Fundamental Of Physical Geography Chapter 12 World Climate And Climate Change

The ancient Greeks divided the earth into three regions:

i. Winterless tropical regions.

ii. The summerless polar regions.

iii. Intermediate regions having both winter and summer.

The characteristics are: 
i. The tundra climate is so called after the types of vegetation, like low growing mosses, lichens and flowering plants.

ii. This is the region of permafrost where the sub soil is permanently frozen.

iii. The short growing season and water logging support only low growing plants.

iv. During summer, the tundra regions have very long duration of day light.

The characteristics are: 
i. As the name suggests, Mediterranean climate occurs around Mediterranean sea, along the west coast of continents in subtropical latitudes between 30° - 40° latitudes e.g. — Central California, Central Chile, along the coast in south eastern and south western Australia.

ii. These areas come under the influence of sub tropical high in summer and westerly wind in winter.

iii. Hence, the climate is characterised by hot, dry summer and mild, rainy winter.

iv. Monthly average temperature in summer is around 25° C and in winter below 10°C.

v. The annual precipitation ranges between 35 - 90 cm.

The features:

i. Tropical wet climate is found near the equator. The major areas are the Amazon Basin in South America, western equatorial Africa and the islands of East Indies.

ii. Significant amount of rainfall occurs in every month of the year as thunder showers in the afternoon.

iii. The temperature is uniformly high and the annual range of temperature is negligible.

iv. The maximum temperature on any day is around 30°C while the minimum temperature is around 20°C.

v. Tropical evergreen forests with dense canopy cover and large biodiversity are found in this climate.

The world can be divided into the following zones:

i. Torrid zones between 0°-30°N latitudes with a mean temperature of 20°C

ii. Temperate zone

iii. Frigid zone.

The climatic groups are: 
i. Tropical - Average temperature of the coldest month is 18° C or higher.
ii. Dry Climates - Potential evaporation exceeds precipitation.
iii. Warm Temperate - The average temperature of the coldest month of the (Mid-latitude) climates years is higher than minus 3°C but below 18°C.
iv. Cold Snow Forest Climates - The average temperature of the coldest month is minus 3° C or below.
v. Cold Climates - Average temperature for all months is below 10° C.
vi. High Land - Cold due to elevation. 

International efforts have been initiated for reducing the emission of GHGs into the atmosphere.

i. The most important one is the Kyoto protocol proclaimed in 1997.

ii. This protocol went into effect in 2005, ratified by 141 nations.

iii. Kyoto protocol bounds the 35 industrialised countries to reduce their emissions by the year 2012 to 5 percent less than the levels prevalent in the year 1990.

Genetic classification : It emphasises causes or origin or their formation based on weather processes.

Empirical classification : It is based on observation related factors for climatic differentiation.

ii. ‘Aw’: ‘Aw’ belongs to the tropical wet and dry climate. It is dominated by dry trade winds. In this region, average precipitation is less than the one in tropical wet climate. The winters are dry seasons. This type of climate is called Savanna climate because of the tall grasses that grow between trees and thorny bushes.

i. Boreal: It belongs to E Type. The boreal climate is found in higher mid-latitudes. In this climate summers are short and cool, winters are long and cold with a very short frost-free season. Annual range of temperature is between 0° to 10°C and rainfall is meagre and most of it occurs during summers. It is found in coniferous forests of the world.

Highland Climates:

i. Highland climates are governed by topography.

ii. In high mountains, large changes in mean temperature occur over short distances.

iii. Precipitation types and intensity also vary spatially across high lands. There is vertical zonation of layering of climatic types with elevation in the mountain environment.

The gases that absorb long-wave radiation are called greenhouse gases. The processes that warm the atmosphere are often collectively referred to as greenhouse effect.

The greenhouse gases are:

1. Carbon dioxide

2. Cholorofluro carbons (CFCs)

3. Methane (CH₄)

4. Nitrous Oxide (N₂0)

5. Ozone and some other gases such as nitric oxide and carbon monoxide.

Volcanism is considered as another cause for climate change.

i. Volcanic eruption throws up lots of aerosols into the atmosphere.

ii. These aerosols remain in the atmosphere for a considerable period of time reducing the sun’s radiation reaching the Earth’s surface.

iii. After the recent Pinatoba and El Cion volcanic eruptions, the average temperature of the earth fell to some extent for some years.

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Plants use carbon dioxide and sunlight to make their own food and grow. The carbon becomes part of the plant. Plants that die and are buried may turn into fossil fuels made of carbon like coal and oil over millions of years. When humans burn fossil fuels, most of the carbon quickly enters the atmosphere as carbon dioxide.

Carbon dioxide is a greenhouse gas and traps heat in the atmosphere. Without it and other greenhouse gases, Earth would be a frozen world.
But humans have burned so much fuel that there is about 30% more carbon dioxide in the air today than there was about 150 years ago, and Earth is becoming a warmer place.
In fact, ice cores show us that there is now more carbon dioxide in the atmosphere than there has been in the last 420,000 years.