ACCELERATING CLIMATE RISKS AND 1.5C OVERSHOOT IMPACTS

Why In News?

The 1.5°C overshoot risk has taken center stage in global policy and scientific discussions due to the publication of the 10 New Insights in Climate Science 2026/2027 report, compiled jointly by Future Earth, The Earth League, and the World Climate Research Programme (WCRP).

What Does the 1.5°C Target Mean?

• Paris Agreement Goal: Article 2.1(a) of the 2015 Paris Agreement calls for keeping global warming well below 2°C above pre-industrial levels while pursuing efforts to limit it to 1.5°C.

• Temperature Benchmark: The 1.5°C limit refers to the long-term global average temperature, not a single unusually warm year.

• Pre-industrial Reference: Climate assessments generally use 1850–1900 as the baseline for measuring warming.

• Temporary Overshoot: An overshoot occurs when global temperature rises above 1.5°C for a period, potentially by around 0.1°C–0.35°C, before falling again through strong emissions cuts and Carbon Dioxide Removal (CDR).

What is Climate Overshoot?

Climate overshoot means when global average temperatures temporarily go past the 1.5°C safety limit set by the Paris Agreement before coming back down. 

Why It Happens

• Delayed Action: Greenhouse gas emissions remain too high, making a temporary temperature spike likely around mid-century.

• Two Key Factors: Scientists measure overshoot by its magnitude (how high temperatures rise above 1.5°C) and duration (how long they stay there).  

Major Risks and Impacts

• Irreversible Damage: Lowering temperatures later does not act like an "undo button". Ice sheets, sea-level rise, and species extinctions can become permanent.

• Tipping Points: Higher heat raises the danger of triggering dangerous thresholds, such as the collapse of major ocean currents or Amazon rainforest dieback.

• Human Toll: Communities face severe risks to food security, water access, health, and coastal living during the peak and decline phases.  

What Are The Impact Of Warming?

• Stronger Heatwaves: Every additional fraction of warming can increase the intensity of extreme heat, with tropical regions facing particularly high exposure.

• Water Stress: Higher temperatures can worsen drought, groundwater depletion and agricultural stress in vulnerable river basins, while also increasing the risk of intense rainfall.

• Long-Term Sea-Level Rise: Oceans absorb more than 90% of the excess heat in the climate system. Ocean warming and ice-sheet loss therefore continue to influence sea levels for centuries.

• Impact on Agriculture: Heat stress, changing rainfall patterns and soil degradation can reduce crop productivity and weaken natural carbon uptake.

• Ecosystem Loss: A 0.35°C overshoot could significantly damage coral ecosystems, while permafrost thaw can release large quantities of previously stored carbon.

• Human Health: Rising heat, water shortages and expanding climate-sensitive diseases can affect the health, income and productivity of billions of people.

What Do Recent Climate Indicators Show?

• Global Temperature: Global average surface temperature reached around 1.43°C above the pre-industrial level in 2025.

• CO₂ Emissions: Fossil fuels and cement production generated about 38.1 Gt of CO₂ in 2025, marking a new record.

• Atmospheric CO₂: Atmospheric carbon dioxide reached around 425.6 ppm in 2025, approximately 53% above pre-industrial levels.

• Weak Emission Commitments: Existing national climate pledges imply only about a 12% reduction in global emissions by 2035 from 2019 levels, compared with the much deeper cuts needed for a 1.5°C pathway.

• Record-Warm Period: The 2015–2025 period included the 11 warmest years in the instrumental record, according to the WMO.

• 2035 Emission Gap: Avoiding a large overshoot would require global greenhouse gas emissions to fall by roughly half by 2035, implying rapid annual reductions.

Impacts Of Global Warming 

Economic Damage

• GDP Impact: Some recent time-series research estimates that a 1°C rise in global temperature could reduce global GDP by around 12% at peak, substantially above estimates from older approaches.

• Social Cost of Carbon: Models that include global temperature shocks and capital depreciation estimate the Social Cost of Carbon (SCC) at around $1,056 per tonne of CO₂.

• Long-Term Welfare Loss: Under a high-warming pathway reaching around 3°C, permanent welfare losses could become very large, with estimates reaching 31% in present value and 52% by 2100.

• Lost Economic Output: Estimates suggest that without global warming between 1960 and 2019, global GDP per capita could have been substantially higher.

Impact On Developing Countries 

• Climate-Sensitive Livelihoods: Many developing economies depend heavily on agriculture, livestock and fisheries, which remain highly sensitive to temperature and rainfall changes.

• Limited Fiscal Capacity: High borrowing costs and restricted public finances make it difficult to invest in large-scale climate-resilient infrastructure.

• Infrastructure Deficits: Weak transport, sanitation, healthcare and other basic infrastructure can magnify the effects of climate disasters.

• Higher Heat Exposure: Tropical developing regions face greater exposure to extreme heat and could experience much larger economic losses than wealthier economies under high-overshoot pathways.

• Development Setbacks: Climate disasters can force governments to redirect scarce resources from healthcare, education and development towards emergency response and reconstruction.

What Should Countries Do Next?

• Raise 2035 Targets: Countries need stronger Nationally Determined Contributions (NDCs) that bring global emissions closer to a 1.5°C-compatible pathway.

• Expand Renewable Energy: Governments should rapidly scale up solar, wind, transmission networks and energy storage across power, transport and industry.

• Cut Fossil-Fuel Dependence: Phasing down inefficient fossil-fuel subsidies and redirecting investment towards clean energy and natural carbon sinks can reduce future emissions.

• Scale Up Climate Finance: International public and private finance needs to increase substantially, including efforts towards the $1.3 trillion annual climate-finance goal by 2035.

• Plan for Adaptation: Countries should prepare long-term adaptation strategies that account for climate risks throughout the century, including possible temporary warming above 1.5°C.

• Prioritise Vulnerable Populations: Climate finance and resilience measures should focus strongly on low-income and highly exposed tropical communities.

Conclusion

Breaching 1.5°C causes lasting extreme weather, ecosystem loss, and economic damage. Mitigating these risks requires swift emission cuts, adaptation, and enhanced climate finance.

Source: DOWNTOEARTH