🌏 Class 11 Geography Chapter 12 – Climate & Climate Change of the World Notes in English

🌏 Class 11 Geography Chapter 12 – Climate & Climate Change of the World Notes in English

Atmospheric Studies
Published on By Amresh Academy

 

🌎 Chapter 12: Climate & Climate Change of the World

🌤️ What is Climate?

Climate influences our life, agriculture, trade, and industry. It sometimes even controls our daily activities.

  • Climate is the average weather over a long period (at least 30 years).

📊 Classification of Climate

The Greeks were the first to classify climate.
There are three bases of climate classification:

  1. Empirical (आनुभविक) – based on observation

  2. Genetic (जननिक) – based on origin or causes

  3. Practical / Functional (Applied) – based on human use or activity

🌍 Mediterranean Climate (Cs)

  • Found along the west coast of continents from 30° to 40° latitudes in the subtropical zone.

  • Characterized by hot dry summers and mild wet winters.

📌 Koppen’s Climate Classification (1918)

  • Empirical + Genetic method

  • Based on temperature & precipitation

  • Koppen noticed a strong link between vegetation & climate 🌳🌿

Major Climate Groups by Koppen:

  1. Tropical Humid 🌴

  2. Dry (B) 🌵

  3. Warm Temperate (C) ☀️🌦️

  4. Cold Snow Forest (D) ❄️🌲

  5. Highland (E) 🏔️

  • Capital letters indicate main groups (A, C, D, E = humid; B = dry)

  • Small letters denote seasonal characteristics

🌞 Tropical Climate (Koppen)

Divided into three types:

  1. Af – Tropical Humid Climate 🌴💧

    • Rainfall all year round

    • Dense evergreen forests

  2. Am – Tropical Monsoon Climate 🌧️🌞

    • Heavy rain in summer due to monsoon winds

    • Dry winters

    • Found in Indian Subcontinent, NE South America, N Australia

  3. Aw – Tropical Humid Climate with Dry Winters 🌿🌾

    • Long dry season, very little rain

    • Often leads to famine in dry season

    • Deciduous forests & grasslands

✅ Key Points to Remember

  • Climate is long-term average weather, not daily weather

  • Koppen’s classification is still widely used today

  • Climate affects vegetation, agriculture, and human life

🌴 Tropical Humid Climate

  • Found near the equator 🌞

  • Major regions: Amazon Basin (South America), Western Equatorial Africa, Southeast Asian Islands

  • Rainfall: Abundant all year with thunderstorms & afternoon showers 🌧️

  • Temperature: Uniformly high

    • Max: 30°C

    • Min: 20°C

  • Annual temperature difference: Negligible

🌦️ Tropical Monsoon Climate (Am)

  • Found in: Indian Subcontinent, NE South America, Northern Australia

  • Rainfall: Heavy in summer

  • Winter: Dry season

🏜️ Dry Climate

  • Very low rainfall, insufficient for plant growth 🌱

  • Found between 15° to 60° latitudes north & south of equator

🌵 Desert Climate

  • Located mainly between 15° to 60° latitudes

  • Average temperature: 38°C

  • Evaporation > Precipitation

  • Sparse vegetation due to high temperature & low rainfall

🌾 China Equivalent Climate

  • Found in eastern coastal areas (25°–45° latitudes)

  • Average annual rainfall: 100 cm 🌧️

  • Rainfall: More in summer than winter

  • Temperature:

    • Hottest month: 27°C

    • Winter: Mild, occasional frost ❄️

  • Vegetation: Broad-leafed & mixed forests 🌳

❄️ Taiga Climate

  • Found only in Northern Hemisphere (50°–70° N)

  • Regions: Alaska → Newfoundland, Scandinavia → Kamchatka Peninsula

  • Summers: Short & cold

  • Winters: Long & severe

  • Precipitation: Mostly in summer 🌨️

🏔️ Tundra Climate

  • Northern Hemisphere (60°–75° N)

  • Found in: Arctic coasts of N America & Eurasia, Greenland, Iceland

  • Summer: Mild, temperature < 10°C

  • Snow: Present all year ❄️

🌡️ Greenhouse Effect

  • Sun provides energy → absorbed by Earth’s surface → re-radiated as long-wave radiation

  • Atmosphere behaves like a greenhouse:

    • Short-wave radiation passes through

    • Long-wave radiation is absorbed, heating the atmosphere

  • Major greenhouse gases:

    • CO₂, CH₄, N₂O, O₃, NO, CFCs, CO

🔥 Global Warming

  • Caused by increase in greenhouse gases 🌎

  • Effects:

    • Melting of polar & mountain ice ❄️

    • Rising sea levels → coastal flooding 🌊 (Mumbai, Dhaka, Maldives)

    • Saltwater intrusion in freshwater sources 💧

    • Glacial melt → river floods 🌊

⚡ Causes of Climate Change

  1. Astronomical Causes:

    • Variation in solar energy due to sunspots

    • Milankovitch cycles: Changes in Earth’s axial tilt affecting solar radiation

  2. Earthly Causes:

    • Volcanic eruptions release aerosols → block sunlight → cool climate 🌋

  3. Human Causes:

    • Emission of CO₂, CH₄, CFCs → increase greenhouse effect

    • Result: Global warming, extreme weather, climate shifts 🌡️

✅ Key Points to Remember:

  • Climate affects life, economy, agriculture, forests

  • Koppen classification links climate with vegetation

  • Global warming is mostly human-induced but also influenced by natural factors
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