Concept of Climate
Climate is the average weather conditions of an area observed and recorded over a long period of time (about 30 years).
The scientific study of climate is called climatology and a person who studies climate is called climatologist.
Weather and Climate
The Difference between Weather and Climate
There are marked differences between weather and climate. The table below summarizes these differences.
|Describes the atmospheric conditions at a specific place and time.||Describes the average atmospheric conditions of a place over a specific period of time.|
|Weather is defined as the day to day state of the atmosphere, and it is short-term (minutes to weeks) variation.||Climate is defined as statistical weather information that describes the variation of weather at a given place for a specified time interval.|
|Weather conditions are measured over a short period e.g. a few hours or days.||Climate conditions are measured over many years, e.g., 30 years.|
|Determined by real time measurements of atmospheric pressure, wind speed and direction, humidity, precipitation, cloud cover, and other variables.||Determined by averaging weather data over periods of 30 years.|
|Weather changes abruptly within a short period.||Climate changes slowly and gradually over many years.|
|Weather varies from one place to another within a region.||Climate remains uniform over a large area.|
|Most weather elements are measured by weather instruments.||Climatic elements are not measured but calculated from the recorded weather data.|
Factors influencing weather and climate
Usually, the elements of weather (which make up climate) vary from place to place. In the lesson on weather we learned about the elements of weather. Because climate is influenced by weather, the elements of weather are the same as the elements of climate. Therefore, the factors that cause variation in weather elements will likewise influence the climate. The factors influencing climate and weather are discussed below:
Latitude:This factor influences temperature and rainfall. Areas around and close to the equator experience higher temperature and receive higher rainfall than those farther away. So the rainfall and temperature decreases as one moves away from the equator.The amount of heat received at any place on the earth’s surface depends on the angle at which the sun’s rays strike the surface of the earth and the duration of the sunshine. At the equator, the sun’s rays fall on the Earth’s surface at almost right angles throughout the year, but the angle at which the sun’s rays strike the Earth’s surface decreases as one moves towards the poles.Therefore, temperatures decrease with increase in latitude because the equator receives vertical rays of sunlight while the north and the south poles receive slanting rays. Because of this fact, the equator and places near the equator are hotter while places in or near the south and north poles are colder.
Altitude:This influences temperature and atmospheric pressure of an area. Temperature decreases with increasing altitude at the rate of 0.6°C for every 10 metres rise in altitude. Therefore, low-altitude areas are warmer than high altitude areas. Atmospheric pressure decreases with increasing altitude. Pressure at sea level is higher than pressure at the summit of a high mountain.
Ocean currents:The nature of the ocean current influences the temperature of the wind blowing over it and transfers this influence to the land adjacent to the ocean. This will either lead to reduction or increase in the temperature of the land depending on the type of the ocean current. The wind blowing over warm ocean currents will pick moisture from the ocean and often causes heavy rainfall over the land while the wind blowing over the cold ocean current brings little or no rainfall to the land.
Distance from the sea:This influences temperature and rainfall. Places located near the sea experience high temperature and receive high rainfall than those located farther away. This is because of high rates of evaporation from the water surface, which eventually causes heavy rainfall along the coastal areas. For this reason, coastal regions often experience higher temperatures and rainfall than inland areas.
Aspect:This term refers to the direction in which a slope faces. It influences temperature and rainfall. For example, the south facing slopes in the northern hemisphere are always warmer than the north-facing slopes. Also the windward side of the mountain receives heavier rainfall than the leeward side.
Wind and air masses:Wind carries moisture with it as it flows. Warm wind blowing over a cold region warms the cold region over which it flows. However, if the wind is cold, it cools the region.Warm, moist wind blowing towards a cold, dry region may lead to formation of rainfall in the destination region. Cold, dry wing blowing over a dry region brings no rainfall and if the blowing is repeated over several years, it may cause aridity in that region.
Alignment of the coastline:This refers to the arrangement of the region’s coastline in relation to the direction of the wind. If the winds blow across the coastline they cause rainfall. If they blow in parallel to the coastline, they cause drought.
Intertropical Convergence Zone (ITCZ):This is a low-pressure area around the equator. The moist winds meet within this region. Places farther away from this zone experience only one rainy season while places close to the zone experience two seasons of heavy rainfall. This is because the winds converge around this region twice a year.
Forests:Areas covered with forests normally receive high rainfall as compared to those with little or no vegetation. This is because of high rates of evaporation and transpiration, leading to high humidity. Therefore, these areas often, receive high amounts of rainfall and have a modified climate.
Human activities:A range of human activities such as agriculture, mining, transportation, construction, etc affects the climate. For instance, clearing of the forests to get land for agriculture and settlement leads to the loss of biodiversity, making the land arid and unproductive.
Impact of Climate
Relationship between Climate and Human Activities
Relate climate to human activities
Climate has many impacts to human activities. Various economic activities conducted by man in different parts of the world are governed by the type of climate experienced in a particular region. For example, people living in deserts and semi-arid regions do not practice much agriculture because their environment does not favour crop cultivation or animal husbandry. In these regions, however, a very limited agriculture and animals rearing is conducted. The animals kept include camels, goats, sheep, donkeys and other hardy animals. Only drought resistant crops such as dates are grown in deserts and arid areas.
In tropical and equatorial regions, a lot of agriculture is carried out. The inhabitants of these regions take part in cultivation of crops and keeping of animals. Crops grown include cocoa, banana, horticultural crops and grains. The animals kept in these climatic zones include cattle, pigs, donkeys, horses, poultry and other farmyard animals. Specific types of various economic activities carried out in each climatic region will be discussed in detail in the section below.
THE MAJOR WORLD CLIMATIC REGIONS
Different regions of the world experience different amount of temperature and rainfall. The differences in the amount of rainfall and temperature experienced in different regions of the world make them have different climatic characteristics. This gives rise to various climatic regions around the globe. Temperature and rainfall are the main elements that determine the type of climate. Both elements vary considerably from one region to another and form a basis for classifying climate. The five broad types of climate are hot, warm, cool, cold and arctic (very cold) climates. Each of these climates is further subdivided into different subtypes as it will be explained in detail below:
These are the type of climates found within the tropics, mainly between 23?° north and 23?° south of the equator. Hot climates include the following climate sub types:
Tropical continental climate
Tropical monsoon climate
Tropical marine climate
Tropical desert climate
The region is found approximately between 0° and 5° north and south of the equator. It may extend up to 10° north or south of the equator in some regions. Examples of areas found within this region include the Amazon basin (South America), and the Congo basin, the southern Ivory Coast, south Ghana, western coastal Nigeria, and eastern coastal Malagasy Republic (all in Africa).
There are no marked seasons.
High temperature throughout the year: – The annual temperature range is about 3°C. – The daily mean temperatures are about 26°C all the year round.
The daily temperature range is rarely more than 8°C because of the thick cloud cover.
Rainfall is heavy and is usually convection rain.
Rainfalls usually occur in the afternoons and they are accompanied by lighting and thunder.
Total annual rainfall is about 200 mm with two maxima (peaks).
High humidity and intensive cloud cover throughout the year This climate can generally be described as hot and wet throughout the year, with a small annual temperature range.
Highlands located within the equatorial region have their temperatures modified by altitude. The temperature of some of these highland areas, e.g., the East African Highlands, is lowered to about 15°C. These regions are said to have a modified equatorial climate.
Variations on the basic type of climate occur in the highland regions of equatorial Africa. The climate of most of these regions has an equatorial rainfall pattern.
In areas such as the south-eastern Nigeria, Cameroon, the south-east Asian islands of Malaysia, Indonesia and the Philippines, the climate is equatorial monsoon because of the seasonal reversal of winds. This results in even heaver rainfall.
Human activities carried out in the equatorial climate region include shifting cultivation and plantation agriculture. Crops grown in this region include yams, cassava, maize, millet, sweet potatoes, sorghum, beans, water melons, bananas and groundnuts. Examples of areas where this type of farming is practiced include some parts of West Africa and Asia.
In plantation agriculture, crops such as cocoa, rubber and oil palms are grown on large scale farms. Most rubber plantations are found in Malaysia, Indonesia, Thailand and Srilanka. They are also found in Liberia. Cocoa plantations are found in Brazil and West Africa (Ghana, Nigeria and Ivory Coast). Oil palms are grown in Nigeria, Malaysia and Indonesia.
Rainforests are also common in equatorial regions. In Africa, the equatorial forests are found in the Democratic Republic of Congo (RDC), Gabon and some parts of West Africa.
Tropical continental climate
This climate is also known as Sudan type or Savannah climate. In the interior of the continents it is referred to as tropical continental climate.
Location: This climatic region occurs between 5oN and 15oN and 5oS and 15oS though it extends to 25o north or south of the equator. It is best developed in most parts of Africa, and some parts of South America, India and Australia.
Hot summers (32oC) and cooler winters (21oC).
The annual temperature range is about 11oC.
The highest temperatures occur just before the rainy season begins.
Heavy rains, mainly convection, occur in the summer.
Total annual rainfall is around 765mm, though this increases in the areas lying close to the equatorial climate region. Similarly, rainfall decreases towards the tropical deserts.
Humidity is high during the hot, wet season.
This climate is characterized by tall grass and trees which are more numerous near the equatorial forest region. The savannah region is suitable for herbivores animals such as giraffes, elephants, buffaloes, rhino, zebras, antelopes, wildebeests and many other animals. There are also carnivorous animals such as lions, leopards, hyenas, etc. The region also supports a variety of species of birds, reptiles and insects.
People living in this region mainly engage in livestock keeping, cultivation and tourism. Also lumbering is practised. Many tourists come from foreign countries to view the wildlife that live in the vast grassland. Numerous national parks have been established in this region. In Tanzania, for example, there are established national parks such as Serengeti, Mikumi, Selous, Tarangire, Ruaha, Saadani, Ngorongoro, Katavi and Manyara.
The major crops grown in this region are maize, millet, groundnuts, beans, onions, cotton, tobacco, sugarcane, sisal, rice and coffee.
Tropical monsoon climate
The areas which mainly experience monsoon type of climate are South East Asia, Northern Australia, Southern China, and the Indian subcontinent. This type of climate is most marked in India.
Seasonal reversal of winds (monsoon winds); onshore during one season and offshore during another season.
Onshore wind brings heavy rain to coastal regions while offshore winds bring little or no rain, except where they cross a wide stretch of the sea.
Temperatures range from 32ºC in the hot season to about 25ºC in the cool season, giving an annual range of about 7ºC.
Annual rainfall varies greatly, depending on relief and the angle at which onshore winds meet the highlands (aspect).
There are three marked seasons: cool, dry season; hot, dry season; and hot, wet season.
This climate can generally be described as having a hot, wet season and cool, dry season. The main human activities carried out in areas experiencing this type of climate include rice growing and livestock husbandry. Apart from rice, the other crops grown are wheat, millet, maize, and sorghum.
Sugarcane, cotton and juice are important lowland crops grown in India, Pakistan and Bangladesh. The other crops grown are tea (Sri-lanka, Bangladesh and India) and rubber in Malaysia. Animals kept in this climatic region include pigs, cattle, buffalos, sheep, goats, and poultry.
Tropical marine climate
Regions with this type of climate are located on the east coasts of regions lying between 10oN and 25oN and 10o S and 25oS. These areas are under the influence of onshore trade winds. The main areas are the east coasts of Brail and Malagasy, the lowlands of central American and the west indies the coast of Queen land (Australia) and the southern Islands of the Philippines.
Temperature characteristics are similar to those of the equatorial climate.
Hot season temperature is 29ºC and cooler season temperature is 21ºC. (c) Annual temperature range is about 8ºC.
Total annual rainfall varies from 1000 mm to 200 mm depending on the location.
Rainfall is both convection and topographic (brought by onshore trade winds).
Maximum rainfall occurs in the hot season.
High humidity throughout the year.
This climate can generally be described as hot and humid throughout the year. However, the climate is cooled by the onshore winds blowing almost everyday.
The main human activities carried out in this climatic region include crop cultivation, lumbering and animal rearing. The crops grown include sugarcane, rice, banana and wheat. The animals kept are such as cattle, pigs, sheep, goats and poultry.
Tropical desert climate
The tropical desert climate occurs on the western margins of landmasses between latitude 20o to 30o north and south of the equator. The climate is experienced in all the major tropical deserts of the world. The hot deserts occupy about one third of the earth’s surface.
The principal tropical deserts occur on the continents as follows:
Africa: Sahara, Kalahari and Namib Deserts.
Asia: the desert of Jordan, Syria, Iran, Iraq, Saudi Arabia and Israel, and the desert of India.
North America: Mohave, Colorado and Mexican Deserts.
South America: Atacama Desert.
Australia: Great Australian Desert
Very little total annual rainfall (less than 120 mm in any one year).
Mean monthly temperatures range from 29ºC in the hot season to 10ºC in the cool season.
In most deserts, daytime temperature can rise to as high as 47ºC or more.
Night temperatures can fall to as low as 16ºC in summer and 5ºC in winter.
Very high diurnal temperature range (due to very hot days and very old nights).
The annual temperature range is large. It is about 16ºC.
Humidity is always low and therefore evaporation is high.
Desert environments support very minimal human activities. Wherever water is available as in oases (singular oasis), and along rivers, agriculture is practised. The crops grown include date palms, cotton, rice, sugarcane, vines, millet, tomatoes, tobacco and fruits. Apart from the people who live permanently in oases, there are nomads who move from one place to another in search of pasture.
They keep camels, donkeys, goats and sheep. The camel is an animal that has adapted to desert conditions. It can survive for many days without drinking water. It is mainly used for transport in the desert. Other desert people are good hunters and also collect food from the bushes.
The other activities that can be done by desert dwellers include weaving mats, making ropes, and trading.
Warm climates border the hot tropical deserts. They occur between 30o and 40o north and south of the equator.
There are four broad types of warm climates:
Warm temperature western margin;
Warm temperature continental;
Warm temperature eastern margin; and
Warm temperature desert.
Warm temperate western margin (Mediterranean type). This is also known as the Mediterranean climate
This type of climate occurs between 30oN and 45oN and 30oS and 40oS on the western sides of the continents. Places experiencing the Mediterranean climate are on the coastal lands around the Mediterranean Sea (the Maghreb, Spain, Italy, Greece, Egypt and Israel), the western sides of north and South America (central California and central Chile), South Australia (Perth and Adelaide) and South Africa (Cape Province).
Temperatures range from 21ºC in the summer to 10ºC (or below) in the winter.
Mean annual temperature is about 15ºC.
Annual total rainfall varies from 500 to 900 mm.
Hot, dry summers and cold, wet winters. This is because westerly winds blow off shore in the summer and on shore in the winter.
The Mediterranean climate can generally be described as having hot, dry summers and middy, rainy winters.The climate permits a wide range of crops to be grown, which include fruits and cereals. It is in this region that much of the world’s citrus fruits are grown. Citrus fruits include oranges, lemons, grapes and limes. Other fruits grown here are peaches, apricots, plums, cherries, olives, almonds and pears.
The cereals include maize, wheat, rice and barley. Agriculture has given rise to specialized industries such as wine-making, flour-milling, fruit canning and food processing industries.
Warm temperate continental (steppe type)
This type of climate is also known as warm temperate interior region.
Location: It occurs in the interior of the continents, between 20o and 35o north and south of the equator. The best examples of the areas having this climate are Murray-Darling lowlands of Australia; The high Veldt of South Africa; and the central Paraguay and central Argentina (both in South America); central lowlands of north America (Oklahoma and Texas and in northern Mexico); central European lowlands, and the plains of Manchuria.
Temperatures range from 26ºC in the summer to 10ºC in the winter.
The annual rainfall varies from 380 to 700 mm, depending on the distance from the sea.
Rainfall is convectional type and falls mainly in spring and early summer. The main economic activities carried out in this region are cattle rearing and crop growing. Tourism is also practised.
Warm temperate eastern margin (China type)
Location: It occurs in the eastern sides of the continents between latitudes 23o and 35o north and south of the equator. The countries having this type of climate are central China, south eastern USA, southern Brazil, eastern part of Argentina, South Africa, southern Brazil, eastern part of Argentina, South Africa, southern Japan, and south eastern Australia.
Temperatures are about 26oC in summer and 13oC in the winter.
The total annual rainfall varies is about 1000 mm.
The rain is convectional and torrential type and it mostly falls in the summer.
Temperatures and rainfall in this type of climate make it possible to grow crops and keep animals. Lumbering is also practised in the forested areas. The crops grown include rice, maize, cotton, sugarcane and tobacco. Animals are extensively kept in Argentina and Australia. The animals produce products such as meat, milk, butter and cheese for consumption and export.
Warm temperate desert
This type of climate is also called mid-latitude desert climate. The areas having this type of climate include Nevada and Utah states of North America and Pentagonia in South America. It is also found in regions that extend from Turkey, northern Iran, across the Caspian sea and Aral areas into former USSR. It is also experienced in the Gobi desert of Mongolia.
These climates are experienced in regions between 35o north and 60o south of the equator. They are characterized by definite seasonal variations in temperature. There are four types of cool climates:
Cool temperate continental (British type);
Cool temperate continental (Siberian type);
Cool temperate eastern margin (Laurentian type); and
Cool temperate western margin (British type)
It occurs on the western sides of the continents between 45o and 60o north and south of the equator. Areas with this type of climate include North West Europe, British Columbia in western Canada, Southern Chile, Tasmania, and the south Island of New Zealand.
Winter temperatures range between 2ºC and 7ºC, while summer temperatures range from 13ºC to 15ºC.
The annual temperature range is between 8ºC and 11ºC.
Rain falls throughout the year, with maxima in winter.
The total annual rainfall is about 760 mm.
The rain is both convectional and cyclonic in nature.
People living in this region engage in a myriad of economic activities which include agriculture, mining, lumbering, manufacturing and commerce. Agriculture is of extensive type and includes keeping of beef and dairy cattle and sheep and the growing of wheat, barley oats, vegetables and fruits. In British Columbia lumbering is an important economic activity. In Tasmania and New Zealand, sheep rearing for wool and mutton is an important activity. Fruit farming, especially apples, is practised throughout the region.
Cool temperate continental (Siberian type)
This type of climate is found extensively in the northern hemisphere. It occurs in the interiors of North America and Eurasia between 35º and 60ºN
Moderately warm summers (18º) and very cold winters (-19ºC).
The annual temperature range is very high (37ºC).
Most of the rain falls in the summer.
The rain is convectional type and is often accompanied with thunder.
The annual precipitation (rain plus snow) ranges from 400 to 500 mm.
The main human activities in this region include lumbering fishing, mining and some agriculture.
Cool temperate western margin (Laurentian type)
It occurs on the eastern sides of the continents between 35oN and 5oN, and south of 40oS. It is experienced mainly on the eastern sides of North America and Asia.
Winter temperatures range from -10ºC to 4ºC.
Summer temperatures range from 12ºC to 24ºC.
The annual temperature range is large and averages 24ºC.
Precipitation (in the form of rain and snow) is distributed throughout the year.
Annual precipitation varies between 700 and 1000 mm. (f) Rainfall is both convectional and cyclonic.
The main economic activities in this region are farming, mining, and manufacturing. The crops grown include wheat, maize, millet and soya beans. Sheep farming is important in Patagonia. Mining and manufacturing are practised where minerals are found.
This climate occurs in the interiors of Eurasia and North America, and in Patagonia (South America).
Winters are very cold with temperatures often below -7ºC.
Summer temperatures vary between 25ºC and 37ºC.
Diurnal temperature range is about 35ºC while the annual temperature range is about 40ºC.
Precipitation is very low, it averages about 250 mm.
Most of the rain falls in late winter and early spring.
The human activities carried out in this region include mining, animal rearing and some agriculture. The animals reared are such as camels, donkeys, sheep and goats. The main crops grown in this region are date palms, oil palms, and millet. Agriculture is mostly practised in oases and along river valleys.
Cold climates are mainly experienced in regions between latitudes 60ºN and 68ºN
There are three types of cold climates:
Cold temperate western margin;
Cold temperate continental; and
Cold temperate eastern margin.
Cold temperate western margin
This climate is confined to coastal areas of Scandinavia and Alaska.
Short, cold summers with temperatures of about 12ºC.
Long winters with temperatures ranging from -2ºC to 4ºC.
Annual rainfall is about 750 mm.
Rain falls in most months except the winter when show falls.
The main economic activities practiced in this region include agriculture, mining and manufacturing. Dairy cattle farming is mainly practiced in the Scandnavian countries such as Norway Denmark and Sweden.
Cold temperate Continental
This climate occurs between 55oN and 68oN in the interior of America and Eurasia.
Cold and long winters with temperatures ranging between -34ºC and -45ºC.
Warm and short summers with average temperatures up to 21ºC.
Annual precipitation is very low, about 380 mm. (d) Most of the rainfalls in summer, but in winter, precipitation is in the form of snow.
Cold temperate eastern margin
This climate occurs in the north east pacific of Russia.
Long, cold winters with an average temperature as low as -20ºC or below.
Short, hot summers with an average temperature up to 21ºC or higher.
Total annual rainfall varies between 500 and 1000 mm.
These types of climates are experienced in regions beyond the Arctic Circle (661/2oN) and around Arctic Ocean. They are also known as polar deserts. The main features of these climates are low amounts of precipitation (rain), mild summers and very cold winters.
Arctic climates comprises of Tundra and Polar climates
This region occurs in the northern coast of North America, southern coast Greenland and the Arctic coast of Europe and Asia.
Very long, cold winters with temperatures ranging between -29ºC and – 40ºC.
Short, cool summers with temperatures of about 10ºC.
Annual precipitation is 250 mm; some of it falls as snow in winter and as rain in summer.
It occurs in the interiors of Iceland, Greenland and Antarctica.
Temperatures are permanently below 0ºC.
Precipitation is in the form of blizzards (now storms).
The winters consist of continuous night, and summers of continuous day.
Because temperatures are very low, most these regions are uninhabited and hence limited human activities take place here. The natural occupations are hunting, fishing and herding of reindeer.
This type of climate occurs in the main mountain areas of the world. The areas that experience such climates include the East Africa Mountains, the Ethiopian highlands, the mountains and plateaus of central Asia, the Alps of Europe, the Andes of South America and the Rockes of North America.
Pressure and temperature generally decrease with increase in altitude.
Precipitation increases with altitude.
In areas around mountains within the tropic, temperatures may range from high at the foot of a mountain to very cold at the peak, e.g. Mount Kilimanjaro.
We have seen how particular climatic conditions influence human activities. Now, let us see how specific climatic conditions are suitable for given human activities.
Agriculture is strongly influenced by weather and climate. The nature of agriculture and farming practices in any particular location depends on the type of climate experienced in that location.
Crops thrive well in any area with a fertile soil and which receives sufficient rainfall as well as optimum temperature conditions. In such areas both commercial and subsistence crops may be grown.
The equatorial region receives high rainfall and experiences high temperature throughout the year. This climate is suitable for crops that can thrive well in moist and hot conditions. The crops that can be grown in this region include cocoa, banana, rubber, sugarcane and yams.
Livestock rearing can be practised in the tropics where rainfall permits the growth of pastures. This area also supports the cultivation of a variety of tropical crops such as fruits, tobacco, sugarcane, tea, maize, rice and a variety of horticultural and cereal crops
Cooler climates also support crops which grow better in climates like barley, wheat, oats, sugar beet, and fruits such as apples, peaches and apricots. These areas also support the rearing of dairy animals.
In semi desert and desert climates where very little rainfall is received, there are reduced agricultural activities. However, drought-resistant crops like millet, date palms, oil palms and sorghum can be grown. The keeping of hardy animals such as sheep, camels, donkeys and goats can be done.
People like to establish settlements in areas with favourable climates and which support a variety of agricultural activities. Such areas are often well-populated. Very hot or extremely cold areas are usually sparsely populated because their climatic conditions are unfavourable for human settlement.
Forests thrive well in areas that receive ample rainfall and which have adequate temperatures. Dense forests of the world are concentrated in the equatorial and tropical climates which experience high rainfall and temperature throughout the year. The presence of forests in these regions stimulate lumbering and growth of other industries such as paper-making and carpentry.
Most of the world’s fishing grounds are in cooler regions. The cooler water is thought to support the growth of water plants called plankton on which fish feed. Tropical areas are not suitable for fish as compared to regions with temperate climates.
For tourism industry to flourish, the climate in the host countries must be favourable enough to attract the tourists to visit them. Tropical countries, like Tanzania, are often visited by tourists from cooler climates during winter in their home countries to enjoy the warmth of the tropical countries where they swim in warm waters and sunbath in tropical beaches.
Likewise, the tropical climate supports numerous wildlife which serve as tourist attractions. In Tanzania, for example, there are many national parks with thousands of wildlife species and beautiful sceneries. The animals found in the parks include elephants, buffaloes, zebras, lions, leopards, chimpanzees, monkeys and a variety of reptiles, amphibians, insects and plant species.
The establishment and growth of industries strongly correlate to the climatic conditions. Most industries are established in areas where raw materials are adequately available. For instance, milk, tea, tobacco, meat, fish and fruit processing industries are often located where raw materials are found. Likewise, lumbering industries are built close to forests.
Development of the transport systems in some climatic regions is very difficult. For example, the tropical and equatorial regions, which receive much rainfall throughout the year, have poorly developed roads. Routes passing through areas with clay soils become muddy and slippery when it rains.
This makes it hard to travel on earthy and murram roads. Roads in desert regions may be blocked by sand blown onto them, making the roads impassable. In very cold regions, precipitation in the form of snow may cover roads, making them impassable during winter.
Climate change is a large-scale, long term shift in the planet’s climate (weather patterns and temperatures). The overall effect of climate change is termed as global warming.
Question Time 1
What is global warming?
Global warming refers to increase of the earth’s average surface temperature due to effects of the greenhouse gases. These gases trap heat that would otherwise escape from the earth. The greenhouse gases include water vapour (H2O), carbon dioxide (CO2), methane (CH4), dinitrogen oxide or nitrous oxide (N2O), ozone (O3) and chlorofluorocarbons (CFCs).
Since the early 20th century, the global air and sea surface temperature has increased by about 0.8°C, with about two-thirds of the increase occurring since 1980. Each of the last three decades has been successively warmer at the earth’s surface than preceding decades since 1850.
The recent rapid warming was caused by human activities which contribute to the production of greenhouse gases, such as carbon dioxide, that trap heat in the earth’s atmosphere. It is predicted that the continuation of these activities will result in 1.8–4°C average temperature increase over the next century.
Causes of global warming
Scientific understanding of the cause of global warming has been increasing. Global warming is mostly caused by increasing concentrations of greenhouse gases in the atmosphere. The following greenhouse gases are the main contributors to global warming. They are the main causes of global warming.
Carbon dioxide is the main greenhouse gas. The gas contributes over 50% of the greenhouse effect. It is because of this reason that man is struggling to reduce carbon dioxide emissions. The following are some of the man-made sources of carbon dioxide in the atmosphere:
Deforestation: Green plants absorb carbon dioxide gas from the atmosphere and use it to manufacture their food through the process of photosynthesis. Cutting down trees means that a few trees are left to absorb carbon dioxide gas from the air. This has led to the increase in the amount of carbon dioxide in the atmosphere.
Combustion of fuel: Burning of fossil fuel such as wood, coal, petroleum and natural gas, releases carbon dioxide into the atmosphere. The gas is produced during combustion of these fuels in car engines, power stations, industries, etc.
The main source of methane is from agricultural activities. It is released from wetlands such as rice fields and from animals, particularly cud-chewing animals, like cattle. The emission of methane gas into the atmosphere, therefore, increases with increase in agricultural activities. Since 1960s the amount of methane in the air has increased by 1% per year, twice as fast as the build-up of carbon dioxide. Methane is also produced by the decomposition of waste materials by bacteria. It is the major component of natural gas. The gas is also produced during the mining of coal and oil (as natural gas) and when vegetation is burnt.
Dinitrogen oxide is produced from both man-made and natural processes. Human activities which produce dinitrogen oxide include combustion of fossil fuels in vehicles and power stations, use of nitrogenous fertilizers and burning of vegetation and animal waste. During combustion of fuel in automobile engines, the air gets so hot that nitrogen reacts with oxygen to form dinitrogen oxide.
The gas is also produced by digesting bacteria, and is part of the nitrogen cycle, one of the most important natural processes on earth.
The sources of CFCs in the atmosphere include refrigerators, air conditioners and aerosols. CFCs are extremely effective greenhouse gases. One CFC molecule is about 10,000 times more effective in trapping heat than a carbon dioxide molecule. Some of them are up to 14,000 times effective than carbon dioxide, the main greenhouse gas.
Effects of global warming
Global warming is expected to have far-reaching, long-lasting and, in many cases, devastating consequences for planet earth. The following are some effects of global warming:
Increase in average temperatures
One of the most immediate and obvious impacts of global warming is the increase in temperatures on the world. The average global temperature has increased by about 0.8°C over the past 100 years. Scientists predict that the earth’s average temperature will increase by between 1.4 and 5.8°C by the year 2100.
Increase in global temperature will affect both the land and the ocean environments. The average temperature of the oceans has increased significantly in the past few decades, causing negative effects on marine life.
When the ocean water gets warm, the algae in the ocean tends to produce toxic oxygen compounds called superoxides which are damaging for the corals. Global warming is threatening the coral reefs to a great extent, and the fact is that if coral reefs are wiped off the planet, it will affect one third of planet’s marine biodiversity, as well as other ecosystems related to the coral reefs directly or indirectly.
Extreme weather events
Extreme weather events include record-breaking high or low temperatures, floods or intense storms, droughts, heat waves, hurricanes and tornadoes, etc. These are effective measures of climate change and global warming.
Scientists project that extreme weather events, such as heat waves, droughts, blizzards and rainstorms will continue to occur more often and with greater intensity due to global warming.
Other effects of extreme weather events include:
higher or lower agricultural yields;
melting of arctic ice and snowcaps. This causes landslides, flash floods and glacial lake overflow;
extinction of some animal and plant species; and
increase in the range of disease vectors, that is, organisms that cause diseases.
Change in world’s climate patterns
It is forecasted that global warming will cause climate patterns worldwide to experience significant changes. Climate change resulting from increasing temperatures will likely include changes in wind patterns, annual precipitation and seasonal temperature variations.
Climatic patterns in most parts of the world have already changed. Rains fall when least expected and at irregular intervals. This has greatly affected the timing of planting and harvesting activities. Sometimes the rains fall so heavily to cause floods, or too little leading to drought.
Most of the arable land that once used to be productive is slowly turning arid. With time, farmers will run short of the land for cultivation, a fact that will result in famine.
Because high levels of greenhouse gases in the atmosphere are likely to remain high for many years, these changes are expected to last for several decades or longer.
Rise in sea levels
Continued increase in the global temperature will cause the melting of ice caps in the poles and mountain glaciers. Melting polar ice and glaciers are expected to raise sea levels significantly. Global sea levels have risen about 8 inches since 1870 and the rate of increase is expected to accelerate in the coming years. If current trends continue, many coastal areas will eventually be flooded.
Scientists predict that by the year 2100 the sea level will raise by at least 25 m, leading to coastal flooding that will displace millions of people. Small islands in the Caribbean, South Pacific, Mediterranean and Indian Ocean will be totally covered by ocean waters.
As levels of atmospheric carbon dioxide increase, the oceans absorb some of it. This increases the acidity of seawater. Since the Industrial Revolution began in the early 1700s, the acidity of the oceans has increased about 25%.
Because acids dissolve calcium carbonate, seawater that is more acidic has a drastic effect on organisms with shells made of calcium carbonate, such as corals, mollusks, shellfish and plankton. The acid water is likely to dissolve the carbonaceous shells, thus endangering the lives of these sea creatures. Change in ocean acidity will also affect fish and other aquatic animals and plants.
If current ocean acidification trends continue, coral reefs are expected to become increasingly rare in areas where they are now common.
Effects on plants and animals
The effects of global warming on the earth’s ecosystems are expected to be profound and widespread. Many species of plants and animals are already moving their range northward or to higher altitudes as a result of warming temperatures. Additionally, migratory birds and insects are now arriving in their summer feeding and nesting grounds several days or weeks earlier than they did in the 20th century.
Warmer temperatures will also expand the range of many disease-causing pathogens that were once confined to tropical and subtropical areas, killing off plant and animal species that formerly were protected from disease.
These and other impacts of global warming, if left unchecked, will likely contribute to the disappearance of up to one-half of the earth’s plants and one-third of animals from their current range by 2050.
Effects on humans
As dramatic as the effects of climate change are expected to be on the natural world, the projected changes to human society may be even more devastating.
Agricultural systems will likely be affected badly. Though growing seasons in some areas will expand, the combined impacts of drought, severe weather, lack of snowmelt, greater number and diversity of pests, lower groundwater tables and a loss of arable land could cause severe crop failures and livestock shortages worldwide.
This loss of food security might, in turn, create havoc in international food markets and could spark famines, food riots, political instability and civil unrest worldwide.
The effect of global warming on human health is also expected to be serious. An increase in mosquito-borne diseases like malaria and dengue fever, as well as a rise in cases of chronic conditions like asthma, are already occurring, most likely as a direct result of global warming.