NCERT Class 11 Physical Geography Chapter 12 – World Climate and Climate Change

NCERT Class 11 Physical Geography Chapter 12 explains different climate types found across the world and the causes of climate change. Students should refer to the official NCERT website at for authentic textbooks and syllabus updates. In NCERT Class 11 Physical Geography Chapter 12, students study major climatic regions like equatorial, tropical, temperate and polar climates along with factors affecting global climate patterns.

NCERT Class 11 Physical Geography Chapter 12 is extremely important for CBSE board exams and competitive exams like UPSC and BPSC because climate classification and climate change are frequently asked topics. A strong understanding of NCERT Class 11 Physical Geography Chapter 12 helps in answering questions related to global warming, environmental issues and agriculture geography.

For structured preparation of NCERT Class 9–12 for UPSC, BPSC and State PCS examinations, strengthen your basics with our complete NCERT Book Notes PDF for Class 9-12, available inside the NCERT foundation course level-2.

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1. Koeppen’s scheme of classification of climate

• Wladimir Köppen classified world climates based on the relationship between temperature and precipitation and their impact on natural vegetation.
• His scheme is empirical and identifies climate types using capital and small letters to denote temperature and rainfall characteristics.
• The first letter represents the major climate group, the second letter indicates seasonal precipitation, and the third letter shows temperature characteristics.
• Köppen divided world climates into five major groups: A (Tropical Humid), B (Dry), C (Warm Temperate), D (Cold Snow Forest), and E (Polar); later H (Highland) was added.
• The classification closely corresponds with the distribution of natural vegetation, making it practical and widely used.
• The boundaries between climatic regions are determined using specific temperature and precipitation limits.

1.1 Group A : Tropical Humid Climates

• Group A climates are found between the Tropics of Cancer and Capricorn, where the mean monthly temperature remains above 18°C throughout the year.
• These climates are characterized by high temperature and significant rainfall, though the seasonal distribution of rainfall varies.
• This group is divided into three types: Af (Tropical Rainforest Climate), Am (Tropical Monsoon Climate) and Aw (Tropical Wet and Dry or Savanna Climate).
• Af Climate has rainfall throughout the year with no dry season, and is typically found in the Equatorial regions.
• Am Climate has heavy rainfall concentrated in a short wet season, associated with monsoon winds.
• Aw Climate has a distinct dry season in winter and wet summer, common in regions away from the equator.

1.2 Dry Climates : B

• Group B climates are characterized by deficiency of precipitation, where evaporation exceeds precipitation, making them arid or semi-arid.
• These climates are divided into BW (Desert Climate) and BS (Steppe Climate) based on the degree of dryness.
• BW (Desert Climate) has extremely low rainfall and sparse vegetation; it is further classified into BWh (Hot Desert) and BWk (Cold Desert) based on temperature.
• BS (Steppe Climate) receives slightly more rainfall than deserts and supports short grasses; it is subdivided into BSh (Hot Steppe) and BSk (Cold Steppe).
• Dry climates are mainly located around 30° North and South latitudes, in the interiors of continents and in regions influenced by cold ocean currents.

1.3 Warm Temperate (Mid-Latitude) Climates – C

• Group C climates are found in the mid-latitudes, mainly between 30° and 60° latitudes, where the coldest month’s mean temperature ranges between –3°C and 18°C, and at least one month records temperature above 10°C.
• These climates are influenced by westerlies and show moderate temperature with distinct seasonal variations.
• Group C is subdivided into Cs (Mediterranean Climate), Cw (Humid Subtropical with Dry Winter) and Cf (Humid Subtropical without Dry Season).
• Cs Climate has dry summers and wet winters, typically found in regions around the Mediterranean Sea and similar west-coast locations.
• Cw Climate experiences dry winters and wet summers, often influenced by monsoon circulation, and is common in parts of South and East Asia.
• Cf Climate has rainfall throughout the year without a distinct dry season, commonly located on the eastern margins of continents.

1.4 Cold Snow Forest Climates (D)

• Group D climates are found in the interior and eastern parts of continents in the Northern Hemisphere, mainly between 40° and 70° latitudes.
• These climates have a mean temperature below –3°C in the coldest month and above 10°C in the warmest month, showing strong seasonal contrast.
• Winters are long and severe, while summers are short but relatively warm.
• This group is subdivided into Df (no dry season) and Dw (dry winter) types.
• These regions support coniferous forests (taiga) and are commonly referred to as Boreal Forest Climate.

1.5 Polar Climates (E)

• Group E climates are found in the high latitudes, mainly beyond 70° North and South, where temperatures remain extremely low throughout the year.
• In these climates, the mean temperature of the warmest month does not exceed 10°C, preventing the growth of trees.
• This group is divided into ET (Tundra Climate) and EF (Ice Cap Climate).
• ET (Tundra Climate) has short cool summers with temperatures slightly above freezing, allowing the growth of mosses and lichens.
• EF (Ice Cap Climate) remains below freezing throughout the year, with permanent ice cover, as seen in Antarctica and Greenland.

1.6 Highland Climates (H)

• Highland Climates (H) are found in mountainous regions where climate varies with altitude rather than latitude.
• Temperature decreases with height according to the lapse rate, leading to vertical climatic zones.
• These climates show sharp contrasts over short distances due to differences in slope, aspect and elevation.
• Highlands experience variations in precipitation, with heavy rainfall on the windward slopes and drier conditions on the leeward slopes.
• Vegetation and climatic conditions change rapidly with altitude, forming distinct altitudinal belts.

2. Climate change

• Climate change refers to long-term changes in temperature, precipitation and other climatic elements over a large area and extended period.
• The Earth’s climate has not remained constant and has undergone alternating warm and cold periods in the past.
• Historical records such as crop yields, floods and human migration provide evidence of climatic variations.
• Significant climatic episodes include warm and dry conditions during the 10th and 11th centuries, and the “Little Ice Age” (1550–1850) in Europe.
• From about 1885 to 1940, global temperatures showed an upward trend, while after 1940, the rate of increase slowed.

2.1 Climate in the Recent Past

• Historical evidence such as crop failures, floods and migration of people indicate that climate has changed several times in recorded history.
• Europe experienced warm and dry conditions during the 10th and 11th centuries, which enabled the Vikings to settle in Greenland.
• A prolonged cold phase known as the “Little Ice Age” (1550–1850) affected Europe with cooler conditions.
• Between 1885 and 1940, global temperatures showed a noticeable upward trend.
• After 1940, the increase in temperature slowed down for some decades before recent warming trends.

2.2 Causes of Climate Change

• The causes of climate change are grouped into astronomical causes and terrestrial causes.
• Astronomical causes include changes in solar output related to sunspot activity, where an increase in sunspots is associated with cooler and wetter conditions, though the relationship is not statistically strong.
• Another astronomical explanation is the Milankovitch oscillations, involving variations in the Earth’s orbital characteristics, axial tilt and wobbling, which alter the amount of insolation received.
• Volcanic eruptions release large amounts of aerosols into the atmosphere, reducing incoming solar radiation and temporarily lowering global temperatures, as observed after the Pinatubo and El Cion eruptions.
• The most significant recent cause is the increasing concentration of greenhouse gases due to human activities, which contributes to global warming.

3. Global Warming

• Global Warming refers to the rise in the Earth’s average temperature due to increasing concentration of greenhouse gases (GHGs) in the atmosphere.
• The atmosphere behaves like a greenhouse, allowing incoming shortwave solar radiation to pass through but absorbing most of the outgoing longwave terrestrial radiation.
• The gases that absorb longwave radiation are called Greenhouse Gases, and the warming effect produced is known as the Greenhouse Effect.
• The concept is similar to a glass greenhouse, where glass is transparent to shortwave radiation but prevents longwave radiation from escaping, causing higher temperature inside.
• Common examples of this effect include a car or bus with closed windows in summer, where heat gets trapped inside.
• The major Greenhouse Gases (GHGs) include Carbon dioxide (CO₂), Chlorofluorocarbons (CFCs), Methane (CH₄), Nitrous oxide (N₂O) and Ozone (O₃).

NCERT Class 11 Physical Geography Chapter 12 provides a clear understanding of global climate systems and emerging climate change concerns. Mastering NCERT Class 11 Physical Geography Chapter 12 helps students connect climatic conditions with vegetation, agriculture and human activities.

A detailed study of NCERT Class 11 Physical Geography Chapter 12 strengthens preparation for environment, geography optional and current affairs related to climate change.

Continue reading NCERT Class 11 Physical Geography Chapter 13 – Water (Oceans) to understand ocean water properties and oceanic processes in a structured and exam-oriented manner.

Frequently Asked Questions (FAQs)

Q1. What is NCERT Class 11 Physical Geography Chapter 12 about?
NCERT Class 11 Physical Geography Chapter 12 explains major world climate types and the concept of climate change.

Q2. Why is NCERT Class 11 Physical Geography Chapter 12 important for exams?
NCERT Class 11 Physical Geography Chapter 12 is important because climate classification and global warming are frequently asked in CBSE and UPSC examinations.

Q3. Which climate types are discussed in NCERT Class 11 Physical Geography Chapter 12?
The chapter discusses equatorial, tropical, temperate and polar climate regions.

Q4. How does NCERT Class 11 Physical Geography Chapter 12 help in UPSC preparation?
NCERT Class 11 Physical Geography Chapter 12 strengthens conceptual clarity about climate systems and environmental change, which are important for Geography and Environment sections.

Q5. Is NCERT Class 11 Physical Geography Chapter 12 linked with later chapters?
Yes, NCERT Class 11 Physical Geography Chapter 12 connects with oceanography and biodiversity topics discussed in later chapters.

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