World Climate And Climate Change Class 11 Notes Geography Chapter 11 - CBSE

Chapter : 11

What Are World Climate And Climate Change ?

  • Three broad approaches have been adopted for classifying climate. They are empirical, genetic, and applied.
  • Koeppen identified a close relationship between the distribution of vegetation and climate. He selected certain temperature and precipitation values, related them to vegetation distribution and used these values for classifying the climates.
  • Climatic Groups According to Koeppen:
Group Characteristics
A - Tropical The average temperature of the coldest month is 18°C or higher
B - Dry Climates Potential evaporation exceeds precipitation
C - Warm, Temperate The average temperature of the coldest month of the (Mid-latitude) climates years is higher than -3°C but below 18°C
D - Cold Snow forest The average temperature of the coldest month is minus 3°C or below
E - Cold Climates Cold Climates Average temperature for all months is below 10°C
H - Highlands Cold due to elevation
  • Koeppen introduced the use of capital and small letters to designate climatic groups and types. The capital
    letters: A, C, D, and E delineate humid climates and B indicates dry climates. The climatic groups are subdivided into types designated by small letters, based on the seasonality of precipitation and temperature characteristics. The seasons of dryness are indicated by the small letters: f, m, w, and s.
Group Type Letter Code Characteristics
A - Tropical Humid Climate Tropical wet
Tropical monsoon
Tropical wet and dry
No dry season
Monsoonal, short dry season
Winter dry season
B - Dry Climate Subtropical Steppe
Subtropical desert
Mid-latitude steppe
Mid-latitude desert
Low-latitude semiarid or dry
Low-latitude arid or dry
Mid-latitude semiarid or dry
Mid-latitude arid or dry
C - Warm temperate (Mid-latitude) Climates Humid subtropical
Marine west coast
No dry season, warm summer
Dry hot summer
No dry season, warm and cool summer
D - Cold snow forest Climates Humid contionental Subarctic Df
No dry season, severe winter
Winter dry and very severe
E - Cold Climates Tundra
Polar ice cap
No true summer
Perennial ice
H - Highland Highland H Highland with snow cover
  • The tropical group is divided into three types, namely:
    • Af: Tropical wet climate
    • Am: Tropical monsoon climate
    • Aw: Tropical wet and dry climate
  • Dry climates (Group-B) are divided into steppe or semiarid climates (BS) and desert climate (BW). They are further subdivided as subtropical steppe (BSh) and subtropical desert (BWh) at latitudes from 15°–35° and mid-latitude steppe (BSk) and mid-latitude desert (BWk) at latitudes between 35°–60°.
  • Warm Temperate (Mid-Latitude) Climates-C: Warm temperate (mid-latitude) climates extend from 30°–
    50° of latitude, mainly on the eastern and western margins of continents. They are grouped into four types:

(i) Humid subtropical, i.e., dry in winter and hot in summer (Cwa)

(ii) Mediterranean (Cs)

(iii) Humid subtropical, i.e., no dry season and mild winter (Cfa)

(iv) Marine west coast climate (Cfb)

  • Cold Snow Forest Climates (D): Cold snow forest climates are divided into two types:

(i) Df- cold climate with humid winter

(ii) Dw- cold climate with dry winter

The severity of winter is more pronounced in higher latitudes.

  • Highland climates (H) are governed by topography. In high mountains, large changes in mean temperature occur over short distances. Precipitation types and intensity also vary spatially across highlands.
  • Ozone Hole: The depletion of ozone concentration in the stratosphere is called the ozone hole.
  • Greenhouse gases: The gases that absorb long-wave radiation are called greenhouse gases.
  • Greenhouse effect: The processes that warm the atmosphere are often collectively referred to as the
    greenhouse effect.
  • Daily range of temperature: The difference between the highest and lowest temperatures of a place in a
    day is called the daily range of temperature.
  • Dust bowl: During the 1930s, a severe drought occurred in the southwestern Great Plains of the United States.
    These are described as the dust bowl.
  • Greenhouse: The term greenhouse derives from the analogy to a greenhouse used in cold areas to preserve
    heat. A greenhouse is made up of glass. The glass, which is transparent to incoming short-wave solar radiation,
    is opaque to outgoing long-wave radiation.