Selina Textbook Solutions: Greenhouse Effect and Global Warming | Geography Class 7 ICSE PDF Download

 Page 1


Greenhouse Effect and Global Warming 
DISCUSS 
Collect rainfall data from the website of Indian Meteorological Department (IMD) for 
Mumbai, Chennai, Delhi and Kolkata and discuss how rainfall patterns have changed in 
the last 5 years. 
Answer: 
 
Mumbai receives maximum rainfall in 2016 and minimum rainfall in 2012. 
Chennai receives maximum rainfall in 2013 and minimum rainfall in 2012. 
Delhi receives maximum rainfall in 2013 and minimum rainfall in 2014. 
Kolkata receives maximum rainfall in 2013 and minimum rainfall in 2014. 
VALUES AND LIFE SKILLS : 
We need to understand that global warming, climate change, acid rain and ozone 
depletion are all happening because of our dependence on fossil fuels and CFC-based 
technologies. Therefore, the need of the hour is to reduce 
our dependence on them. 
What can you do in this regard ? 
Answer: 
The ways to reduce our dependency on them are : 
1. By using materials such as bamboo, recycled metal and organic paints in 
construction of buildings. 
2. By using solar energy to heat and light homes and offices. 
3. By using clean fuel like CNG and unleaded petrol to run vehicles. 
4. By making changes in everyday practices such as 
(a) choosing to travel in public vehicles, biking, walking or using a car pool. 
(b) buying energy efficient household appliances. 
(c) replacing light bulbs with CFL bulbs. 
 
Page 2


Greenhouse Effect and Global Warming 
DISCUSS 
Collect rainfall data from the website of Indian Meteorological Department (IMD) for 
Mumbai, Chennai, Delhi and Kolkata and discuss how rainfall patterns have changed in 
the last 5 years. 
Answer: 
 
Mumbai receives maximum rainfall in 2016 and minimum rainfall in 2012. 
Chennai receives maximum rainfall in 2013 and minimum rainfall in 2012. 
Delhi receives maximum rainfall in 2013 and minimum rainfall in 2014. 
Kolkata receives maximum rainfall in 2013 and minimum rainfall in 2014. 
VALUES AND LIFE SKILLS : 
We need to understand that global warming, climate change, acid rain and ozone 
depletion are all happening because of our dependence on fossil fuels and CFC-based 
technologies. Therefore, the need of the hour is to reduce 
our dependence on them. 
What can you do in this regard ? 
Answer: 
The ways to reduce our dependency on them are : 
1. By using materials such as bamboo, recycled metal and organic paints in 
construction of buildings. 
2. By using solar energy to heat and light homes and offices. 
3. By using clean fuel like CNG and unleaded petrol to run vehicles. 
4. By making changes in everyday practices such as 
(a) choosing to travel in public vehicles, biking, walking or using a car pool. 
(b) buying energy efficient household appliances. 
(c) replacing light bulbs with CFL bulbs. 
 
EXERCISES 
A. Fill in the blanks. 
1. Carbon dioxide and methane, nitrous oxide, water vapour and CFCs are 
examples of greenhouse gases. 
2. Global Warming is a major cause of climate change. 
3. The increase in earth’s temperature is called global warming. 
4. The layer of atmosphere where ozone is found is called stratosphere. 
5. The ozone layer protects us from the ultraviolet rays of the sun. 
B. Write True or False. 
1. Aeroplanes flying in the sky cause global warming. 
Answer. True. 
2. Forest fires do not cause global warming. 
Answer. False. 
Correct : Forest fires do cause global warming. 
3. Ozone is found in the troposphere. 
Answer. False. 
Correct : Ozone is found in the stratosphere. 
4. The ozone layer is harmful for humans and animals. 
Answer. False. 
Correct : The ozone layer is not harmful for humans and animals. 
5. CFCs and BFCs protect the ozone layer. 
Answer. False. 
Correct : CFCs and BFCs deplete the ozone layer. 
C. Choose the correct option. 
Question 1. 
Oxygen/Carbon dioxide is a greenhouse gas. 
Answer: 
Carbon dioxide is a greenhouse gas. 
 
Page 3


Greenhouse Effect and Global Warming 
DISCUSS 
Collect rainfall data from the website of Indian Meteorological Department (IMD) for 
Mumbai, Chennai, Delhi and Kolkata and discuss how rainfall patterns have changed in 
the last 5 years. 
Answer: 
 
Mumbai receives maximum rainfall in 2016 and minimum rainfall in 2012. 
Chennai receives maximum rainfall in 2013 and minimum rainfall in 2012. 
Delhi receives maximum rainfall in 2013 and minimum rainfall in 2014. 
Kolkata receives maximum rainfall in 2013 and minimum rainfall in 2014. 
VALUES AND LIFE SKILLS : 
We need to understand that global warming, climate change, acid rain and ozone 
depletion are all happening because of our dependence on fossil fuels and CFC-based 
technologies. Therefore, the need of the hour is to reduce 
our dependence on them. 
What can you do in this regard ? 
Answer: 
The ways to reduce our dependency on them are : 
1. By using materials such as bamboo, recycled metal and organic paints in 
construction of buildings. 
2. By using solar energy to heat and light homes and offices. 
3. By using clean fuel like CNG and unleaded petrol to run vehicles. 
4. By making changes in everyday practices such as 
(a) choosing to travel in public vehicles, biking, walking or using a car pool. 
(b) buying energy efficient household appliances. 
(c) replacing light bulbs with CFL bulbs. 
 
EXERCISES 
A. Fill in the blanks. 
1. Carbon dioxide and methane, nitrous oxide, water vapour and CFCs are 
examples of greenhouse gases. 
2. Global Warming is a major cause of climate change. 
3. The increase in earth’s temperature is called global warming. 
4. The layer of atmosphere where ozone is found is called stratosphere. 
5. The ozone layer protects us from the ultraviolet rays of the sun. 
B. Write True or False. 
1. Aeroplanes flying in the sky cause global warming. 
Answer. True. 
2. Forest fires do not cause global warming. 
Answer. False. 
Correct : Forest fires do cause global warming. 
3. Ozone is found in the troposphere. 
Answer. False. 
Correct : Ozone is found in the stratosphere. 
4. The ozone layer is harmful for humans and animals. 
Answer. False. 
Correct : The ozone layer is not harmful for humans and animals. 
5. CFCs and BFCs protect the ozone layer. 
Answer. False. 
Correct : CFCs and BFCs deplete the ozone layer. 
C. Choose the correct option. 
Question 1. 
Oxygen/Carbon dioxide is a greenhouse gas. 
Answer: 
Carbon dioxide is a greenhouse gas. 
 
Question 2. 
Use of fossil fuels/hydroelectricity causes global warming. 
Answer: 
Use of fossil fuels causes global warming. 
Question 3. 
Cattle release methane / CFCs. 
Answer: 
Cattle release methane. 
Question 4. 
Global warming will reduce/increase climate change. 
Answer: 
Global warming will increase climate change. 
Question 5. 
The ozone layer is found between 20 and 40/40 and 60 km above the earth’s surface. 
Answer: 
The ozone layer is found between 20 and 40 and above the earth’s surface. 
D. Match the following 
 
Answer: 
 
 
 
Page 4


Greenhouse Effect and Global Warming 
DISCUSS 
Collect rainfall data from the website of Indian Meteorological Department (IMD) for 
Mumbai, Chennai, Delhi and Kolkata and discuss how rainfall patterns have changed in 
the last 5 years. 
Answer: 
 
Mumbai receives maximum rainfall in 2016 and minimum rainfall in 2012. 
Chennai receives maximum rainfall in 2013 and minimum rainfall in 2012. 
Delhi receives maximum rainfall in 2013 and minimum rainfall in 2014. 
Kolkata receives maximum rainfall in 2013 and minimum rainfall in 2014. 
VALUES AND LIFE SKILLS : 
We need to understand that global warming, climate change, acid rain and ozone 
depletion are all happening because of our dependence on fossil fuels and CFC-based 
technologies. Therefore, the need of the hour is to reduce 
our dependence on them. 
What can you do in this regard ? 
Answer: 
The ways to reduce our dependency on them are : 
1. By using materials such as bamboo, recycled metal and organic paints in 
construction of buildings. 
2. By using solar energy to heat and light homes and offices. 
3. By using clean fuel like CNG and unleaded petrol to run vehicles. 
4. By making changes in everyday practices such as 
(a) choosing to travel in public vehicles, biking, walking or using a car pool. 
(b) buying energy efficient household appliances. 
(c) replacing light bulbs with CFL bulbs. 
 
EXERCISES 
A. Fill in the blanks. 
1. Carbon dioxide and methane, nitrous oxide, water vapour and CFCs are 
examples of greenhouse gases. 
2. Global Warming is a major cause of climate change. 
3. The increase in earth’s temperature is called global warming. 
4. The layer of atmosphere where ozone is found is called stratosphere. 
5. The ozone layer protects us from the ultraviolet rays of the sun. 
B. Write True or False. 
1. Aeroplanes flying in the sky cause global warming. 
Answer. True. 
2. Forest fires do not cause global warming. 
Answer. False. 
Correct : Forest fires do cause global warming. 
3. Ozone is found in the troposphere. 
Answer. False. 
Correct : Ozone is found in the stratosphere. 
4. The ozone layer is harmful for humans and animals. 
Answer. False. 
Correct : The ozone layer is not harmful for humans and animals. 
5. CFCs and BFCs protect the ozone layer. 
Answer. False. 
Correct : CFCs and BFCs deplete the ozone layer. 
C. Choose the correct option. 
Question 1. 
Oxygen/Carbon dioxide is a greenhouse gas. 
Answer: 
Carbon dioxide is a greenhouse gas. 
 
Question 2. 
Use of fossil fuels/hydroelectricity causes global warming. 
Answer: 
Use of fossil fuels causes global warming. 
Question 3. 
Cattle release methane / CFCs. 
Answer: 
Cattle release methane. 
Question 4. 
Global warming will reduce/increase climate change. 
Answer: 
Global warming will increase climate change. 
Question 5. 
The ozone layer is found between 20 and 40/40 and 60 km above the earth’s surface. 
Answer: 
The ozone layer is found between 20 and 40 and above the earth’s surface. 
D. Match the following 
 
Answer: 
 
 
 
E. Answer the following questions in brief  
Question 1. 
Why do we call carbon dioxide a greenhouse gas? 
Answer: 
Carbon dioxide is called greenhouse gas because it absorbs 
Infrared radiations. A greenhouse gas is a gas in an atmosphere that absorbs and emits 
radiation within the thermal infrared range. 
Question 2. 
Name two more greenhouse gases. 
Answer: 
Methane and water vapour are other greenhouse gases. 
Question 3. 
How will countries like Bangladesh and Thailand be affected by global warming? 
Answer: 
Climate change will cause melting of polar ice caps with huge chunks of icebergs 
several kilometres across breaking off from the mainland. This is already taking place 
around the Arctic and in Antarctica. The result will be an increase in the volume of 
ocean waters. Countries like Bangladesh, Thailand and Malaysia and the Southeastern 
parts of USA like the States of Florida and Louisiana would be swamped by flood water 
along its shores. 
Question 4. 
What is responsible for causing a hole in the ozone layer? 
Answer: 
The release of large amount of CFCs or chlorofluorocarbons and BFCs or 
bromofluorocarbons by industries are responsible for the formation of holes in the ozone 
layer. 
Question 5. 
Name some diseases that are caused due to exposure to ultraviolet rays of the sun. 
Answer: 
Exposure to UV rays can cause sunburn, cataract, hair loss, skin cancer and birth 
deformities. 
F. Answer the following questions in one or two paragraphs  
Question 1. 
How is the greenhouse effect created? 
Answer: 
The ‘greenhouse effect’ takes place when the ‘sun’s rays heat the earth. This heat is 
absorbed by the surface of the earth and some of it is radiated back into the 
Page 5


Greenhouse Effect and Global Warming 
DISCUSS 
Collect rainfall data from the website of Indian Meteorological Department (IMD) for 
Mumbai, Chennai, Delhi and Kolkata and discuss how rainfall patterns have changed in 
the last 5 years. 
Answer: 
 
Mumbai receives maximum rainfall in 2016 and minimum rainfall in 2012. 
Chennai receives maximum rainfall in 2013 and minimum rainfall in 2012. 
Delhi receives maximum rainfall in 2013 and minimum rainfall in 2014. 
Kolkata receives maximum rainfall in 2013 and minimum rainfall in 2014. 
VALUES AND LIFE SKILLS : 
We need to understand that global warming, climate change, acid rain and ozone 
depletion are all happening because of our dependence on fossil fuels and CFC-based 
technologies. Therefore, the need of the hour is to reduce 
our dependence on them. 
What can you do in this regard ? 
Answer: 
The ways to reduce our dependency on them are : 
1. By using materials such as bamboo, recycled metal and organic paints in 
construction of buildings. 
2. By using solar energy to heat and light homes and offices. 
3. By using clean fuel like CNG and unleaded petrol to run vehicles. 
4. By making changes in everyday practices such as 
(a) choosing to travel in public vehicles, biking, walking or using a car pool. 
(b) buying energy efficient household appliances. 
(c) replacing light bulbs with CFL bulbs. 
 
EXERCISES 
A. Fill in the blanks. 
1. Carbon dioxide and methane, nitrous oxide, water vapour and CFCs are 
examples of greenhouse gases. 
2. Global Warming is a major cause of climate change. 
3. The increase in earth’s temperature is called global warming. 
4. The layer of atmosphere where ozone is found is called stratosphere. 
5. The ozone layer protects us from the ultraviolet rays of the sun. 
B. Write True or False. 
1. Aeroplanes flying in the sky cause global warming. 
Answer. True. 
2. Forest fires do not cause global warming. 
Answer. False. 
Correct : Forest fires do cause global warming. 
3. Ozone is found in the troposphere. 
Answer. False. 
Correct : Ozone is found in the stratosphere. 
4. The ozone layer is harmful for humans and animals. 
Answer. False. 
Correct : The ozone layer is not harmful for humans and animals. 
5. CFCs and BFCs protect the ozone layer. 
Answer. False. 
Correct : CFCs and BFCs deplete the ozone layer. 
C. Choose the correct option. 
Question 1. 
Oxygen/Carbon dioxide is a greenhouse gas. 
Answer: 
Carbon dioxide is a greenhouse gas. 
 
Question 2. 
Use of fossil fuels/hydroelectricity causes global warming. 
Answer: 
Use of fossil fuels causes global warming. 
Question 3. 
Cattle release methane / CFCs. 
Answer: 
Cattle release methane. 
Question 4. 
Global warming will reduce/increase climate change. 
Answer: 
Global warming will increase climate change. 
Question 5. 
The ozone layer is found between 20 and 40/40 and 60 km above the earth’s surface. 
Answer: 
The ozone layer is found between 20 and 40 and above the earth’s surface. 
D. Match the following 
 
Answer: 
 
 
 
E. Answer the following questions in brief  
Question 1. 
Why do we call carbon dioxide a greenhouse gas? 
Answer: 
Carbon dioxide is called greenhouse gas because it absorbs 
Infrared radiations. A greenhouse gas is a gas in an atmosphere that absorbs and emits 
radiation within the thermal infrared range. 
Question 2. 
Name two more greenhouse gases. 
Answer: 
Methane and water vapour are other greenhouse gases. 
Question 3. 
How will countries like Bangladesh and Thailand be affected by global warming? 
Answer: 
Climate change will cause melting of polar ice caps with huge chunks of icebergs 
several kilometres across breaking off from the mainland. This is already taking place 
around the Arctic and in Antarctica. The result will be an increase in the volume of 
ocean waters. Countries like Bangladesh, Thailand and Malaysia and the Southeastern 
parts of USA like the States of Florida and Louisiana would be swamped by flood water 
along its shores. 
Question 4. 
What is responsible for causing a hole in the ozone layer? 
Answer: 
The release of large amount of CFCs or chlorofluorocarbons and BFCs or 
bromofluorocarbons by industries are responsible for the formation of holes in the ozone 
layer. 
Question 5. 
Name some diseases that are caused due to exposure to ultraviolet rays of the sun. 
Answer: 
Exposure to UV rays can cause sunburn, cataract, hair loss, skin cancer and birth 
deformities. 
F. Answer the following questions in one or two paragraphs  
Question 1. 
How is the greenhouse effect created? 
Answer: 
The ‘greenhouse effect’ takes place when the ‘sun’s rays heat the earth. This heat is 
absorbed by the surface of the earth and some of it is radiated back into the 
atmosphere. However, a part of this heat is trapped in the atmosphere by gases such 
as water vapour, carbon dioxide and methane while the rest escapes into space. These 
gases let in light from the sun but prevent the heat from escaping like the glass walls of 
a greenhouse. They also act like a mirror and reflect back to the earth some of the 
trapped heat energy. The more greenhouse gases (GHGs) are present in the 
atmosphere, the more heat is trapped, subsequently making the earth warmer. 
Question 2. 
State three causes that have led to an increase in greenhouse gases in the 
atmosphere. 
Answer: 
The causes that have led to the increase in greenhouse gases (GHGs) are: 
1. Increase in industries 
2. Increase in deforestation 
3. Increase in atmospheric pollution due to emissions from chimneys of factories 
4. Increase in natural disasters like floods, volcanic eruptions and earthquakes that 
release large amounts of smoke, dust and gases into the atmosphere 
5. Increase in the methane content of the atmosphere because of large-scale cattle 
rearing, since cattle release methane 
6. Expansion of cies and towns 
Question 3. 
What do you understand by the term ‘global warming’? 
Answer: 
The greenhouse gases in the atmosphere trap a part of the heat radiated back by the 
earth, increasing its temperature. The increase in the earth’s temperature is called 
global warming. 
Question 4. 
State some anthropogenic (man-made) causes of global warming. 
Answer: 
Man-made causes of global warming ‘include burning of fossil fuels, cutting of forests, 
using refrigerators, air conditioners, aerosols, factories belching smoke, increase in 
methane content of the atmosphere because of large-scale cattle rearing, expansion of 
cities and towns. 
Question 5. 
Global warming does not augur well for our planet earth. State at least three reasons to 
support this statement. 
Answer: 
Global warming is not good for our planet as