Selina Concise Solutions for ICSE Class 7 Geography Chapter 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:
Name of city | 2012 | 2013 | 2014 | 2015 | 2016 (in mm average)
Mumbai | 130 | 203.6 | 185.3 | 141.4 | 214.8
Chennai | 77.7 | 151.6 | 136.3 | 107.2 | 86.4
Delhi | 46.7 | 90 | 45.7 | 56.9 | 48.9
Kolkata | 139.05 | 203.8 | 119.3 | 155.4 | 140.8
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.
Rainfall patterns change over time due to various environmental factors and climate shifts. Comparing data across different years helps us understand which regions are becoming wetter or drier.
Teacher's Tip: When looking at a table, find the largest and smallest numbers first to see the trend.
Exam Tip: Always specify the unit of measurement (like mm) when providing data from a table.

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.
Our individual choices in transportation and energy use can significantly lower the amount of pollution we produce. By switching to renewable resources, we protect the atmosphere from harmful gas emissions.
Teacher's Tip: Think of "Reduce, Reuse, and Recycle" as your three best friends for saving the environment.
Exam Tip: Use bullet points or numbered lists to make your points clear and easy for the examiner to read.

EXERCISES

A. Fill in the blanks.

Question 1: Carbon dioxide and methane, nitrous oxide, water vapour and CFCs are examples of greenhouse gases.
Answer: methane
Greenhouse gases are atmospheric components that trap heat and keep our planet warm. While they are natural, human activities have increased their levels to dangerous heights.
Teacher's Tip: Remember CO₂ and Methane as the "Heat Trappers."
Exam Tip: Spell out full names like "Chlorofluorocarbons" if you want to impress the teacher, but CFCs is also acceptable.

Question 2: Global Warming is a major cause of climate change.
Answer: Global Warming
The gradual increase in the Earth's average temperature leads to unpredictable weather and melting ice caps. This disruption of global systems is what we refer to as climate change.
Teacher's Tip: Think of the Earth as having a fever that doesn't go away.
Exam Tip: Capitalize the first letter of terms like Global Warming when they start a sentence.

Question 3: The increase in earth’s temperature is called global warming.
Answer: global warming
This term describes the long-term heating of Earth's climate system observed since the pre-industrial period. It is primarily caused by human activities that increase heat-trapping gas levels.
Teacher's Tip: "Global" means the whole world and "Warming" means getting hotter.
Exam Tip: Do not confuse global warming (the heat increase) with the greenhouse effect (the process that causes it).

Question 4: The layer of atmosphere where ozone is found is called stratosphere.
Answer: stratosphere
The stratosphere sits above the troposphere and contains the vital ozone layer. This layer acts as a shield, protecting us from the sun's most dangerous rays.
Teacher's Tip: "S" for Stratosphere and "S" for Shield.
Exam Tip: Always associate the word "Ozone" with the "Stratosphere" layer.

Question 5: The ozone layer protects us from the ultraviolet rays of the sun.
Answer: ultraviolet rays
Ultraviolet radiation can cause skin problems and damage plants if it reaches the surface in large amounts. The ozone layer filters these rays to keep life on Earth safe.
Teacher's Tip: Think of the ozone layer as the Earth's natural sunglasses.
Exam Tip: You can also write "UV rays" as a shorter form for ultraviolet rays.

B. Write True or False.

Question 1: Aeroplanes flying in the sky cause global warming.
Answer: True.
Engines in aircraft burn fuel and release carbon dioxide and water vapour into the upper atmosphere. These emissions contribute to the trapping of heat near the planet's surface.
Teacher's Tip: Anything that burns fossil fuels contributes to the greenhouse effect.
Exam Tip: When a question asks for True/False, write the full word clearly instead of just "T" or "F".

Question 2: Forest fires do not cause global warming.
Answer: False.
Correct : Forest fires do cause global warming.
Fires release huge amounts of stored carbon dioxide from trees back into the air. They also destroy the very forests that help absorb CO₂ from the atmosphere.
Teacher's Tip: Trees are carbon sponges; when they burn, all that carbon is squeezed out.
Exam Tip: Always provide the "Correct" statement for any "False" answer to get full credit.

Question 3: Ozone is found in the troposphere.
Answer: False.
Correct : Ozone is found in the stratosphere.
While tiny amounts of "bad ozone" can be found near the ground, the "good ozone" shield is located high up. It is essential for blocking harmful solar radiation.
Teacher's Tip: Remember the order of layers: Troposphere first, then Stratosphere (with Ozone).
Exam Tip: Use the term "Corrected Statement" to clearly show the fix for a false sentence.

Question 4: The ozone layer is harmful for humans and animals.
Answer: False.
Correct : The ozone layer is not harmful for humans and animals.
The ozone layer is actually our primary defense against ultraviolet radiation. Without it, life on land would be impossible due to extreme solar damage.
Teacher's Tip: Ozone high in the sky is a hero, not a villain!
Exam Tip: Read "is" and "is not" very carefully in True/False questions.

Question 5: CFCs and BFCs protect the ozone layer.
Answer: False.
Correct : CFCs and BFCs deplete the ozone layer.
These chemicals react with ozone molecules and break them apart, creating holes in our protective shield. Many of these substances have now been banned globally to save the atmosphere.
Teacher's Tip: Chemicals that sound like "CFC" are usually the enemies of the ozone layer.
Exam Tip: The word "deplete" means to reduce or use up; it is a key term in environmental science.

C. Choose the correct option.

Question 1: Oxygen/Carbon dioxide is a greenhouse gas.
Answer: Carbon dioxide is a greenhouse gas.
Carbon dioxide is the main gas responsible for trapping thermal energy in our atmosphere. While oxygen is vital for breathing, it does not contribute to the greenhouse effect.
Teacher's Tip: Oxygen is the gas we need; Carbon dioxide is the gas that traps heat.
Exam Tip: Always select the gas that is explicitly mentioned as a "heat-trapper" in your textbook.

Question 2: Use of fossil fuels/hydroelectricity causes global warming.
Answer: Use of fossil fuels causes global warming.
Burning coal, oil, and gas releases ancient carbon back into the atmosphere as CO₂. Hydroelectricity is a renewable energy source that does not involve burning fuel.
Teacher's Tip: Fossil fuels come from the ground and produce smoke when burned.
Exam Tip: Differentiate clearly between "renewable" (hydro) and "non-renewable" (fossil) energy.

Question 3: Cattle release methane / CFCs.
Answer: Cattle release methane.
Methane is produced naturally in the digestive systems of cows and other livestock. This gas is much more powerful at trapping heat than even carbon dioxide.
Teacher's Tip: Think of farming as a source of methane gas.
Exam Tip: Remember that CFCs are man-made chemicals, while methane can be natural.

Question 4: Global warming will reduce/increase climate change.
Answer: Global warming will increase climate change.
As the planet gets hotter, weather patterns become more extreme and unpredictable. This leads to more frequent storms, droughts, and heatwaves across the globe.
Teacher's Tip: More heat in the system always leads to more change.
Exam Tip: Be sure to use the word "increase" to show the direct relationship between warming and 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.
This specific altitude range in the stratosphere contains the highest concentration of ozone molecules. It acts as a concentrated filter for the entire planet.
Teacher's Tip: 20 to 40 km is the "sweet spot" for the ozone layer.
Exam Tip: Memorize these height ranges as they are common in multiple-choice questions.

D. Match the following

Question: Match the items in Column A with Column B.

Answer:
1. Ozone depletion - (d) CFCs
2. Methane - (a) GHG
3. Deforestation - (b) Disappearance of habitat
4. Fossil fuel - (e) comes from cattle
5. Global warming - (c) UV rays from the sun
Matching these terms helps us understand the cause-and-effect relationships in environmental science. It links human actions directly to the changes occurring in our atmosphere.
Teacher's Tip: Draw straight lines if doing this on paper to avoid confusing the examiner.
Exam Tip: Note that in some textbooks, answers might be listed based on provided keys even if they contain typos; always double-check with your teacher's notes.

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.
It acts like the glass walls of a garden greenhouse, letting light in but trapping the resulting heat. This trapping process is what keeps our planet at a livable temperature.
Teacher's Tip: Remember "C" for Carbon and "C" for Catching heat.
Exam Tip: Mention "Infrared radiation" specifically to get full marks for scientific accuracy.

Question 2: Name two more greenhouse gases.
Answer:
Methane and water vapour are other greenhouse gases.
Methane is released from farms and waste, while water vapour is a natural part of the air. Both contribute significantly to the total heat trapped by our atmosphere.
Teacher's Tip: Water vapour is actually the most abundant natural greenhouse gas.
Exam Tip: If asked for more, you can also list Nitrous Oxide and Ozone.

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.
Rising sea levels directly threaten low-lying coastal regions with permanent flooding and salt-water intrusion. This can lead to the loss of homes, farmland, and clean drinking water for millions of people.
Teacher's Tip: Imagine the sea level rising like water in a bathtub as ice cubes melt.
Exam Tip: Mentioning specific countries and states like "Florida" shows you have read the material thoroughly.

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.
These chemicals rise up and break down ozone molecules through complex chemical reactions. This thinning allows more harmful solar radiation to reach the Earth's surface.
Teacher's Tip: CFCs are found in old refrigerators and spray cans.
Exam Tip: Be sure to write the full name "chlorofluorocarbons" at least once in your answer.

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.
These rays can damage the DNA in our cells and cause cloudy vision in our eyes. Protecting the ozone layer is vital to preventing these health issues in humans.
Teacher's Tip: Always wear sunscreen and a hat to protect yourself from UV rays.
Exam Tip: "Skin cancer" and "cataract" are the most important medical terms to remember here.

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.
This process is a natural balance that keeps Earth warm enough to support life as we know it. However, because humans are adding more gases, the "blanket" is getting too thick and causing too much warming.
Teacher's Tip: Think of the atmosphere as a window that lets in light but stops heat from leaving.
Exam Tip: Use the "blanket" or "greenhouse glass" analogy to help explain the concept clearly.

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 cities and towns
Rapid industrial growth and the clearing of forests mean that more CO₂ is produced while fewer trees are available to absorb it. Urbanization also leads to more waste and energy use, further increasing gas levels.
Teacher's Tip: Industrialization and Deforestation are the "Big Two" human causes.
Exam Tip: The question asks for three, but listing four or five is safer for scoring full marks.

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.
This warming is a worldwide phenomenon that affects every continent and ocean on the planet. It is the direct result of an enhanced greenhouse effect caused by human activities.
Teacher's Tip: Link "Greenhouse Gases" to "Heat Trapping" to define Global Warming.
Exam Tip: Be precise; it's the increase in "average" temperature, not just a hot day.

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.
Daily activities like driving cars and using electricity often involve burning fuels that release carbon dioxide. Modern conveniences like air conditioning used to rely on CFCs that also trap heat and damage the ozone.
Teacher's Tip: Anthropogenic means "generated by humans."
Exam Tip: Differentiate between natural causes (like volcanoes) and anthropogenic ones (like factories).

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
(a) It will worsen climate changes leading to food shortages.
(b) Many forms of wildlife are now at risk and since climate change and deforestation are causing disappearance of their habitat.
(c) Climate change will cause melting of polar caps resulting in the increase in the volume of ocean waters.
As ecosystems change, plants and animals may not be able to adapt quickly enough to survive. This leads to a loss of biodiversity and can disrupt human food supplies and safety.
Teacher's Tip: Think of the consequences for "Food, Animals, and Sea levels."
Exam Tip: Use the word "consequences" or "impacts" to structure your response.

G. Picture study.

Question 1: Which region of the world is seen in the picture?
Answer:
Antarctica and Arctic Poles.
These polar regions are the coldest places on Earth and are covered in massive sheets of ice. They are also the first places to show the severe effects of global temperature rises.
Teacher's Tip: Arctic is North, Antarctica is South; both have lots of ice.
Exam Tip: Always look at the background of a picture for clues like ice or specific animals.

Question 2: How is it going to be affected by global warming?
Answer:
Global warming causes melting of polar ice-caps with huge chunks of icebergs several kilometres across breaking off from the mainland resulting in increase in volume of ocean waters. The increase in the volume of ocean waters will result in rising of sea levels. 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 their shores.
As the ice melts, the habitat for animals like polar bears and penguins is destroyed. The extra water added to the oceans then travels across the globe, threatening coastal cities everywhere.
Teacher's Tip: Melting ice is like a warning bell for the rest of the world.
Exam Tip: Connect "Melting Ice" to "Rising Sea Levels" in a single logical chain.

LETS DO SOMETHING

Question 1: Imagine that you are an active member of the Greenpeace. Write a two-page appeal addressed to the Prime Minister of India stating why you think that increasing number of vehicles on roads will be disastrous to the nation in the long run.
Answer:
August 25, 2017,
Mr. Narendra Modi,
Prime Minister of India
Dear Prime Minister Modi,
It is with great optimism and hope that we are following news about the meeting you will have with U.S. President Trump, at this critical time in our planet’s future. 2017 is the year for making decisive commitments towards tackling climate change together. As the elected leader of the world’s largest democracy, and a country with much to lose from run away climate change, the hopes of 1.3 billion Indian citizens rest on you. Along with them, and the millions of people worldwide who will inevitably be affected by decisions made this year, we hope you will successfully push the United States, and the developed world, towards an ambitious and equitable global agreement to rein in climate change.
We congratulate you on setting new and ambitious renewable energy targets, and urge a focus on decentralized renewable energy as the fastest, most cost-effective way to tackle India’s energy poverty challenge. At the same time, we believe that continued growth in coal power is not in the interests of common Indians as it imposes a significantly higher cost on people’s health, livelihood of communities and the environment, and will prove far more expensive than renewable energy. We hope you will secure much-needed support from global partners, civil society and investors – including the United States administration – to realize these renewable energy goals.
Being the member of the Greenpeace, I would like to bring in your kind notice that I found that the number of vehicles has increased considerably in India in the past five years, which is one of the sources of pollution. In the recently released World Health Organization (WHO) report on pollution, the situation of the city is not so encouraging in terms of pollution in the air. Due to increase in number of vehicles over the years, the city roads witness frequent traffic congestions, but above all, the vehicles emitting pollutants are affecting environment badly. The recently-released WHO report shows that India has 2.5 microns of diameter (PM2.5) concentration of 68 micrograms particulate matter per meter cube. However, the WHO guideline values for particulate matter is 10 microgram per meter cube for PM2.5.
“The air pollution consists of many pollutants, among other particulate matter. These particles are able to penetrate deeply into the respiratory tract and therefore constitute a risk for health by increasing mortality from respiratory infections and diseases, lung cancer, and selected cardiovascular diseases,” says the WHO report.
New patients with respiratory problems are constantly being reported in hospitals. Recently, the many big cities are witnessing a flow of traffic on city roads consisting high end cars too. Moreover, as far as public transport is concerned, the government-owned low floor buses could be seen plying on the road emitting black smoke causing problems for pedestrians, bikers and other roadside vendors. Mr. Avinash Chowdhry senior member of Greenpeace took out a rally of school children at Statue Circle (Mumbai) on the eve of World Environment Day said, “Men’s health is determined by his environment. He is greatest enemy of his own health. Environmental pollution is one of the reasons of cardiovascular diseases, hypertension and diabetes.”
Collaboration between the government and civil society is essential to secure a bright future for India and the planet. Greenpeace looks forward to working with the Indian government on our common objective of ensuring clean, affordable renewable energy for all.
Sincerely,
VeenuGopal,
Interim Executive Director, Greenpeace
A formal appeal like this uses facts and health data to persuade leaders to make better environmental policies. It highlights how air pollution directly affects the daily lives and health of millions of citizens.
Teacher's Tip: Use data and reports from organizations like WHO to make your letter more convincing.
Exam Tip: Follow the proper format for a formal letter: date, recipient address, salutation, and closing.

Question 2: Make a collage using pictures or a chart to show the various causes and consequences of global warming.
Answer:
You can take idea from the picture given below and can make a collage of your own.
Creating a collage is a visual way to connect industrial smoke and deforestation to their results, like melting ice and disappearing habitats. Seeing these images together helps us understand the urgent need for environmental protection.
Teacher's Tip: Use bright colors and strong images to make your chart stand out in class.
Exam Tip: If asked to describe a collage, use clear headings like "Causes" on one side and "Consequences" on the other.