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The NCERT Class 11 Geography Chapter 11: World Climate and Climate Change Notes offer a clear understanding of global climate patterns and their transformations. These concise notes cover Koeppen’s classification, detailing tropical, dry, temperate, and polar climates, and explore the causes and impacts of climate change, including global warming and the greenhouse effect. Designed for exam preparation and quick revision, they simplify complex concepts from the Fundamentals of Physical Geography textbook. Ideal for students, these notes enhance comprehension of climate dynamics and environmental challenges. Download the free PDF for effective study and exam readiness.
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Explore Notes of Class 11 Fundamentals of Geography
Introduction
Climate classification organises data on temperature and precipitation for easy analysis. Three approaches, empirical (based on observed data), genetic (based on causes), and applied (for specific purposes), are used. Koeppen’s empirical classification, relating climate to vegetation, is widely used, dividing climates into five major groups: four humid (A, C, D, E) and one dry (B).
Koeppen’s Scheme of Classification of Climate
Koeppen’s classification, developed in 1918, uses mean annual and monthly temperature and precipitation data to classify climates. It employs capital letters (A, B, C, D, E) for major groups and small letters (f, m, w, s, a, b, c, d) for precipitation seasonality and temperature severity. Dry climates (B) are subdivided into steppe (S) and desert (W).
Tropical Humid Climates (A)
- Location: Between the Tropic of Cancer and Capricorn, characterised by hot, humid conditions due to the Intertropical Convergence Zone (ITCZ).
- Types:
- Af (Tropical Wet): Found near the equator (e.g., Amazon Basin, western equatorial Africa). High rainfall year-round, uniform temperatures (30°C max, 20°C min), support tropical evergreen forests.
- Am (Tropical Monsoon): Found in the Indian subcontinent, Northeast South America, Northern Australia. Heavy summer rainfall, dry winter.
- Aw (Tropical Wet and Dry): North and south of Af regions (e.g., Brazil, Sudan). Shorter wet season, longer dry season, supports deciduous forests and grasslands.
Dry Climates (B)
- Characteristics: Low rainfall, inadequate for plant growth, spanning 15°–60° latitudes.
- Subtypes:
- Subtropical Steppe (BSh) and Desert (BWh): Transition zones with sparse grasslands (BSh) or minimal vegetation (BWh). High summer temperatures (up to 58°C recorded in Libya), variable rainfall, and fog in coastal deserts.
- Mid-Latitude Steppe (BSk) and Desert (BWk): Found in continental interiors (35°–60°), with low precipitation due to distance from maritime winds.
Warm Temperate (Mid-Latitude) Climates (C)
- Location: 30°–50° latitudes, on eastern and western continental margins.
- Types:
- Humid Subtropical (Cwa): Warm winters, summer rainfall (e.g., North Indian plains, South China).
- Mediterranean (Cs): Hot, dry summers, mild, rainy winters (e.g., Central California, Central Chile). Precipitation: 35–90 cm.
- Humid Subtropical (Cfa): No dry season, rainfall throughout the year (75–150 cm), found in eastern USA, southern Japan.
- Marine West Coast (Cfb): Moderate temperatures (15°–20°C summer, 4°–10°C winter), precipitation 50–250 cm, found in Northwestern Europe, southern Chile.
Cold Snow Forest Climates (D)
- Location: 40°–70° N in Europe, Asia, and North America.
- Types:
- Cold, Humid Winter (Df): Cold, snowy winters, short frost-free season, large temperature ranges.
- Cold, Dry Winter (Dw): Northeastern Asia, very low winter temperatures, low precipitation (12–15 cm) mostly in summer.
Also Read:
- NCERT Class 6 Geography: Chapter 5 Major Domains of the Earth
- NCERT Class 7 Geography Chapter 3 ‘Our Changing Earth’: Notes and Solutions (Free PDF)
Polar Climates (E)
- Location: Beyond 70° latitude.
- Types:
- Tundra (ET): Permafrost, low-growing vegetation (mosses, lichens), short growing season.
- Ice Cap (EF): Below freezing even in summer, minimal precipitation, found in Greenland, Antarctica.
Climate Change
Climate has varied naturally over geological time, with glacial and inter-glacial periods. Evidence includes geomorphological features, sediment deposits, and tree rings. India experienced wet conditions around 8,000 B.C., and the Harappan civilisation (3,000–1,700 B.C.) thrived in a wetter Rajasthan.
Climate in the Recent Past
Climate in the Recent Past highlights significant climatic variations and temperature trends over recent centuries. These concise notes cover extreme weather events, historical climatic shifts, and warming trends.
- Variability: The 1990s recorded the warmest temperatures of the century, with extreme weather events like global floods, showcasing significant climatic variability.
- Notable Events: The Sahel drought (1967–1977) devastated regions south of the Sahara, while the 1930s Dust Bowl caused severe drought in the southwestern Great Plains, USA.
- Historical Trends: Europe experienced warm, dry conditions in the 10th–11th centuries, enabling Viking settlement in Greenland, followed by the Little Ice Age (1550–1850) with colder conditions.
- Temperature Rise: From 1885–1940, global temperatures showed an upward trend. The 20th century warmed by 0.6°C, with the seven warmest years in the last decade, 1998 being the warmest.
Causes of Climate Change
The Causes of Climate Change examines factors driving climatic shifts. These concise notes cover astronomical and terrestrial causes, including sunspot cycles, Milankovitch oscillations, volcanism, and greenhouse gas emissions. Here are some of the causes of climate change:
- Astronomical Causes:
- Sunspot Cycles: Variations in sunspot activity affect solar output. More sunspots correlate with cooler, wetter weather, while fewer sunspots lead to warmer, drier conditions, though statistical significance is limited.
- Milankovitch Oscillations: Changes in Earth’s orbit, axial tilt, and wobble alter insolation, influencing long-term climate patterns.
- Terrestrial Causes:
- Volcanism: Eruptions (e.g., Pinatubo, El Chichon) release aerosols, reducing solar radiation reaching Earth, temporarily cooling the planet.
- Greenhouse Gas Emissions: Increased CO2 from fossil fuel combustion and deforestation, along with methane, CFCs, nitrous oxide, and ozone, trap long-wave radiation, causing global warming.
- Greenhouse Effect: GHGs absorb Earth’s emitted long-wave radiation, warming the atmosphere. CO2, rising 0.5% annually, is the primary contributor, with a 20–50-year adjustment period.
- Human Impact: Deforestation reduces CO2 sinks, increasing atmospheric concentrations. Industrial activities and fossil fuel use amplify GHG emissions, intensifying climate change.
Global Warming
Global warming is the increase in Earth’s temperature due to rising greenhouse gas concentrations, primarily CO2 from fossil fuel combustion and deforestation. These gases trap long-wave radiation, warming the atmosphere. Impacts include sea level rise from melting glaciers and thermal expansion, threatening coastal areas and ecosystems. The Kyoto Protocol aims to reduce emissions to mitigate global warming. Here are the terms explained under global warming.
- Greenhouse Effect: GHGs (CO2, CFCs, methane, nitrous oxide, ozone) trap long-wave radiation, warming the Earth. CO2, from fossil fuel combustion and deforestation, is the primary contributor.
- Impact: Rising CO2 (0.5% annually) may double pre-industrial levels, warming the planet. Ozone depletion (e.g., Antarctic ozone hole) allows more UV radiation. Sea level rise from melting glaciers and thermal expansion threatens coastal areas.
- Mitigation: The Kyoto Protocol (1997, effective 2005) aims to reduce GHG emissions by 5% below 1990 levels by 2012.
Also Read:
- NCERT Class 6 Geography: Chapter 3 Motions of the Earth
- NCERT Class 6 Geography: Chapter 1 The Earth in the Solar System
Important Definitions in NCERT Notes Class 11 Geography Fundamentals of Physical Geography Chapter 11: World Climate and Climate Change
Here we have explained the key concepts and terms of this chapter to make it easy for you to understand.
- Empirical Classification: Based on observed temperature and precipitation data.
- Genetic Classification: Organizes climates by their causes.
- Applied Classification: For specific purposes.
- Koeppen’s Classification: Empirical system using temperature, precipitation, and vegetation, with capital (A, B, C, D, E) and small letters (f, m, w, s, a, b, c, d).
- Tropical Humid Climates (A): Hot, humid, high rainfall, found near the equator.
- Dry Climates (B): Low rainfall, includes steppe (BS) and desert (BW).
- Warm Temperate Climates (C): Warm summers, mild winters, found in mid-latitudes.
- Cold Snow Forest Climates (D): Cold winters, found in high northern latitudes.
- Polar Climates (E): Tundra (ET) and Ice Cap (EF), beyond 70° latitude.
- Greenhouse Effect: Trapping of long-wave radiation by GHGs, warming the Earth.
- Global Warming: Increase in Earth’s temperature due to rising GHG concentrations.
- Ozone Hole: Depletion of stratospheric ozone, allowing UV radiation to reach the surface.
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FAQs
Koeppen’s empirical classification uses temperature, precipitation, and vegetation data, dividing climates into five groups (A, B, C, D, E) with subtypes based on precipitation and temperature characteristics.
Climate change is caused by astronomical factors (sunspots, Milankovitch oscillations) and terrestrial factors (volcanism, GHG emissions). CO2 from fossil fuels and deforestation is a major driver of global warming.
The greenhouse effect occurs when GHGs (e.g., CO2, methane) trap long-wave radiation emitted by the Earth, warming the atmosphere, similar to heat retention in a glass greenhouse.
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