Last reviewed 16 Sept 2026 · Facts as of 16 Sept 2026 · 10 min read
Weather and climate
- Weather — short-term atmospheric conditions (hours to days) at a place.
- Climate — long-term average pattern of weather (commonly over 30 years) in a region.
- Climate change — significant, long-term change in climate patterns, attributed now largely to human activities increasing greenhouse gas concentrations (as well as natural variability).
Greenhouse effect
- Incoming short-wave solar radiation passes through the atmosphere and warms the earth; the earth emits long-wave infrared radiation, part of which is absorbed and re-emitted by greenhouse gases (GHGs) — keeping the earth warmer than it would otherwise be (natural greenhouse effect).
- Human emissions intensify this — the enhanced greenhouse effect → global warming.
Greenhouse gases
| Gas | Main anthropogenic sources | Notes |
|---|---|---|
| Carbon dioxide (CO₂) | Burning fossil fuels, cement production (calcination), deforestation | Largest contributor to warming; long-lived |
| Methane (CH₄) | Rice paddies, livestock (enteric fermentation), landfills, wastewater, fossil fuel leaks | Much stronger than CO₂ per molecule but shorter-lived |
| Nitrous oxide (N₂O) | Nitrogenous fertilisers, industrial processes | Long-lived, potent |
| Fluorinated gases (HFCs, PFCs, SF₆, NF₃) | Refrigeration and air conditioning, electrical switchgear (SF₆), industry | Very high GWP |
| Water vapour | Feedback (increases as air warms) | Not directly controlled |
| Ground-level ozone | Formed from pollutants | Short-lived climate forcer |
| Black carbon (aerosol) | Incomplete combustion | Short-lived climate forcer; darkens snow/ice |
Global warming potential (GWP)
- GWP — warming effect of a gas relative to CO₂ (GWP = 1) over a time horizon (commonly 100 years).
- CO₂-equivalent (CO₂e) .
- Methane's 100-year GWP is roughly 25–30 and N₂O roughly 265–300 (values differ between IPCC assessment reports); SF₆ has an extremely high GWP (thousands to tens of thousands).
Evidence of climate change
- Rising global average surface temperature — IPCC's Sixth Assessment Report (AR6) found global surface temperature over 2011–2020 to be about 1.1 °C above 1850–1900 levels, and recent years have been among the warmest on record.
- Increasing atmospheric CO₂ concentration (well above pre-industrial levels of about 280 ppm; now above 400 ppm).
- Retreat of glaciers and ice sheets, shrinking Arctic sea ice.
- Sea-level rise from thermal expansion and ice melt.
- More frequent/intense heatwaves, heavy rainfall events, droughts, and changes in cyclone behaviour.
- Ocean warming and acidification, coral bleaching.
- Shifts in species distributions and seasons.
IPCC
- Intergovernmental Panel on Climate Change (established 1988 by WMO and UNEP) assesses the science; Sixth Assessment Report (AR6) cycle concluded in 2023 — it stated it is unequivocal that human influence has warmed the atmosphere, ocean and land.
Impacts of climate change
| Sector | Impacts |
|---|---|
| Temperature and heat | Heatwaves, heat stress on workers (construction, agriculture), higher cooling demand |
| Water resources | Glacier retreat (Himalayan rivers), changing monsoon patterns, droughts, floods, groundwater stress |
| Agriculture and food | Yield variability, heat stress on crops, pests, changing sowing seasons |
| Coasts | Sea-level rise, coastal erosion, storm surges, salinisation (e.g. Sundarbans, low-lying cities) |
| Extreme events | Intense rainfall, urban flooding, cyclones, landslides, cloudbursts, glacial lake outburst floods (GLOFs) |
| Health | Vector-borne diseases (malaria, dengue), heat illness, water- and food-borne diseases |
| Ecosystems | Biodiversity loss, forest fires, coral reef damage |
| Infrastructure | Flooded roads, rail and airports; heat-related pavement damage and rail buckling; overtopping of drainage; damage to power and telecom networks; dam safety concerns; higher design loads (rainfall intensity, wind, temperature ranges) |
| Economy and society | Livelihood losses, migration, inequality — poorer communities most vulnerable |
India is highly vulnerable due to its long coastline, Himalayan glaciers, monsoon-dependent agriculture, dense population and exposure to heatwaves, floods, droughts and cyclones.
Mitigation and adaptation
| Mitigation — reducing emissions / enhancing sinks | Adaptation — reducing vulnerability to impacts |
|---|---|
| Renewable energy, energy efficiency | Climate-resilient infrastructure (higher plinths, improved drainage, elevated roads in flood-prone areas) |
| Electric mobility, public transport | Early warning systems (cyclones, floods, heatwaves) and heat action plans |
| Low-carbon cement (blended cements, calcined clays), green steel, material efficiency | Drought-resistant crops, efficient irrigation (micro-irrigation), watershed development |
| Afforestation, carbon sinks, reduced deforestation | Coastal protection — mangroves, sea walls, managed retreat |
| Methane reduction (landfill gas capture, better rice cultivation) | Water conservation — rainwater harvesting, recharge structures |
| Carbon capture, utilisation and storage (CCUS) | Insurance, disaster risk reduction, resilient housing |
Co-benefits: many actions (e.g. clean air, efficient buildings) deliver both mitigation and health/economic benefits.