World Climate and Climate Change

Learning Outcomes

1. Understand the various classifications of world climate.
2. Comprehend the causes and effects of climate change.
3. Identify the different types of climates as per Koeppen’s scheme.
4. Grasp the concept of global warming and its implications.

Climate Classification Approaches

The study of world climate involves organizing information into smaller, manageable units for easy understanding. There are three main approaches to classifying climates: empirical, genetic, and applied. Each approach focuses on different aspects of climate study.

1. Empirical Classification: This method is based on observed temperature and precipitation data. It is widely used due to its reliance on actual measurements.
2. Genetic Classification: This approach organizes climates according to their causal factors, such as the distribution of pressure systems, wind patterns, and ocean currents.
3. Applied Classification: This type is designed for specific purposes, such as agriculture or environmental management.

Koeppen’s Climate Classification Scheme

One of the most well-known and widely used empirical classification systems is Koeppen’s scheme. Developed by V. Koeppen, it relates closely to vegetation and uses temperature and precipitation data to categorize climates. This scheme, established in 1918 and later modified, remains relevant and widely applied.

Koeppen’s Climate Groups:

1. Group A: Tropical Climates: The average temperature of the coldest month is 18°C or higher. This group includes regions with high rainfall and year-round warmth.
2. Group B: Dry Climates: In these areas, potential evaporation exceeds precipitation, creating arid environments like deserts and steppes.
3. Group C: Warm Temperate Climates: The average temperature of the coldest month falls between −3°C and 18°C.
4. Group D: Cold Snow Forest Climates: Here, the coldest month’s average temperature is below −3°C, and winters are typically harsh.
5. Group E: Cold Climates: The average temperature is below 10°C for all months, characterizing polar regions.
6. Group H: Highland Climates: These climates occur at elevations where temperature decreases with altitude.

Key Subdivisions:

1. f: No dry season.
2. m: Monsoon climate.
3. w: Winter dry season.
4. s: Summer dry season.

Dry Climates (Group B) are further divided based on precipitation:

• S for steppe (semi-arid) climates.
• W for desert (arid) climates.

Tropical Humid Climates (Group A)

These climates, located between the Tropic of Cancer and the Tropic of Capricorn, are hot and humid due to the overhead position of the sun and the presence of the Intertropical Convergence Zone (ITCZ). There are three types of tropical humid climates:

1. Af: Tropical Wet Climate: This climate is found near the equator, where there is no dry season, and rainfall is heavy throughout the year. Major areas include the Amazon Basin and western equatorial Africa.
2. Am: Tropical Monsoon Climate: Found in the Indian subcontinent, North-East South America, and Northern Australia, this climate has a distinct dry winter and wet summer.
3. Aw: Tropical Wet and Dry Climate: Occurring north and south of Af regions, this climate is characterized by a shorter wet season and longer dry periods, with variable rainfall.

Dry Climates (Group B)

Dry climates, characterized by low rainfall, cover a vast area extending between 15° and 60° latitudes north and south of the equator. These climates are typically found in regions dominated by subtropical high-pressure systems or areas blocked by mountains from moist maritime winds.

Subdivisions:

1. Subtropical Steppe (BSh): Located in transition zones between humid and dry climates, this region receives enough rainfall to support sparse grasslands.
2. Subtropical Desert (BWh): Extremely arid, with highly variable rainfall, these regions experience intense heat during summer and fog in coastal deserts near cold currents.
3. Mid-Latitude Steppe (BSk): Occurring at higher latitudes, this climate supports semi-arid grasslands with less precipitation than subtropical steppe.
4. Mid-Latitude Desert (BWk): These deserts experience cold winters and minimal precipitation due to their location within continents or behind mountain ranges.

Warm Temperate (Mid-Latitude) Climates (Group C)

Warm temperate climates are found between 30° and 50° latitudes, on the eastern and western edges of continents. They generally feature warm summers and mild winters.

Types of Warm Temperate Climates:

1. Humid Subtropical Climate (Cwa): Found in the North Indian plains and South China, this climate has dry winters and hot summers, similar to Aw, but with warmer winters.
2. Mediterranean Climate (Cs): Found around the Mediterranean Sea, California, and Chile, this climate is known for its hot, dry summers and mild, rainy winters.
3. Humid Subtropical (Cfa): Present in Eastern USA, China, and Japan, this region experiences rainfall throughout the year with thunderstorms in summer.
4. Marine West Coast Climate (Cfb): Located on the western coasts of continents, such as in Europe, North America, and New Zealand, this climate is moderated by marine influence, with precipitation throughout the year.

Cold Snow Forest Climates (Group D)

These climates, confined to the Northern Hemisphere between 40° and 70° latitudes, experience long, cold winters with snow cover and short frost-free seasons. They are divided into:

1. Df: Cold Climate with Humid Winters: This climate is found in areas such as Northern Europe and Canada where winters are snowy and summers are mild.
2. Dw: Cold Climate with Dry Winters: Occurring in Northeastern Asia, this climate experiences extremely cold winters and moderate summers with monsoon-like winds.

Polar Climates (Group E)

Polar climates are found poleward of 70° latitude and include two main types:

1. Tundra Climate (ET): This region is known for permafrost and supports only low-growing plants like mosses and lichens during the short growing season.
2. Ice Cap Climate (EF): Found in Greenland and Antarctica, these regions remain frozen year-round, with minimal precipitation. The movement of icebergs characterizes this climate.

Highland Climates (Group H)

Highland climates are unique because they are determined by elevation rather than latitude. The variation in temperature and precipitation depends on the altitude and topography, with climates changing vertically as one ascends or descends a mountain range.

Important Note: The vertical zonation in highland climates leads to a diversity of conditions that can mirror different global climate zones at various altitudes.

Climate Change

Climate change refers to the long-term changes in the Earth’s climate patterns. Throughout Earth’s history, climate has fluctuated between glacial and interglacial periods, as evidenced by geological records, tree rings, and sediment deposits.

Causes of Climate Change

1. Astronomical Causes: These include changes in solar output due to sunspot activity and the Milankovitch cycles involving variations in Earth’s orbit, axial tilt, and precession, which influence the amount of solar radiation received by the Earth.
2. Terrestrial Causes: Volcanic eruptions release aerosols into the atmosphere, which can reflect sunlight and temporarily cool the Earth’s surface.
3. Human Activities: The most significant cause of recent climate change is the increased concentration of greenhouse gases (GHGs), which trap heat in the atmosphere and contribute to global warming.

Table 1: Key Greenhouse Gases and Their Sources

Global Warming

Global warming is the gradual increase in Earth’s surface temperature due to the enhanced greenhouse effect. The main contributors to global warming are CO2, CH4, N2O, and CFCs.

Important Concept: The greenhouse effect is essential for maintaining Earth’s habitable temperature. However, the excessive accumulation of greenhouse gases amplifies this effect, leading to higher temperatures.

The consequences of global warming include:

1. Rising Sea Levels: The melting of glaciers and polar ice caps, along with the **

thermal expansion** of seawater, leads to higher sea levels, threatening coastal areas.

2. Climate Extremes: Increased temperatures can lead to more frequent and severe heatwaves, droughts, and storms.
3. Ecosystem Disruption: Changes in temperature and precipitation patterns affect biodiversity and ecosystem stability.

Kyoto Protocol and International Efforts

The Kyoto Protocol, established in 1997 and enforced in 2005, was a significant step in reducing global GHG emissions. Industrialized nations agreed to cut their emissions to levels 5% below those of 1990 by 2012.

Important Note: Continued international cooperation is necessary to address climate change and mitigate its adverse effects on global life systems.

MCQ
Which of the following gases is most responsible for trapping heat and contributing to global warming?
Answer: Carbon dioxide (CO2).