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Chapter 11: World Climate and Climate Change - Class 11 Geography Extra Notes

( To be tested through internal assessments in the form of project and presentation) 

Q. Give any three causes of climate change.

Answer:

  • Astronomical causes: Variations in Earth’s orbit, axial tilt, and wobble (Milankovitch cycles).
  • Solar output changes: Sunspot activity affects the amount of solar radiation received.
  • Volcanic eruptions: Release aerosols that block sunlight and temporarily reduce temperature.

Q. Explain the concept of Greenhouse Gases and list their major types.

Answer:

  • Greenhouse gases (GHGs) absorb long-wave radiation emitted from the Earth’s surface and warm the atmosphere.
  • They create a “greenhouse effect”, similar to a glasshouse that traps heat.
  • Human activities have increased their concentration, causing global warming.

Major GHGs:

  • Carbon dioxide (CO₂) – from fossil fuel burning and deforestation.
  • Methane (CH₄) – from agriculture, wetlands, and livestock.
  • Nitrous oxide (N₂O) – from fertilizers and industrial emissions.
  • Chlorofluorocarbons (CFCs) – synthetic gases that also destroy ozone.
  • Ozone (O₃) in lower atmosphere – traps heat effectively.

Q. Describe the main features of climate change during the recent past (20th century).

Answer:

  • 20th century recorded consistent warming, especially in 1901–44 and 1977–99, each showing 0.4°C rise.
  • The global temperature by the end of the century was 0.6°C higher than at the end of the 19th century.
  • Several extreme weather events occurred: severe floods, droughts (e.g., Sahel region).
  • The year 1998 was the warmest year of the millennium.
  • Noticeable retreat of glaciers and rise in sea levels during this period.

Q. Give any three characteristics of Polar (E) climates in Köppen’s classification.

Answer:

  • Mean temperature for all months is below 10°C.
  • Very low precipitation, mostly as snow; extremely cold conditions prevail.
  • Includes Tundra (ET) and Ice Cap (EF) climates, supporting little/no vegetation.

Q. Describe the major climatic groups of Köppen’s classification with their key characteristics.

Answer:
A – Tropical Humid Climates:

  • Mean temperature of coldest month > 18°C
  • High rainfall; low annual temperature range
  • Includes Af, Am, Aw types

B – Dry Climates:

  • Evaporation > precipitation
  • Includes steppe (BS) and desert (BW) climates
  • Large temperature extremes

C – Warm Temperate (Mid-Latitude) Climates:

  • Mild winters; warm summers
  • Occur between 30°–50° latitude
  • Includes Cfa, Cfb, Cwa, Cs

D – Cold Snow Forest Climates:

  • Cold winters (below –3°C)
  • Large annual temperature range
  • Includes Df, Dw

E – Polar Climates:

  • Very cold; mean temperature < 10°C
  • Includes ET (Tundra) and EF (Ice Cap)

Q. Explain any three natural evidences that show climate has changed in the past.

Answer:

  • Glacial landforms: Moraines and U-shaped valleys show repeated advances and retreats of glaciers.
  • Tree rings: Wider rings indicate warm/wet years; narrow rings indicate cold/dry years.
  • Sediments in glacial lakes: Layers of fine and coarse materials reflect alternating warm and cold periods.

Q. State any three reasons why global warming is a major threat to coastal regions.

Answer:

  • Sea level rise due to melting glaciers may flood low-lying coastal areas.
  • Saltwater intrusion into freshwater aquifers can reduce drinking water quality.
  • Increased cyclone intensity may cause destruction of infrastructure and livelihoods.

Q. Explain any three harmful impacts of increasing greenhouse gases in the atmosphere.

Answer (Points):

  • Intensifies the greenhouse effect, raising global temperatures.
  • Disturbs climatic patterns leading to extreme weather, floods, and droughts.
  • Causes thermal expansion of oceans, contributing to sea-level rise.

Q. State any three reasons why climate change is considered a continuous natural process.

Answer:

  • Geological records show alternating glacial and interglacial cycles over millions of years.
  • Historical documents describe periods of cooling and warming (e.g., Little Ice Age).
  • Natural events such as orbital changes, solar variations, and volcanism constantly influence climate.

Q. Give any three reasons for increasing concentration of carbon dioxide in the atmosphere.

Answer (Points):

  • Burning of fossil fuels (coal, oil, natural gas) for industry, transport, and power.
  • Deforestation, reducing CO₂ absorption by vegetation.
  • Agricultural and industrial processes releasing CO₂ as a by-product.

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