World Climate and Climate Change

Climate is what we expect; weather is what we get. — Mark Twain

11.1 Köppen Climate Classification

Wladimir Köppen classified climates based on temperature, precipitation, and vegetation:

India spans tropical (Am, Aw), arid (BWh, BSh), and highland (H) types.

11.2 Major World Climates

• Equatorial — year-round rain, rainforests (Amazon, Congo)
• Tropical monsoon — seasonal rain reversal (Indian subcontinent)
• Mediterranean — dry summers, wet winters
• Desert — extreme aridity (Sahara, Arabian)
• Tundra — short summers, permafrost (Arctic)

Continentality and maritime influence shape temperature extremes.

11.3 Climate Change

Global warming — rise in average surface temperature due to increased greenhouse gases (CO₂, CH₄, N₂O).

Evidence:

• Rising sea levels (thermal expansion + ice melt)
• Melting glaciers and Arctic ice
• More frequent extreme weather events
• Shifting seasons and species ranges

The IPCC reports attribute recent warming primarily to human activities since the Industrial Revolution.

11.4 India and Climate Change

Impacts on India:

• Glacial retreat in Himalayas threatens water security (Ganga, Indus headwaters)
• Coastal flooding — Mumbai, Chennai, Sundarbans at risk
• Agriculture — altered monsoon timing affects kharif and rabi crops
• Heatwaves — increasing frequency and intensity

Mitigation: renewable energy, afforestation, emission targets. India committed to net zero by 2070 at COP26.

Chapter Summary

• Köppen classification groups climates by temperature and precipitation
• World climates range from equatorial to polar
• Anthropogenic greenhouse gas emissions drive global warming
• India faces glacial melt, sea-level rise, and monsoon disruption
• International cooperation (Paris Agreement) essential for mitigation

Exercises (NCERT)

• Exercise 1 — Köppen climate types and their characteristics
• Exercise 2 — evidence and causes of climate change
• Exercise 3 — impacts of climate change on India; mitigation strategies