๐ Chapter 12: Climate & Climate Change of the World
๐ค️ 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).
๐ Classification of Climate
The Greeks were the first to classify climate.
There are three bases of climate classification:
- Empirical (เคเคจुเคญเคตिเค) – based on observation
- Genetic (เคเคจเคจिเค) – based on origin or causes
- Practical / Functional (Applied) – based on human use or activity
๐ 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.
๐ Koppen’s Climate Classification (1918)
- Empirical + Genetic method
- Based on temperature & precipitation
- Koppen noticed a strong link between vegetation & climate ๐ณ๐ฟ
Major Climate Groups by Koppen:
- Tropical Humid ๐ด
- Dry (B) ๐ต
- Warm Temperate (C) ☀️๐ฆ️
- Cold Snow Forest (D) ❄️๐ฒ
- Highland (E) ๐️
- Capital letters indicate main groups (A, C, D, E = humid; B = dry)
- Small letters denote seasonal characteristics
๐ Tropical Climate (Koppen)
Divided into three types:
- Af – Tropical Humid Climate ๐ด๐ง
- Rainfall all year round
- Dense evergreen forests
- Am – Tropical Monsoon Climate ๐ง️๐
- Heavy rain in summer due to monsoon winds
- Dry winters
- Found in Indian Subcontinent, NE South America, N Australia
- Aw – Tropical Humid Climate with Dry Winters ๐ฟ๐พ
- 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
๐ด Tropical Humid Climate
- Found near the equator ๐
- Major regions: Amazon Basin (South America), Western Equatorial Africa, Southeast Asian Islands
- Rainfall: Abundant all year with thunderstorms & afternoon showers ๐ง️
- Temperature: Uniformly high
- Max: 30°C
- Min: 20°C
- Annual temperature difference: Negligible
๐ฆ️ Tropical Monsoon Climate (Am)
- Found in: Indian Subcontinent, NE South America, Northern Australia
- Rainfall: Heavy in summer
- Winter: Dry season
๐️ Dry Climate
- Very low rainfall, insufficient for plant growth ๐ฑ
- Found between 15° to 60° latitudes north & south of equator
๐ต Desert Climate
- Located mainly between 15° to 60° latitudes
- Average temperature: 38°C
- Evaporation > Precipitation
- Sparse vegetation due to high temperature & low rainfall
๐พ China Equivalent Climate
- Found in eastern coastal areas (25°–45° latitudes)
- Average annual rainfall: 100 cm ๐ง️
- Rainfall: More in summer than winter
- Temperature:
- Hottest month: 27°C
- Winter: Mild, occasional frost ❄️
- Vegetation: Broad-leafed & mixed forests ๐ณ
❄️ 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 ๐จ️
๐️ 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 ❄️
๐ก️ 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
๐ฅ Global Warming
- Caused by increase in greenhouse gases ๐
- Effects:
- Melting of polar & mountain ice ❄️
- Rising sea levels → coastal flooding ๐ (Mumbai, Dhaka, Maldives)
- Saltwater intrusion in freshwater sources ๐ง
- Glacial melt → river floods ๐
⚡ Causes of Climate Change
- Astronomical Causes:
- Variation in solar energy due to sunspots
- Milankovitch cycles: Changes in Earth’s axial tilt affecting solar radiation
- Earthly Causes:
- Volcanic eruptions release aerosols → block sunlight → cool climate ๐
- Human Causes:
- Emission of CO₂, CH₄, CFCs → increase greenhouse effect
- Result: Global warming, extreme weather, climate shifts ๐ก️
✅ 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
