GEOGRAPHY: FORM FIVE - CLIMATE AND NATURAL REGIONS
CLIMATE AND NATURAL REGIONS
Climate
is the average weather conditions of an area observed and recoded over a
long period of time (about 30 years). This involves systematic
observation, recording and processing of the various elements of climate
such as rainfall, temperature, humidity, air pressure, winds, clouds
and sunshine before any standardization of the climatic means or average
can be arrived at.
Weather:
The conditions of the atmosphere which occur at a place at specific
time period from hour to hour or day to day. The weather should not be
equated with climate, though they are very closely related to each other
in the study of meteorology and climatology. For example when we say
climate of Tanzania is hot wet equatorial climate that is the summing up
of the average everyday weather conditions of the country throughout
the year.
Factors Influencing Climate
1.
Latitude - Influences temperatures on the surface of the earth whereby
the areas nearer to the Equator experience higher temperature than those
far away. -Shifting of the overhead position of the sun is determined
by latitudes and has an influence on climate.
2. Altitude
- Influences temperature and pressure of a region. Low altitude regions
are warmer and experience high atmospheric pressure while high altitude
areas are cooler and have low pressure.
3.
Distance from the sea - Has an influence in both temperature and
rainfall of a region. During summer onshore winds have cooling effect on
the land which is warm. During winter the sea is warmer than the land.
4.
Aspect - Aspect refers to the direction in which a slope faces e.g: in
The Northern Hemisphere, the Southern ward slopes are warmer than the
North ward facing slopes. This is because the North slopes never receive
direct sunshine as the sun in this region never gets overhead. Windward
slopes of highlands receive much higher rainfall than the Leeward
slopes.
5.
Ocean Currents - Current flowing along the Coasts tend to modify the
climate of the Coastal regions. Where onshore wind blow over a cold
ocean current are cooled from the below and the moisture they are
carrying is condensed and dropped over the sea as rain.
6.
Prevailing Winds - Wind is a medium of transfer of heat and moisture
over the land. If wind is blowing from a warm region, it has the warming
effects over the region it is blowing across and if wind will blow from
cold region it will be cold and will cool the land over which it is
blowing.
7.
Human Activities - Like development of settlements, agriculture and
construction of dams and creation of manmade lakes have influence on
climate. In recent times we are realizing the effects of human
activities in causing climate change, caused by:
- clearing of forests
- draining and cultivating swamp areas
- emission of Chlorofluorocarbons and
- other gases from factories and motor vehicles.
CLIMATE AND NATURAL REGIONS OF THE WORLD
Climate is
not the uniform across the World, climate varies from one place to
another. Mainly variation of temperature and rainfall influences
different climatic characteristics. This gives rise to various climatic
regions around the globe.
Natural Regions are
geographical areas with uniform physical characteristics that
distinguish it from other natural regions. The four types of climate are
hot, warm, cool, and cold climates. Each of these climates is further
subdivided into different subtypes as it will be explained in detail
below:
A) HOT CLIMATES
These
are the type of climates found within the tropics, mainly between 23½°
north and 23½° south of the equator. Hot climates include the following
climate sub types:
1. Equatorial climate
2. Tropical continental climate
3. Tropical monsoon climate
4. Tropical marine climate
5. Tropical desert climate
1. EQUATORIAL CLIMATE
Location. The
region is found between 0° and 5° north and south of the equator but in
some regions it may extend up to 10° north or south of the equator.
Examples of areas found within this region include the Amazon basin,
Congo basin, the southern Ivory Coast, south Ghana, western coastal
Nigeria, and eastern coastal Malagasy Republic.
Equatorial Climate |
Climatic Characteristics
1. There are no marked seasons of the year
2. High temperature about 270C throughout the year
3. The annual temperature range is about 3°C.
4. The daily mean temperatures are about 26°C all the year round.
5. The daily temperature range is rarely more than 8°C because of the thick cloud cover.
6. Rainfall is heavy and is usually convection rain.
7. Rainfalls usually occur in the afternoons and they are accompanied by lightning and thunder.
8. The annual rainfall is about 2000mm
9. High humidity and intensive cloud cover throughout the year.
Crops grown are cassava, groundnuts, maize, millet, beans, bananas.
Human activities: Plantation agriculture, fishing, cultivation, peasantry sedentary agriculture.
Common animals found: Monkey, gorillas, crocodiles, and hippopotamus.
NB:
But areas located in highlands 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.
Equatorial Rain forest
|
2. 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:
the region is found between 5° - 15° north and south though it may
extends to 250 north or south of the equator. Area found: East and
Central Africa, Brazilian plateau, Venezuela, Africa and N. Australia.
Climate: hot wet summer season, warm dry winter, rainfall is moderate.
Torrential rainfall associated with thunderstorms in annual range of
temperature increases with the distance from equator.
Climatic Characteristics
1. High temperature, in hot summers (320C) and cooler winters (200C).
2. The annual temperature range is about 110 C.
3. The highest temperatures occur just before the rainy season begins.
4. Heavy rains, mainly convection, occur in the summer.
5.
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.
6. Humidity is high during the hot, wet season.
Vegetation
This climate is characterized by tall grass and trees which are more numerous near the equatorial forest region.
Animals
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.
Tropical or Savannah Climate |
Human Activities
People living in this region mainly engage in livestock keeping, cultivation and tourism. Also lumbering is
practiced. 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.
3. TROPICAL MONSOON CLIMATE
Location.
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.
Climatic Characteristics
1. Seasonal reversal of winds (monsoon winds); onshore during one season and offshore during another season.
2.
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.
3. Temperatures range from 32oC in the hot season to about 25oC in the cool season, giving an annual range of about 7oC.
4. Annual rainfall varies greatly, depending on relief and the angle at which onshore winds meet the highlands (aspect).
5.
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.
Human Activities
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.
4. TROPICAL MARINE CLIMATE
Location. Regions with this type of climate are located on the east coasts of regions lying between 100N and 250N and 100S and 250S.
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.
Climatic Characteristics
1. Temperature characteristics are similar to those of the equatorial climate.
2. Hot season temperature is 290C and cooler season temperature is 210C.
3. Annual temperature range is about 80C.
4. Total annual rainfall varies from 1000 mm to 200 mm depending on the location.
5. Rainfall is both convection and topographic (brought by onshore trade winds).
6. Maximum rainfall occurs in the hot season.
7.
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.
Human Activities
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.
5. TROPICAL DESERT CLIMATE (HOT DESERT)
Location.The tropical desert climate occurs on the western margins of landmasses between latitude 200 to 300 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:
1. Africa: Sahara, Kalahari and Namib Deserts
2. Asia: the desert of Jordan, Syria, Iran, Iraq, Saudi Arabia and Israel, and the desert of India.
3. North America: Mohave, Colorado and Mexican Deserts.
4. South America: Atacama Desert
5. Australia: Great Australian Desert
Vegetation - Hot deserts have clumps of vegetation in which mostly consist of thorny scrub bushes and cacti.
Animals -
the camel is a typical example of a desert animal adapted to its
environment. Other animals which can be found in hot deserts include
donkeys, goats, sheep etc
Human Activities
The bushmen from Kalahari Desert and Aborigines of Australia engage in collecting fruits and hunting. They also eat lizards, insects, snakes and other small animals. People in hot deserts also practise agriculture,
irrigation is practised where oases are found. Some main crops include
maize, millet, rice and wheat. Other human activities are weaving mats,
trading, making tents and ropes
|
Cacti in the Desert |
B) WARM CLIMATES
Warm
climates border the hot tropical deserts. They occur between 300 and
400 north and south of the equator. There are four broad types of warm
climates:
1. Warm temperature western margin.
2. Warm temperature continental.
3. Warm temperature eastern margin.
4. Warm temperature desert.
1. WARM TEMPERATE WESTERN MARGIN (MEDITERRANEAN TYPE)
This is also known as the Mediterranean climate
Location. This type of climate occurs between 300 N and 450 N and 300 S and 400 S
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).
General Characteristics
1. Temperatures range from 210 C in the summer to 100 C (or below) in the winter.
2. Mean annual temperature is about 150C.
3. Annual total rainfall varies from 500 to 900 mm.
4. 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.
Fruit Trees (Mediterranean climate) |
2. 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 200 and 350 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.
Climatic Characteristics
1. Temperatures range from 26oC in the summer to 10oC in the winter.
2. The annual rainfall varies from 380 to 700 mm, depending on the distance from the sea.
3. Rainfall is convectional type and falls mainly in spring and early summer.
Human Activities
The main economic activities carried out in this region are cattle rearing and crop growing. Tourism is also practiced.
3. WARM TEMPERATE EASTERN MARGIN (CHINA TYPE)
Location. It occurs in the eastern sides of the continents between latitudes 230 and 350 north
and south of the equator. The countries having this type of climate are
central China, south eastern USA, and southern Brazil, eastern part of
Argentina, South Africa, southern Brazil, and eastern part of Argentina,
South Africa, southern Japan, and south eastern Australia.
China Type Climate |
Climatic Characteristics
1. Temperatures are about 26°C in summer and 13°C in the winter.
2. The total annual rainfall varies is about 1000 mm.
3. The rain is convectional and torrential type and it mostly falls in the summer.
Human Activities
Temperatures and rainfall in this type of climate make it possible to grow crops and keep animals.
Lumbering is also practiced 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 asmeat, milk, butter and cheese for consumption and
export.
4. 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.
C) COOL CLIMATES
These climates are experienced in regions between 350 north and 600 south
of the equator. They are characterized by definite seasonal variations
in temperature. There are four types of cool climates:
1. Cool temperate continental (British type).
2. Cool temperate continental (Siberian type).
3. Cool temperate eastern margin (Laurentian type).
4. Temperate desert.
1. COOL TEMPERATE WESTERN MARGIN (BRITISH TYPE)
Location. It occurs on the western sides of the continents between 450 and 600 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.
Characteristics
1. Winter temperatures range between 20 C and 70 C, while summer temperatures range from 130 C to 150 C.
3. Rain falls throughout the year, with maxima in winter.
4. The total annual rainfall is about 760 mm.
5. The rain is both convectional and cyclonic in nature.
Human Activities
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 practiced throughout the region.
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 practiced throughout the region.
2. COOL TEMPERATE CONTINENTAL (SIBERIAN TYPE)
Location.
This type of climate is found extensively in the northern hemisphere.
It occurs in the interiors of North America and Eurasia between 350 and 600N
Climatic Characteristics
1. Moderately warm summers (180) and very cold winters (-190C).
2. The annual temperature range is very high (370C).
3. Most of the rain falls in the summer.
4. The rain is convectional type and is often accompanied with thunder.
5. The annual precipitation (rain plus snow) ranges from 400 to 500 mm.
Human Activities
The main human activities in this region include lumbering fishing, mining and some agriculture.
3. COOL TEMPERATE WESTERN MARGIN (LAURENTIAN TYPE)
Location. It occurs on the eastern sides of the continents between 350N and 500N, and south of 400S. It is experienced mainly on the eastern sides of North America and Asia
Climatic Characteristics
1. Winter temperatures range from -100C to 40C.
2. Summer temperatures range from 120C to 240C.
3. The annual temperature range is large and averages 240C.
4. Precipitation (in the form of rain and snow) is distributed throughout the year.
5. Annual precipitation varies between 700 and 1000 mm.
6. Rainfall is both convectional and cyclonic.
Human Activities
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 practiced where minerals are found.
4. TEMPERATE DESERT
Location. This climate occurs in the interiors of Eurasia and North America, and in Patagonia (South America).
Climatic Characteristics
1. Winters are very cold with temperatures often below -70C.
2. Summer temperatures vary between 250C and 370C.
3. Diurnal temperature range is about 350C while the annual temperature range is about 400C.
4. Precipitation is very low, it averages about 250 mm.
5. Most of the rain falls in late winter and early spring.
Human Activities
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. iv.
D) COLD CLIMATES
Cold climates are mainly experienced in regions between latitudes 600 N and 680 N. There are three types of cold climates:
1. Cold temperate western margin.
2. Cold temperate eastern margin.
3. Cold temperate continental.
1. COLD TEMPERATE WESTERN MARGIN
Location. This climate is confined to coastal areas of Scandinavia and Alaska.
Cold Temperate Western Margin |
Climatic Characteristics
1. Cold and long winters with temperatures ranging between -340 C and -450 C.
2. Warm and short summers with average temperatures up to 210 C.
3. Annual rainfall is about 750 mm.
4. Rain falls in most months except the winter when show falls.
Human Activities
The main economic activities practiced in this region include agriculture, mining and manufacturing. A dairy cattle farming is mainly practiced in the Scandinavian countries such as Norway Denmark and Sweden.
2. COLD TEMPERATE CONTINENTAL
Location. This climate occurs between 550N and 680N in the interior of America and Eurasia.
Climatic characteristics
1. Cold and long winters with temperatures ranging between -340 C and -450 C.
2. Warm and short summers with average temperatures up to 210 C.3. Annual precipitation is very low, about 380 mm.
4. Most of the rainfalls in summer, but in winter, precipitation is in the form of snow.
3. COLD TEMPERATE EASTERN MARGIN
This climate occurs in the north east pacific of Russia.
Climatic Characteristics
1. Long, cold winters with an average temperature as low as -200 C or below.
2. Short, hot summers with an average temperature up to 210 C or higher.
3. Total annual rainfall varies between 500 and 1000 mm.
E) ARCTIC CLIMATES
These
types of climates are experienced in regions beyond the Arctic Circle
(661/20 N) and around Arctic Ocean. They are also known as polar
deserts.
The main features of these climates are:
1. Low amounts of precipitation (rain)
2. Mild summers
3. Very cold winters.
Arctic climates comprises of
a) Tundra
b) Polar climates
1. TUNDRA CLIMATE
Location This region occurs in the northern coast of North America, southern coast Greenland and the Arctic coast of Europe and Asia.
Climatic Characteristics
1. Very long, cold winters with temperatures ranging between -290 C and – 400 C.
2. Short, cool summers with temperatures of about 100 C.
3. Annual precipitation is 250 mm; some of it falls as snow in winter and as rain in summer.
2. POLAR CLIMATE
Location. It occurs in the interiors of Iceland, Greenland and Antarctica.
Climatic Characteristics
1. Temperatures are permanently below 00 C.
2. Precipitation is in the form of blizzards (now storms).
3. The winters consist of continuous night, and summers of continuous day.
Bear in Polar Climate |
Human Activities
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.
MOUNTAIN CLIMATE
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.
Climatic Characteristics
1. Pressure and temperature generally decrease with increase in altitude.
2. Precipitation increases with altitude.
3.
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.
Mountain Climate |
Characteristics of these Regions
1. They experience similar problems.
2. They have same geographical back ground.
3. Are unified by the same certain latitudes which help in locating them over.
4. Tend to have almost the same type of soil and vegetation cover.
5. They have the same occupation such as a mining, agriculture and animal husbandry.
We have seen how particular climatic conditions influence human activities. Now, let us see how specific climatic conditions are suitable for given human activities:
1. AGRICULTURE
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.
2. SETTLEMENT
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.
3. FISHING
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.
4. TOURISM
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.
4. INDUSTRY
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.
Industry |
5. TRANSPORT
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
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.
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 twothirds 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:
1.
Increasing concentrations of greenhouse gases in the atmosphere. The
following greenhouse gases which are the main contributors to global
warming:
a) Carbon dioxide
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:
i) 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.
ii) 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.
b) Methane
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.
c) Nitrous Oxide (Dinitrogen Oxide, N2O)
Niitrogen
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.
Producing Nitrous Oxide |
d) Chlorofluorocarbons (CFCs)
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, longlasting and, in many
cases, devastating consequences for planet earth.The following are some
effects of global
warming:
1. 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 biodivers
Increase in Average Temperatures |
2. 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:
i) Higher or lower agricultural yields
ii) Melting of arctic ice and snowcapes- this causes landslides, flash slides and glacial lakes
iii) Extinction of some animal and plant species
iv) Increase in the range of dseases vectors, that is, organism cause diseases like mosquitoes
3. 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.
Change in World’s Climate Patterns |
4. 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.
Rise in Sea Levels |
5. Ocean Acidification
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.
Ocean Acidification |
6. 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.
Deaths of Animals |
7. 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.
Hunger |
The Relationship between Human Activities and Climate
Human activities are human undertakings which are done to earn a living, they include, fishing, lumbering, hunting and gathering and manufacturing. Climate influences human activities directly.E.g In agriculture,
different crops have different requirements of temperature and rainfall
as the major climatic element. Therefore it is not advisable to
cultivate permanent crops in deserts.
Ways of Solving Climatic Problems
There
are natural and man-made causes of climatic change that bring about
climate problems. There are possible solutions to climatic problems such
as:
1. Education
2. Avoidance of bad methods of farming
3. Application of good farming methods
4. Application of appropriate technologies
5. Land reforms
6. Afforestation
7. Laws and rules
8. Reduction of carbon dioxide emissions from industries.
WORLD MAP SHOWING DIFFERENT NATURAL REGIONS
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