Short note: Climate change

Climate change is the long-term change in the Earth's average climate – temperature, rainfall, wind and frequency of extreme events – observed over decades or longer. The current rapid change is mainly caused by human activities that add greenhouse gases to the atmosphere. Global temperature has already risen about 1.1 °C above pre-industrial levels (IPCC).

Greenhouse gases and causes

• CO₂ – burning coal, oil and gas; deforestation; cement.
• CH₄ (methane) – livestock, rice paddies, landfills.
• N₂O – chemical fertilisers.
• CFCs/HFCs – refrigerants, aerosols.
• Water vapour and black carbon also add to warming.

These gases let sunlight in but trap outgoing heat – the enhanced greenhouse effect.

Impacts

• Global warming, heat waves, melting glaciers and sea-level rise.
• Irregular monsoon, floods, landslides and droughts.
• Lower crop yields, food and water insecurity.
• Spread of vector-borne diseases (dengue, malaria) to higher areas.
• Biodiversity loss.
• In Nepal: temperature is rising faster than the global average in the mountains; glacial lakes are growing (GLOF risk); springs are drying; Nepal is among the most vulnerable countries although it contributes a tiny share (well under 0.1%) of global emissions.

Responses

• Mitigation – cut emissions: renewable energy, energy efficiency, electric transport, forest protection (REDD+).
• Adaptation – adjust to impacts: drought-resistant crops, early warning systems, LAPA/NAP in Nepal.
• International efforts – UNFCCC (1992), Kyoto Protocol (1997), Paris Agreement (2015) to keep warming well below 2 °C and pursue 1.5 °C.