature Target:
- The Paris Agreement, adopted at COP21 in 2015, seeks to hold the increase in global average temperature to well below 2°C above pre-industrial levels while pursuing efforts to limit warming to 1.5°C.
- The 1.5°C threshold is important because climate risks generally increase with every additional fraction of warming, particularly for extreme heat, sea-level rise, ecosystems, food security and vulnerable communities.
- The threshold should not be interpreted as a single physical “tipping point” at which climate change suddenly becomes catastrophic; rather, it represents a risk-management benchmark within international climate policy.
- The IPCC has established that overshooting a warming level produces greater and potentially irreversible impacts compared with pathways that remain below that level.
Why the Overshoot Concept Matters:
- Overshoot refers to a temporary period during which global warming exceeds a specified temperature level before subsequently declining through sustained net-negative CO₂ emissions.
- The larger and longer the overshoot, the greater the associated risks and the larger the quantity of carbon dioxide removal (CDR) required to reverse warming.
- The new UNEP approach therefore shifts the policy question from simply “Can 1.5°C be avoided?” towards “How low can peak warming be kept, and how quickly can temperatures return below 1.5°C?”
UNEP’s Overshoot, Peak and Decline Pathway:
Three-Stage Climate Strategy:
- Overshoot: Global temperatures temporarily rise above 1.5°C because cumulative greenhouse-gas emissions have already consumed much of the remaining carbon budget.
- Peak: Governments seek to minimise the maximum temperature reached through accelerated reductions in CO₂ and short-lived climate pollutants, particularly methane.
- Decline: Temperatures are gradually reduced through sustained net-negative CO₂ emissions, requiring atmospheric carbon removal to exceed remaining emissions.
Projected Warming Scenarios:
- UNEP estimates that full implementation of existing climate commitments could still result in approximately 1.8°C peak warming, demonstrating the gap between present commitments and the 1.5°C objective.
- Under current policies, warming could reach approximately 2.6°C by 2100, highlighting the continuing implementation and ambition gap in global climate action.
- The IPCC similarly finds that pathways returning to 1.5°C after an overshoot require substantially greater net-negative CO₂ emissions than pathways that avoid or minimise overshoot.
Compounding Costs of Overshoot:
Environmental and Socioeconomic Risks:
- Higher peak warming increases the likelihood of extreme heat, heavy precipitation, wildfires, glacier loss, sea-level rise and ecosystem degradation.
- Coral reefs, glaciers, polar ecosystems and coastal systems are particularly vulnerable because some impacts become irreversible or continue for very long periods even after temperatures decline.
- Overshoot can increase the risk of crossing climate tipping points, including instability of the Greenland and West Antarctic ice sheets, Atlantic Meridional Overturning Circulation and Amazon ecosystems.
- Temperature reversal does not automatically reverse every climate impact; for example, sea-level rise can continue for decades to millennia even after global warming begins to decline.
- The resulting burden is likely to fall disproportionately on developing countries and vulnerable populations, raising issues of climate justice, adaptation finance and loss and damage.
Why Delay Becomes More Costly:
Carbon Budget and Negative Emissions:
- The remaining carbon budget represents the cumulative amount of CO₂ that can still be emitted while retaining a specified probability of limiting warming to a particular temperature level.
- Continued high emissions reduce this budget and increase the probability of overshoot, thereby transferring a larger mitigation burden to future generations.
- The IPCC estimates that reducing global temperature by 0.1°C through atmospheric carbon removal requires roughly 220 GtCO₂ of net-negative emissions, with a likely range of 160–370 GtCO₂.
- Consequently, delayed emission reductions create a double burden because they increase both peak warming and the subsequent requirement for carbon removal.
Methane as a Near-Term Priority:
Short-Lived Climate Pollutant:
- Methane (CH₄) is a potent greenhouse gas with a much shorter atmospheric lifetime than CO₂, making methane mitigation particularly important for reducing near-term warming.
- The IPCC finds that rapid reductions in methane and other non-CO₂ emissions can lower peak warming and reduce dependence on later net-negative CO₂ emissions and CDR.
- Key methane-reduction opportunities exist in oil and gas operations, coal mining, livestock, rice cultivation, landfills and wastewater management.
- For an overshoot strategy, methane reduction has strategic importance because it can deliver relatively rapid climate benefits while CO₂ reduction remains essential for long-term temperature stabilisation.
Role of Carbon Dioxide Removal:
Need and Limitations:
- Returning global warming below 1.5°C after an overshoot requires carbon dioxide removal, because atmospheric CO₂ concentrations must decline sufficiently to produce net-negative emissions.
- CDR options include afforestation, reforestation, ecosystem restoration, soil-carbon sequestration, bioenergy with carbon capture and storage and direct air capture.
- Large-scale CDR can create trade-offs involving land, water, food security, biodiversity, energy and local livelihoods, particularly when land-intensive methods are expanded rapidly.
- CDR should therefore complement rather than substitute deep emission reductions, because excessive dependence on future removals could increase technological, ecological and governance risks.
Implications for India:
Climate Policy and Development:
- India faces a dual challenge of pursuing rapid economic development and poverty reduction while limiting growth in greenhouse-gas emissions.
- Greater emphasis on renewable energy, energy efficiency, electric mobility, green hydrogen, public transport and resilient infrastructure can reduce emissions while supporting long-term development.
- India also requires stronger heat-action plans, climate-resilient agriculture, water management, urban cooling, disaster preparedness and early-warning systems because adaptation needs will rise even under successful mitigation.
- Methane reduction can provide opportunities through improved waste management, livestock practices, landfill-gas capture and agricultural interventions.
- India can also contribute to nature-based carbon removal through ecosystem restoration, afforestation and improved land management, while ensuring that carbon projects do not undermine food security or community rights.
Challenges in Global Climate Governance:
Equity and Climate Justice:
- A major challenge is determining who should bear the costs of emission reductions, adaptation and carbon removal.
- Developing countries argue that historical emissions and differences in financial and technological capacity must remain central to climate negotiations.
- Large-scale CDR may generate new disputes over land acquisition, carbon accounting, permanence, monitoring and benefit sharing.
- Climate finance therefore remains essential for enabling developing countries to pursue both mitigation and adaptation without compromising developmental priorities.
Need for Integrated Action:
- The Paris Agreement also seeks to strengthen countries’ ability to adapt to climate impacts and build resilience, making mitigation and adaptation complementary rather than competing priorities.
- The first Global Stocktake, concluded at COP28 in 2023, established an important mechanism for assessing collective progress and informing stronger national climate action.
- The central policy objective should therefore remain deep and immediate emission reductions, while preparing for unavoidable impacts and developing responsible carbon-removal capacity.
Value Addition for UPSC:
Keywords and Answer Enrichment:
- Overshoot: Temporary exceedance of a specified warming level followed by a decline in global temperature.
- Peak Warming: The maximum level of warming reached before temperatures begin to decline.
- Net-Negative Emissions: A situation in which global removal of greenhouse gases exceeds global emissions.
- Carbon Dioxide Removal: Human activities that remove CO₂ from the atmosphere and store it durably.
- Tipping Points: Critical thresholds beyond which changes in climate systems can become self-reinforcing and difficult or impossible to reverse.
- Climate Justice: The principle that climate responsibilities and burdens should reflect historical emissions, capabilities and differing vulnerabilities.
- UPSC-ready conclusion: The prospect of 1.5°C overshoot should not become a justification for climate inaction; it strengthens the case for faster mitigation, aggressive methane reduction, climate-resilient development, equitable finance and carefully governed carbon removal.
