World Climate and Climate Change Class 11 Geography Notes

This chapter explains the classification of world climates, major climatic regions and causes of climate change. It highlights Koeppen’s classification system, greenhouse gases, global warming and environmental impacts caused by climate change.

• Climate classification
• Koeppen’s climate classification
• Tropical climates
• Dry climates
• Warm temperate climates
• Cold climates
• Polar climates
• Climate change
• Global warming
• Greenhouse effect
• Greenhouse gases
• Kyoto Protocol

Approaches of Climate Classification

1. Empirical classification
2. Genetic classification
3. Applied classification

Empirical Classification

• Based on observed climatic data
• Uses temperature and precipitation

Genetic Classification

• Explains climate according to causes

Applied Classification

• Used for practical purposes

Meaning of Koeppen’s Classification

• Developed by V. Koeppen
• Based on temperature, rainfall and vegetation
• Empirical classification system

Features

• Uses capital and small letters
• Based on monthly and annual averages

Major Climatic Groups

Small Letters Used

Features of Tropical Climates

• Located between Tropic of Cancer and Tropic of Capricorn
• Hot and humid climate
• Heavy rainfall
• Low annual temperature range

Types of Tropical Climates

1. Af – Tropical Wet
2. Am – Tropical Monsoon
3. Aw – Tropical Wet and Dry

Tropical Wet Climate (Af)

• Found in Amazon Basin and Equatorial Africa
• Rainfall throughout the year
• Afternoon thunderstorms common
• Dense tropical evergreen forests

Tropical Monsoon Climate (Am)

• Found in Indian subcontinent
• Heavy summer rainfall
• Dry winter season

Tropical Wet and Dry Climate (Aw)

• Short wet season
• Long dry season
• High temperature throughout year
• Grasslands and deciduous forests

Characteristics

• Very low rainfall
• Rainfall insufficient for plant growth
• Frequent droughts
• Sparse vegetation

Distribution

• Found between 15°–60° latitudes

Types of Dry Climates

Highest Recorded Temperature

• Al Aziziyah, Libya
• 58°C recorded on 13 September 1922

Distribution

• Found between 30°–50° latitudes
• Located on eastern and western continental margins

Types

1. Cwa – Humid Subtropical
2. Cs – Mediterranean
3. Cfa – Humid Subtropical without dry season
4. Cfb – Marine West Coast

Mediterranean Climate (Cs)

• Hot dry summer
• Mild rainy winter
• Found around Mediterranean Sea and California
• Rainfall between 35–90 cm

Marine West Coast Climate (Cfb)

• Moderate climate
• Small annual temperature range
• Rainfall throughout year
• Found in Northwestern Europe and New Zealand

Distribution

• Found between 40°–70° north latitude
• Located in Europe, Asia and North America

Types

1. Df – Humid winter
2. Dw – Dry winter

Characteristics

• Cold snowy winters
• Short frost-free season
• Large annual temperature range

Types of Polar Climates

1. ET – Tundra
2. EF – Ice Cap

Tundra Climate (ET)

• Permafrost region
• Permanently frozen subsoil
• Short growing season
• Mosses and lichens dominate

Ice Cap Climate (EF)

• Found in Greenland and Antarctica
• Temperature below freezing even in summer
• Very little precipitation

Meaning of Climate Change

Climate change refers to long-term variation in climate and is a natural and continuous process.

Evidence of Climate Change

1. Glacial deposits
2. Tree rings
3. Historical records
4. Sediments

Climate Change in India

• Rajasthan had wet climate around 8,000 BC
• Harappan civilisation developed during wetter period

Important Climatic Events

• Sahel drought (1967–1977)
• Dust Bowl drought in USA during 1930s
• Little Ice Age (1550–1850)

Astronomical Causes

1. Sunspot activity
2. Milankovitch oscillations

Milankovitch Oscillations

• Changes in Earth’s orbit
• Axial tilt changes
• Earth wobbling
• Affect insolation

Volcanism

• Volcanic eruptions release aerosols
• Reduce incoming solar radiation

Anthropogenic Causes

• Increase in greenhouse gases
• Leads to global warming

Greenhouse Effect

The atmosphere allows shortwave solar radiation to enter but absorbs longwave terrestrial radiation, causing warming of the atmosphere.

Greenhouse Gases

1. Carbon dioxide (CO₂)
2. Methane (CH₄)
3. Nitrous oxide (N₂O)
4. Ozone (O₃)
5. Chlorofluorocarbons (CFCs)

Carbon Dioxide

• Main source – Fossil fuel combustion
• Main sinks – Forests and oceans

Ozone Hole

• Caused by CFC destruction of ozone layer
• Major depletion over Antarctica

Kyoto Protocol

• Declared in 1997
• Implemented in 2005
• Aim – Reduce greenhouse gas emissions

• Sea level rise
• Melting glaciers
• Ice cap melting
• Coastal flooding
• Environmental imbalance
• Increase in global temperature

Global Temperature Trend

• Temperature increased from 1885–1940
• 1990s were the warmest decade
• Global temperature increased about 0.6°C by end of 20th century
• 1998 recorded as warmest year

Very Short Answer Questions

1. Who developed Koeppen’s climate classification?
2. What is greenhouse effect?
3. What are greenhouse gases?
4. What is permafrost?
5. What is ozone hole?

Short Answer Questions

1. Explain Koeppen’s classification.
2. Explain tropical wet climate.
3. What are causes of climate change?
4. Explain greenhouse effect.
5. Discuss Mediterranean climate.

Long Answer Questions

1. Explain the major climatic groups under Koeppen’s classification.
2. Discuss causes and effects of global warming.
3. Explain greenhouse gases and their role in climate change.
4. Describe climate change in geological past.
5. Compare tropical and dry climates.

1. What is Koeppen’s climate classification?

It is an empirical climate classification based on temperature, rainfall and vegetation.

2. What is global warming?

Rise in Earth’s average temperature due to greenhouse gases.

3. Which gases are called greenhouse gases?

CO₂, CH₄, N₂O, O₃ and CFCs are major greenhouse gases.

4. What is the ozone hole?

Depletion of ozone concentration in stratosphere.

5. What is Mediterranean climate?

Climate with hot dry summers and mild rainy winters.

• Three Climate Classifications:
  • Empirical
  • Genetic
  • Applied
• Koeppen Classification:
  • Based on temperature and rainfall
• Major Climatic Groups:
  • A
  • B
  • C
  • D
  • E
• Tropical Climate:
  • Hot and humid
• Dry Climate:
  • Low rainfall
• Mediterranean Climate:
  • Hot dry summer
  • Mild rainy winter
• Polar Climate:
  • Extremely cold
• Climate Change:
  • Natural and continuous process
• Causes of Climate Change:
  • Sunspots
  • Orbital changes
  • Volcanism
  • Greenhouse gases
• Greenhouse Gases:
  • CO₂
  • CH₄
  • N₂O
  • O₃
  • CFCs
• Kyoto Protocol:
  • 1997
• Warmest Year:
  • 1998
• Global Warming Effects:
  • Sea level rise
  • Glacier melting
  • Coastal flooding