Climate change: cause, impact and mitigation

Climate change is a long-term change in the average weather patterns – temperature, rainfall, wind and seasons – of a region or the whole Earth, lasting for decades or longer. The UNFCCC defines it as change attributed directly or indirectly to human activity that alters the composition of the global atmosphere, over and above natural variability.

Causes

Natural causes (minor in the present warming)

• Changes in solar output and in the Earth's orbit.
• Volcanic eruptions (dust and SO₂).
• Natural ocean–atmosphere cycles such as El Niño.

Human (anthropogenic) causes (main cause today)

1. Burning fossil fuels – coal, petrol, diesel and gas for power, transport and industry release CO₂.
2. Deforestation – fewer trees absorb CO₂, and burning forests releases it.
3. Agriculture – paddy fields and livestock release methane; chemical fertilisers release N₂O.
4. Industry – cement, steel, brick kilns; halocarbons from refrigeration.
5. Waste – landfills and open dumping give methane.
6. Urbanisation and population growth – more energy demand and land-use change.

These activities raise greenhouse gases: CO₂ is now over 420 ppm compared with about 280 ppm before 1750.

Impacts

In Nepal, temperature in the mountains is rising faster than the global average, glaciers are retreating and floods and landslides are increasing.

Mitigation measures

• Clean energy: expand hydropower, solar, wind and micro-hydro; phase down coal, oil and gas.
• Energy efficiency: LED lights, efficient motors, better building insulation, energy audits in industry.
• Clean transport: electric vehicles and electric public transport, cable cars, non-motorised transport (cycling, walking).
• Forests and land: stop deforestation, plant trees, community forestry, REDD+ (Reducing Emissions from Deforestation and Forest Degradation).
• Agriculture: less chemical fertiliser, organic farming, better manure handling, improved paddy water management.
• Waste: reduce, reuse, recycle; capture landfill methane; biogas from kitchen and animal waste.
• Industry: cleaner production, replacing old brick kilns with zig-zag kilns, low-carbon cement.
• Carbon pricing and policy: carbon tax, emissions trading, removing fossil fuel subsidies.
• Awareness and lifestyle: saving energy, less food waste, using public transport.

Adaptation measures are also needed, for example GLOF early-warning systems, drought-tolerant crops, water harvesting and climate-resilient infrastructure, as planned in Nepal's NAPA and National Adaptation Plan.