SYLLABUS:

GS-3- Conservation, environmental pollution and degradation, environmental impact assessment.

Context: According to the 22nd edition of the WMO Greenhouse Gas Bulletin, atmospheric concentrations of major greenhouse gases reached unprecedented levels in 2025, increasing the risk of long-term global warming and extreme climate events.

Key Findings of the Report

• Record Concentrations of Major Greenhouse Gases: Globally averaged atmospheric concentrations of the three major long-lived greenhouse gases reached unprecedented levels in 2025.

• CO₂ accounts for approximately 66% of radiative forcing from long-lived greenhouse gases, followed by methane (16%) and nitrous oxide (6%).
• The past 11 years have been the warmest on record.

• Rising Carbon Dioxide Concentrations: Atmospheric CO₂ increased from 377.5 ppm in 2004 to 426.8 ppm in 2025.

• Its annual growth rate has tripled, from around 0.8 ppm in the 1960s to 2.4 ppm during 2011–2020.
• CO₂ increased by 2.8 ppm between 2024 and 2025, lower than the record rise of 3.6 ppm in 2023–2024, but slightly above the 10-year average of 2.63 ppm.
• During 2015–2024, approximately 50% of human-caused CO₂ emissions accumulated in the atmosphere, while oceans absorbed 29% and land absorbed 21%.
• The NOAA Annual Greenhouse Gas Index shows that radiative forcing from long-lived greenhouse gases increased by 56% between 1990 and 2025, with CO₂ accounting for around 81% of this increase.
• The slower CO₂ growth in 2025 was partly linked to the recovery of land carbon sinks and reduced fire emissions. However, continued fossil fuel use is expected to increase concentrations further.

• Methane and Nitrous Oxide: Around 65% of methane emissions are anthropogenic, mainly from livestock, rice cultivation, fossil fuel exploitation, landfills and biomass burning. 

• The remaining 35% comes from natural sources, including wetlands and termites.
• Methane increased by 6 ppb in 2025, lower than the 8 ppb rise in 2024 and the 10-year average annual increase of 10.2 ppb.
• Around 35% of nitrous oxide emissions are anthropogenic, mainly from agricultural fertilisers and industrial activities. Human-induced emissions increased by 30% over four decades, reaching 7.3 teragrams of nitrogen per year.

• Emerging Concerns:  

• Sulphur hexafluoride (SF₆) is used mainly as an electrical insulator in high-voltage equipment. Its atmospheric concentration increased by 249% between 1995 and 2025, reaching 12.24 ppt. 

                   It has a global warming potential around 24,300 times that of CO₂ over 100 years and can remain in the atmosphere for up to 3,200 years.

• Hydrogen (H₂) is not directly a greenhouse gas but can indirectly contribute to warming by affecting atmospheric chemistry and extending methane's lifetime. 

                   Its atmospheric concentration increased from 532 ppb in 2010 to 560 ppb in 2024. The WMO has highlighted the need to minimise hydrogen leakage.

Recommendations and Way Forward

• Strengthen atmospheric monitoring: Improve global greenhouse gas observations through the WMO's Global Atmosphere Watch programme.

• Reduce CO₂ emissions: Accelerate the transition away from fossil fuels and strengthen natural carbon sinks.

• Control methane and nitrous oxide: Reduce emissions from agriculture, livestock, waste management and fertiliser use.

• Limit SF₆ emissions: Promote alternatives with lower global warming potential in electrical equipment.

• Minimise hydrogen leakage: Strengthen leak prevention across hydrogen production, pipelines, storage facilities and fuel cells.