# WBBSE Class 10 Geography Solutions Chapter 2.3 Heat, Temperature and Global Warming

Detailed explanations in West Bengal Board Class 10 Geography Book Solutions Chapter 2.3 Heat, Temperature and Global Warming offer valuable context and analysis.

## WBBSE Class 10 Geography Chapter 2.3 Question Answer – Heat, Temperature and Global Warming

Answer in short : 2 Marks

Question 1.
What is ‘insolation’?
Answer:
According to H.C. Gitchfield, radiant energy from the sun that strikes the earth is called insolation. Insolation is received in the form of shortwaves. The amount of insolation that comes to the earth’s surface is only one part of two hundred crore parts of the sun’s heat.

Question 2.
What is albedo?
Answer:
A very little fraction of the sun’s energy comes to the earth as insolation, of which the total energy is not absorbed by the earth. 34% of the insolation is reflected back to space by the dust, ice crystals and cloud present in the atmosphere. This is called ‘albedo’.

Question 3.
What is heat budget?
Answer:
The incoming solar radiation is balanced by an equal amount of outgoing radiation returned from the earth. This balance maintained between the insolation and outgoing radiation is called the ‘heat budget of the earth.’

Question 4.
How is the heat balance of the earth maintained ?
Answer:
The average temperature of the earth remains same more or less throughout the year. The 66% of insolation received during day time is radiated back during the night. Thus, although there may be some seasonal variations, total balance of heat throughout the year is never disturbed. This is how the heat balance of the earth is maintained.

Question 5.
What is the ‘normal lapse rate of temperature’?
Answer:
In the troposphere, the temperature of the atmosphere is inversely proportional to the altitude of a place. With every 1 km or 1000 m rise in altitude, temperature reduces by 6.4°C. This is known as the ‘normal lapse rate of temperature’.

Question 6.
On what factors does the amount of insolation depend?
Answer:
The insolation depends on several factors like – (a) length of day (b) distance between the sun and the earth (c) clarity of the atmosphere (d) angle of incidence of solar rays etc.

Question 7.
What do you mean by ‘inversion of temperature’?
Answer:
By the normal lapse rate, temperature reduces by 6.4°C with every 1 km rise in altitude. But in some cases, it is seen that temperature increases with increase in height. This phenomenon is known as the inversion of temperature. This is common in valleys of mountainous regions during early morning and late nights.

Question 8.
What do you mean by the ‘diurnal range of temperature’ ?
Answer:
The range of temperature between the maximum and minimum temperatures recorded in a single day is called the diurnal range of temperature.

Question 9.
What do you mean by Average or Mean temperature ?
Answer:
The average between the highest and lowest temperatures recorded in a day is called the average or mean temperature.

Question 10.
What is ‘Mean monthly temperature’ ?
Answer:
The average of the mean temperatures of all the days of a month is known as the mean monthly temperature.

Question 11.
What do you mean by the annual range of temperature?
Answer:
Annual range of temperature is the difference between the mean temperatures of the hottest and coldest months of the year.

Question 12.
What is average annual temperature?
Answer:
The average of the mean temperatures of all the months of the year is known as the average annual temperature.

Question 13.
What do you mean by Katabatic winds?
Answer:

Cold air in steep and deep valleys descends down and accumulates at the bottom due to gravity during the night. Such winds by which the cold air is forced to lie below the warm air is called Katabatic winds.

Question 14.
What do you mean by Anabatic winds?
Answer:

Cold air descends into valley bottoms during the night due to Katabatic winds. During day time, this air is gradually heated and warmed. This warm air starts rising along the valley walls. This is known as Anabatic winds.

Question 15.
Name the different temperature zones of the world.
Answer:
The different temperature zones of the world are :

1. The Torrid zone.
2. The North Temperature zone.
3. The South Temperate zone.
4. The North Frigid zone.
5. The South Frigid zone.

Question 16.
What do you mean by temperature zones or belts ?
Answer:

Temperature of the earth’s atmosphere tends to change significantly along with change in latitudes from the equator towards the poles. The earth being round, these latitudinal zones having similar temperature conditions can be demarcated as spherical belts or zones. These are known as temperature zones.

Question 17.
What is a isotherm ?
Answer:
Isotherms are imaginary lines drawn on a map joining places of the same average temperature for a specified period, supposing the places to be reduced to the sea level.

Question 18.
What is global warming ?
Answer:
Global warming is the process of gradual increase of the general temperature of the earth due to increase in the use of green house gases and many other reasons. Temperature of the earth has increased by 1° from 1900 to 2000 .

Question 19.
Name some green house gases.
Answer:
Some green house gases are : Carbon dioxide (C2), Carbon monoxide (CO), Methane (CH4), Nitrous Oxide (N2O), Chloro fluoro carbon (CFC), Water vapour (H2O), Ozone (O3) etc.

Question 20.
What is El Nino?
Answer:
El Nino refers to the large scale ocean-atmospheric climatic interaction linked to a periodic warming in sea surface temperatures across the central and eastcentral equatorial Pacific Ocean. The effects of El Nino disturbs the global distribution of rainfall and temperature and also affect the seasons.

Question 21.
What is Solar constant?
Answer:
The rate at which energy reaches the earth’s surface from the Sun through perpendicular rays, usually taken to be 1388 watts per sq. meter is called solar constant.

Question 22.
What is the heat equator?
Answer:
Heat equator or thermal equator is a imagenary belt encircling the earth connects all places having highest mean annual temparature at each longitude around the globe. This line roughly followed the 5° North latitude.

Question 23.
What is Six’s maximum and minimum thermometer?
Answer:
It is a instrument measuring the temperature of the day in terms of maximum and minimum value. So that it helps to calculate the average temparature and the diurnal range of temperature.

Question 24.
What is effective solar radiation?
Answer:
The earth receives one part of two hundred crore parts of sun’s radiation. Of this, about 34% of the heat energy is reflected back to space as Albedo. The remaining 66% of the heat energy that heats up the earth’s surface directly or indirectly is called Effective Solar Radiation.

Question 25.
Why does the atmosphere get heated maximum at 2 pm. even though the vertical solar rays reach the earth’s surface at 12 noon?
Answer: The most important process of heating the atmosphere is radiation by the earth’s surface. Although the earth receives maximum heat through the vertical rays of the sun at around 12 noon, the rate of radiation is maximum at 2 p.m. Hence, the atmosphere gets heated to its maximum during this time.

Question 26.
Name the hottest and coldest places of the earth.
Answer:
The hottest place of the earth is Al Azizia of Libya in Africa (58°C). The coldest place is Vostok of Antarctica (-88°C).

Question 27.
When does a place experience the highest and lowest temperatures in a day?
Answer:
In a day, the highest temperature is experienced around 2 p.m. and the lowest temperature is experienced just before sunrise.

Question 28.
What do you mean by Torrid Zone?
Answer:
The zone spreading from $$23^{1 / 2}$$°N (Tropic of Cancer) to $$23^{1 / 2}$$° S (Tropic of Capricorn is known as the Torrid Zone. It is the hottest zone of the world.

Question 29.
What do you mean by the Temperate Zone?
Answer:
The zone lying between the Tropic of Cancer ($$23^{1 / 2}$$° N) and Arctic Circle ($$66^{1 / 2}$$° N) in the northern hemisphere and the zone between the Tropic of Capricorn ($$23^{1 / 2}$$° O) and Antarctic Circle ($$66^{1 / 2}$$° S) in the southern hemisphere are known as the Temperate Zones.

Question 30.
What do you mean by the Frigid Zone?
Answer:
The zone lying between the Arctic Circle ($$66^{1 / 2}$$° N) and the North Pole (90^{\circ N) in the northern hemisphere and the zone between the Antarctic Circle ($$66^{1 / 2}$$° S) and the South Pole (90° S) in the southem hemisphere are called Frigid zones.

Question 31.
What do you mean by Green House effect?
Answer:
The increasing concentration of green house gases in the atmosphere like Carbon dioxide, Methane, Chloro fluoro carbon, water vapour, ozone etc. are increasing the general temperature of the atmosphere by absorbing and holding back more and more heat. This gradual process of increasing the atmospheric temperature in general is called global warming, which is the outcome of Green House effect.

Answer in brief : 3 Marks

Question 1.
Differentiate between heat and temperature of the atmosphere.
Answer:

 Heat Temperature i. Heat is an energy. i. Temperature is the measure of the condition of heat of any object. ii. Heat leads to change of temperature. ii. Temperature is the result of heat. iii. Two objects having same temperature may have different heat contents. iii. Two objects having same heat content may have different temperatures. iv. Measured in calories or joules with the help of calorimeter. iv. Measured in degree centigrade or fahrenheit with the help of thermometers.

Question 2.
Why does temperature decrease with increase in altitude?
Answer:

Atmospheric temperature decreases with increase in altitude for the following reasons :

1. Insolation first heats up the earth’s surface. This heat is radiated into the atmosphere gradually heating the layers from bottom to top.
2. The upper layers of the atmosphere are less dense and can rapidly radiate out heat and get cooled.
3. Pressure is less in the upper levels of the air, hence their heat absorbing capacity is also less.
4. The dust and other particles present in the upper layers absorb most of the heat and hence the air remains cool.

Question 3.
Why is lowest temperature recorded during dawn or early morning ?
Answer:
The earth takes almost the whole night to radiate back the insolation that it receives during the day time. Hence it becomes coolest during the early morning or dawn, before the insolation of the next day starts.

Question 4.
What are the importances of temperature in the atmosphere?
Answer:
The importances of temperature in the atmosphere are:

1. Temperature helps in birth, growth and other activities of living things on the earth.
2. It helps in germination of seeds.
3. Difference in temperature in different regions of the earth brings about growth of different species of plants and animals in different regions of the world.
4. Rate of evaporation, formation of clouds, rainfall, snowfall etc. depend on temperature conditions of a place.
5. Difference in temperature of different places leads to difference in air pressure, hence leads to generation of winds.

Question 5.
Why is annual range of temperature of deserts very high?
Answer:
The reasons for great difference of temperature between hottest and coldest months in deserts are as follows :
(i) Deserts are composed of sand particles containing quartz which absorb and release heat very quickly. Hence extremes of temperature are seen.
(ii) Lack of vegetation in deserts attract very less rainfall. Hence extreme temperatures are seen.
(iii) The sandy soil of deserts have very less water holding capacity. Hence the soil gets heated very quickly and also release heat very quickly.

Question 6.
Explain the process of radiation in heating the earth’s atmosphere.
Answer:
The insolation received by the earth comes in the form of short wave radiations and reach the earth’s surface without heating the atmosphere much. When this heat is radiated back by the earth in the form of long waves, it is easily absorbed by the air surrounding it. This terrestrial radiation helps to heat up the atmosphere to the maximum.

Question 7.
What is the role of conduction in heating the atmosphere ?
Answer:
Conduction is the process in which one particle transmits heat to another particle. Air is a poor conductor of heat and only the lower layers of the atmosphere are heated by conduction. Thus, it is a less significant process of heating the atmosphere.

Question 8.
What is Convection?
Answer:
Transfer of heat by the movement of a mass or substance from one place to another is called convection. The air particles being heated from their contact with the earth’s surface become lighter and rise. The comparatively cool air particles in the upper layers are heavier and come down slowly. This process form air currents that are known as convection currents.

Question 9.
What is Advection?
Answer:
Advection is the process by which the hot air moves along the earth’s surface horizontally and heats up the cool air of some other place. By this process, the heat of the lower latitudes is transmitted towards the higher latitudes. This process may affect temperatures of adjacent local areas as well. Eg. – ‘Loo’ is transmitted by the process of advection.

Question 10.
What are the effects of El Nino?
Answer:
The effects of El Nino are :

1. Occurrence of El Nino considerably reduces rainfall in the south-east Asian countries, Indonesia, Australia and regions near the Indian ocean.
2. Rainfall occurs in Peru and Atacama desert region of South America.
3. Warm ocean curents influenced by the El Nino warm up the waters near the coastal region of Peru. Thus planktons cannot survive. This harms fish accumulation and fish catch.
4. It obstructs the blowing of monsoon winds, thus reducing rainfall.
5. It causes the weather of the western hemisphere to become warmer than normal.
6. The corals and other sea creatures may get killed.

Question 11.
What are the effects of La Nina ?
Answer:
The effects of La Nina are :

1. La Nina causes heavy rainfall in western part of Pacific ocean, south and eastern Asia and north and eastern Australia.
2. In the southern hemisphere, the months from December to February remain much moist and the equatorial region in Africa remains comparatively drier.
3. Tropical cyclones increase in South and Eastern Asia.
4. Severe droughts persist in Peru and adjacent areas in South America.
5. North-western parts of North America receive more rainfall than normal.
6.  Canada experiences severe cold winters.

Question 12.
Why is lowest temperature experienced during very early morning or just before dawn?
Answer:
The earth receives insolation throughout the day and radiates it back after sunset. It takes almost the whole night to radiate back all the heat before it starts receiving heat once again the next day. Hence, the atmosphere remains coolest during the dawn and very early morning, and the lowest temperatures are recorded during this time.

Question 13.
What are isotherms ? What are its characteristics?
Answer:
Isotherms are imaginary lines drawn on weather maps to join places having the same temperature at the same time. The characteristics of isotherms are:

1. The isotherms run almost parallel to the latitudes.
2. They run almost straight and parallel over the oceans, but there may be deviations and ups and downs when they run over the landmasses due to variations in climatic conditions over land.
3. Value of the isotherm goes on reducing from the equatorial to polar regions.
4. Lack of cloud cover allows insolation and radiation unhindered.

Question 14.
Why are cloudless nights cooler than the cloudy nights ?
Answer:
Cloud directly absorb 48% of sunlight in daytime which affect the insolation of the earth. Similarly when temperature of the earth is radiate in night time to balance the temperature on the surface of the earth, cloud prevents to radiate temperature. So that when the nights have cloud covered sky, these are warmer than the nights have clear sky or cloudless sky.

Question 15.
What do you mean by inversion of temperature?
Answer:
Generally temperature decreases with increasing height of the surface at a rate of 6.4°C per 1000 m. But in some exceptional cases, temperature is increase with increasing height of the surface. This phenomena is called inversion of temperature. In mountaineous regions, at night, there has been blown cold Katabetic wind from hill top to valley. As a result temperature on the hill top area are warmer than valley region.

Question 16.
Why the places of lower altitudes are warmer than the higher altitudes?
Answer:
Air density decreases with increasing height. In addition to this, amount of water vapour and dust particles are also decrease in higher altitudes. For these reasons, air is more warmer in low lying area and cooler in high.

Answer in details : 5 Marks

Question 1.
Explain the causes of difference in temperature in the atmosphere.
Answer:
The factors that cause difference in temperature in the atmosphere are :
(i) Latitude : The latitudes exercise the most dominant control over the duration of sunshine and thereby the length of the day. The higher is the latitude, the lower is the amount of heat received.

(ii) Altitude : By the normal lapse rate, temperature decreases by 6.4°C with every 1 km rise in altitude. Hence, higher altitude places are colder than lower regions.
(iii) Distribution of land and water bodies : Heat absorbing capacities of land and water bodies are not equal. Latent heat capacity of water is more compared to land. Hence, extremes of temperature are noticed on land, while water bodies show moderate range of temperature.
(iv) Wind : Hot winds blowing over cold areas tend to increase atmospheric temperature and vice versa.
(v) Ocean currents : Planetary winds influence ocean currents. Warm currents may be directed towards cold regions, thus increasing the temperature of the coastal regions, and vice versa.
(vi) Slope of land : In mountainous regions, one side receives more sunlight than the other. Hence, the slope that receives more sunlight is warmer than the opposite slope which is comparatively cooler.

(vii) Cloud cover : Cloud cover acts like an umbrella preventing escape of heat from the atmosphere, thus increasing temperature. Clear sky allows insolation and radiation at greater rates, thus resulting in large temperature differences between day and night.

(viii) Rainfall : Rainfall helps to reduce heat. Hence, heavy rainfall areas near the equator may appear to be less warm compared to less rainfall areas of tropical regions.
(ix) Vegetation : Dense vegetative cover stops solar energy to heat up the ground and also attract rainfall, hence influences the temperature conditions.
(x) Soil : Soils that can hold water, control temperature conditions as they do not get heated very fast. Dry and coarse soils get heated and cooled very fast.
(xi) Industrial and urban growth : Increase in number of industries, cars, cities and several urban activities tend to heat up the atmosphere more than rural areas.

Question 2.
Describe the temperature belts/zones of the earth in brief.
Answer:

The earth is divided into several temperature belts or zones according to the latitudes. They are : Torrid zone, North and South Temperate zones and North and South Frigid zone.

(i) Torrid zone: This lies from the Equator (0°) to the Tropic of Cancer ($$23^{1 / 2}$$° N) in the north and Tropic of Capricorn ($$23^{1 / 2}$$° S) in the south. The characteristics are:
(a) The sun gives vertical rays to this region.
(b) Length of day and night remains almost equal throughout the year.
(c) Average temperature is quite high (about 27°C )

(ii) North and South Temperate Zones : These zones spread from the Tropic of Cancer ($$23^{1 / 2}$$° N) to the Arctic Circle ($$66^{1 / 2}$$° N) in the north and from Tropic of Capricorn ($$23^{1 / 2}$$° S) to the Antarctic circle ($$66^{1 / 2}$$° S) in the south. The characteristics are :
(a) Sun gives medium inclined rays to this region.
(b) Average temperature is cooler than the Torrid zone.
(c) The $$23^{1 / 2}$$°-50° region is known as the warm temperate zone while the 50°-$$66^{1 / 2}$$° zone is known as the cool temperate zone.

(iii) North and South Frigid Zones : These zones spread from the Arctic Circle ($$66^{1 / 2}$$ ° N) to the North Pole (90° N) in the north and from the Antarctic Circle .($$66^{1 / 2}$$° S) to the South Pole (90° S) in the south. The characteristics are :
(a) The sun gives highly inclined rays to this region.
(b) Length of day and night is highly inequal.
(c) Average temperature remains below 0°C.
(d) Most of the time the region experiences snowfall and remains snow-covered.

Question 3.
What are the effects of global warming ?
Answer:
The effects of global warming are discussed below :
i. Melting of glaciers : Global warming increases the average temperature of the earth’s atmosphere, which results in melting of ice caps and glaciers. This will submerge coastal areas due to increase in level of sea water. The fluvial cycles will be disturbed and landforms will change. Many flora and fauna may be destroyed.

ii. Climatic change : The northern hemisphere will become hotter than the southern hemisphere due to presence of more land masses here. Amount of rainfall in Tropical regions will increase by 10-15%. The northern countries may experience flood and the southern countries will experience drought in the northern hemisphere.
Summers will be longer. Chances of thunder storms and cyclones will increase.

iii. Ecosystem : Change in climate due to global warming may result in extinction of many species of birds, animals and plants.

iv. Effect on vegetation and agriculture : Excessive heat may hamper the growth of coniferous trees in hilly areas. Mangroves may be drowned due to rise in sea water level. Some crops like corn, sugarcane, jowar, bajra etc. will have increased production while crops like rice, wheat, barley, soyabean, tobacco, jute etc. will reduce their growth.

v. Spread of diseases: The germs and bacteria will become highly active and spread diseases like dengue, malaria, yellow fever, encephalitis etc. Some tropical diseases may spread to higher latitudes also.

vi. Spread of deserts : High temperature and high rates of evaporation will turn many places arid and hence boost the spread of deserts.

vii. Forest fires : Too much heat will dry up leaves and branches and cause frequent forest fires.

Question 4.
What do you mean by green house gases? What are the uses of green house gases?
Answer:
The gases which play an important role in increasing the average temperature of the earth’s atmosphere are called Green House Gases. Some of the Green House Gases are Carbon Dioxide (CO2), Carbon Monoxide (CO), Methane (CH4), Chloro fluoro carbon (CFC), Nitrous Oxide (N2O), Water vapour, etc. Uses – The Green House Gases are prepared naturally in the environment and are also sometimes the outcome of human activities. These gases are very important for life activities. The sun’s energy reaches the earth’s surface daily as insolation, and is radiated back daily. The Green House Gases trap the outgoing infrared radiation and send it back towards the earth’s surface. This helps to keep the earth’s atmosphere warm, which would have otherwise become so chilled due to out-radiation that no life would have been possible on earth. But the problem is, if the amount of Green House Gases increases drastically, they will hold back so much heat that it will increase the atmospheric temperature at alarming rates. This condition will also be not suitable for existence of life on earth.