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World Climate and Climate Change – Class 11 Geography notes, important questions and MCQs

NCERT Class 11 Geography, chapter 11. Notes, key terms, important questions with answers and MCQs.

Chapter overview

World climates are classified to understand patterns of temperature and rainfall. The most widely used scheme is Köppen's, which uses temperature and precipitation and links climate to vegetation. It has five major groups: A (tropical), B (dry), C (warm temperate), D (cold snow forest) and E (polar), plus H for highlands. Climate has changed in the past, and present global warming, caused mainly by greenhouse gases from human activities, is a major concern.

Köppen's classification

Group A (tropical humid) includes tropical wet (Af), monsoon (Am) and tropical wet and dry or savanna (Aw).
Group B (dry) includes steppe (BS) and desert (BW); Group C includes humid subtropical, Mediterranean (Cs) and marine west coast (Cfb) climates.
Group D (cold, with snow) is found in the Northern Hemisphere interiors; Group E includes tundra (ET) and ice cap (EF); H refers to highland climates.

Climate change

Evidence of past climate change includes glacial deposits, tree rings, ice cores and historical records; the last ice age ended about 10,000 years ago.
Causes include changes in solar output, variations in the Earth's orbit (Milankovitch cycles), volcanic eruptions and greenhouse gas concentrations.
The greenhouse effect is the trapping of terrestrial radiation by gases such as carbon dioxide, methane, nitrous oxide and chlorofluorocarbons; increased emissions cause global warming, melting glaciers and rising sea levels. International efforts include the Kyoto Protocol and the Paris Agreement.

Key terms

Köppen classification: a climate classification based on temperature and precipitation
Greenhouse effect: the trapping of outgoing heat by certain atmospheric gases
Greenhouse gases: gases such as CO2, methane and nitrous oxide that trap heat
Global warming: the rise in the Earth's average temperature
Milankovitch cycles: periodic changes in the Earth's orbit that affect climate

Important questions with answers

What is the greenhouse effect?2 marks

The greenhouse effect is the process by which gases such as carbon dioxide, methane, nitrous oxide and water vapour allow short-wave solar radiation to pass through but absorb long-wave terrestrial radiation, trapping heat in the atmosphere and keeping the Earth warm.

What are the causes of climate change?3 marks

Natural causes include changes in solar output, variations in the Earth's orbit and tilt (Milankovitch cycles) and volcanic eruptions that release aerosols. Human causes include burning fossil fuels, deforestation and agriculture, which increase greenhouse gases and cause global warming.

Describe the causes and effects of global warming.5 marks

Global warming is the gradual rise in the average temperature of the Earth's surface and lower atmosphere. Its main cause is the enhanced greenhouse effect: human activities such as burning coal, oil and gas for energy and transport, deforestation, industrial processes, rice cultivation and livestock rearing have increased the concentration of greenhouse gases such as carbon dioxide, methane, nitrous oxide and chlorofluorocarbons. These gases absorb outgoing long-wave radiation and trap heat in the atmosphere. Since the Industrial Revolution, carbon dioxide levels have risen sharply, and the average global temperature has increased by more than 1°C. The effects include melting of glaciers and polar ice, rising sea levels that threaten coastal areas and islands, changes in rainfall patterns, more frequent and intense heatwaves, droughts, floods and cyclones, shifts in agricultural zones, loss of biodiversity and the spread of some diseases. To address global warming, countries have agreed to the UN Framework Convention on Climate Change, the Kyoto Protocol (1997) and the Paris Agreement (2015), which aim to limit warming by reducing emissions, using renewable energy, increasing forest cover and adapting to changes.

Quick revision

Köppen: A, B, C, D, E, H.
Past climate change: ice ages; evidence.
Causes: solar, orbital, volcanic, greenhouse gases.
Global warming; Kyoto and Paris agreements.

Exam tips

Learn the five Köppen groups with one example region each.
List four greenhouse gases and their sources.

Practice MCQs

The most widely used classification of world climates is by
1. Thornthwaite
2. Humboldt
3. Ratzel
4. Köppen
Show answer
Answer: (d) Köppen. It uses temperature and precipitation.
In Köppen's scheme, the letter B stands for
1. tropical
2. cold snow forest
3. polar
4. dry
Show answer
Answer: (d) dry. It includes deserts and steppes.
Which is a greenhouse gas
1. oxygen
2. nitrogen
3. argon
4. carbon dioxide
Show answer
Answer: (d) carbon dioxide. It traps outgoing heat.
The Mediterranean climate has
1. wet summers and dry winters
2. no rain at all
3. rain all year
4. dry summers and wet winters
Show answer
Answer: (d) dry summers and wet winters. It is coded Cs.
The tundra climate belongs to Köppen group
1. E
2. C
3. D
4. A
Show answer
Answer: (a) E. It is a polar climate.
Periodic changes in the Earth's orbit that affect climate are called
1. El Niño
2. monsoons
3. Milankovitch cycles
4. jet streams
Show answer
Answer: (c) Milankovitch cycles. They help explain ice ages.
Why is the present global warming a concern
1. it is caused only by the Moon
2. it affects only Antarctica
3. it reduces CO2
4. it is linked to rising greenhouse gases from human activities and causes sea-level rise
Show answer
Answer: (d) it is linked to rising greenhouse gases from human activities and causes sea-level rise. Its effects are worldwide.
A monsoon climate in Köppen's scheme is coded
1. Af
2. Am
3. BW
4. ET
Show answer
Answer: (b) Am. It has a short dry season.

All chapters of Class 11 Geography

Written by Kundali IQ from standard, well-established facts to help with revision. This is not an official NCERT publication; always read your textbook too.