Chapter 3 – Atmosphere and Climate - Class 9 Social Science

2 MARKS

Q1. A mountain climber feels that the air becomes thinner as he climbs higher. Why does this happen?

Answer: Atmospheric pressure and air density decrease with increasing altitude because there are fewer air molecules above the person.

Q2. A pilot is flying at a high altitude and experiences very low temperature. Why does temperature generally decrease with altitude in the troposphere?

Answer: The troposphere is heated mainly from the Earth's surface. As altitude increases, the distance from the heated surface increases, so temperature generally decreases.

Q3. A student says, “Weather and climate are the same thing.” Is the statement correct? Give one difference.

Answer: No. Weather refers to atmospheric conditions over a short period, whereas climate refers to the average pattern of weather over a long period.

Q4. Why is the stratosphere important for life on Earth?

Answer: The ozone layer in the stratosphere absorbs much of the Sun's harmful ultraviolet radiation and protects living organisms.

Q5. Why does the south-west monsoon bring rainfall to most parts of India?

Answer: During summer, land heats faster than the surrounding sea, creating low pressure over land. Moist winds blow from the high-pressure ocean towards the low-pressure land, bringing rainfall.

Q6. Why does Tamil Nadu receive important rainfall during the north-east monsoon?

Answer: The north-east monsoon winds pass over the Bay of Bengal, absorb moisture and bring rainfall to the south-eastern coast, especially Tamil Nadu.

Q7. A farmer is worried about a weak monsoon. Why can a weak monsoon affect agricultural production?

Answer: Much of India's agriculture depends on monsoon rainfall. A weak monsoon can reduce water availability and cause drought-like conditions, affecting crop production.

Q8. How can deforestation contribute to climate change?

Answer: Trees absorb carbon dioxide. Deforestation reduces this carbon absorption and also releases stored carbon, increasing greenhouse gases in the atmosphere.

Q9. A family frequently uses private cars, wastes electricity and uses disposable plastics. What does this indicate about its carbon footprint?

Answer: These activities generally increase the family's carbon footprint because they contribute to greenhouse-gas emissions through transport, energy use and consumption patterns.

Q10. In the 2025 Punjab floods, houses and farms were built close to rivers. How could this have increased flood damage?

Answer: Construction close to rivers reduced the natural space available for floodwater to spread safely, increasing the damage to houses, farms and infrastructure.

3 MARKS

Q1. A weather report says that Kolkata will experience heavy rain tomorrow, while a climate report describes Kolkata's general rainfall pattern over many years. Differentiate between the two.

Answer:

• Weather: Short-term atmospheric conditions, such as tomorrow's rainfall.
• Climate: Long-term average pattern of temperature, rainfall and other atmospheric conditions.
• Weather can change from day to day, while climate describes longer-term patterns.

Q2. Explain why the atmosphere is essential for life on Earth.

Answer: The atmosphere:

1. Provides essential gases such as oxygen and nitrogen.
2. Contains water vapour and helps in the formation of clouds and rainfall.
3. Helps regulate temperature and protects life from harmful radiation.

Q3. A passenger travelling from sea level to a high mountain notices changes in temperature and air pressure. Explain why.

Answer:

• Atmospheric pressure decreases as altitude increases.
• Air becomes less dense at higher elevations.
• In the troposphere, temperature generally decreases with increasing altitude.

Q4. Explain how unequal heating of land and sea causes the south-west monsoon.

Answer:

1. During summer, India's landmass heats faster than the surrounding oceans.
2. Low pressure develops over the heated land, while relatively higher pressure remains over the ocean.
3. Moist winds move from the ocean towards land, producing the south-west monsoon and widespread rainfall.

Q5. Why is the monsoon important for India's economy and people's lives?

Answer:

• Agriculture depends heavily on monsoon rainfall.
• Good rainfall supports water supplies in rivers, reservoirs and wells.
• Monsoon affects transport, employment, daily life and rural livelihoods.
• Excessive rainfall may cause floods, while weak rainfall can cause droughts.

Q6. A farmer wants to use traditional knowledge to predict seasonal rainfall. Name two Indian sources mentioned in the chapter and explain their relevance.

Answer:

• Kṛiṣhiparāśhara describes methods of predicting rainfall based partly on the positions of the Moon and Sun.
• Bṛihatsaṁhitā describes rainfall prediction using lunar mansions or nakṣhatras.
• These traditions show India's long history of observing and studying seasonal weather.

Q7. Explain three major human causes of climate change.

Answer:

1. Burning fossil fuels releases carbon dioxide.
2. Deforestation reduces carbon absorption and can release stored carbon.
3. Industrial pollution releases greenhouse gases.

These increase greenhouse-gas concentrations and contribute to global warming.

Q8. A student wants to reduce his carbon footprint. Suggest three practical changes based on the chapter.

Answer: The student can:

1. Walk, cycle or use public transport instead of unnecessary private-car travel.
2. Switch off electrical appliances when not required.
3. Reuse and recycle materials and avoid single-use plastics.

These actions can reduce greenhouse-gas emissions.

Q9. The 2025 Punjab floods were caused by both natural and human factors. Give one example of each and explain their contribution.

Answer:

• Natural factor: Very heavy monsoon rainfall and swelling of major rivers caused rivers to overflow.
• Human factor: Weak river embankments, construction near rivers and poor warning systems increased the damage.
• Therefore, natural hazards can become more destructive when human planning and preparedness are inadequate.

Q10. Why can two Indian cities at similar latitudes have different climates?

Answer: Climate depends on several factors besides latitude, including:

• Altitude
• Distance from the sea
• Relief/topography
• Wind and monsoon patterns
• Other geographical conditions

Therefore, places at similar latitudes may still experience different temperatures and rainfall.

5 MARKS

Q1. A student is asked to explain the structure of the atmosphere to a group of younger students. Explain the major layers and their significance.

Answer: The atmosphere has five major layers:

1. Troposphere – The lowest layer; contains most of the atmosphere's water vapour and dust. Most weather phenomena occur here.
2. Stratosphere – Contains the ozone layer, which protects life from harmful ultraviolet radiation.
3. Mesosphere – A very cold layer where many meteors burn up.
4. Thermosphere – Temperatures are very high; it includes the ionosphere, which is important for radio communication.
5. Exosphere – The outermost layer, gradually merging into outer space.

Thus, each layer has distinct characteristics and contributes to Earth's environment.

Q2. Explain the complete mechanism of the south-west monsoon in India.

Answer:

1. During summer, the Indian landmass heats faster than the surrounding ocean.
2. This creates a low-pressure area over the Indian subcontinent.
3. The Indian Ocean remains relatively cooler and develops comparatively higher pressure.
4. Winds move from high-pressure areas towards low-pressure areas.
5. Moist winds blow from the Indian Ocean, Arabian Sea and Bay of Bengal towards India.
6. These winds bring widespread rainfall between June and September.

Therefore, the unequal heating of land and sea is a major factor behind the south-west monsoon.

Q3. Compare the south-west monsoon and north-east monsoon.

Answer:

South-West Monsoon	North-East Monsoon
Mainly occurs June–September	Mainly occurs October–February
Also called summer monsoon	Also called winter monsoon
Winds generally blow from sea to land	Winds generally blow from land to sea
Brings most of India's annual rainfall	Generally dry for much of India
Important for agriculture across much of India	Brings important rainfall to south-eastern India

The north-east monsoon picks up moisture over the Bay of Bengal, bringing rainfall particularly to Tamil Nadu and nearby regions.

Q4. Study the following data from the chapter:

• Shillong – Annual rainfall: 225.3 cm
• Kolkata – Annual rainfall: 162.5 cm
• Delhi – Annual rainfall: 67.0 cm
• Jodhpur – Annual rainfall: 36.6 cm

What does this data tell you about India's climate? Give reasons for the differences.

Answer: The data shows that rainfall varies greatly across India.

• Shillong receives very high rainfall because of its location and relief, which favour the uplift of moist monsoon winds.
• Kolkata receives substantial monsoon rainfall because of its location in eastern India.
• Delhi receives considerably less rainfall as it lies farther from the main sources of moisture.
• Jodhpur receives very little rainfall because it is located in the dry north-western region.

Thus, India's climate is highly diverse, influenced by location, relief, distance from the sea and monsoon winds.

Q5. A city experiences increasing temperatures, irregular rainfall, floods and periods of drought. Explain how climate change can produce such changes and suggest measures to address it.

Answer: Climate change refers to long-term changes in weather patterns, including temperature and rainfall.

Causes:

• Burning fossil fuels
• Deforestation
• Industrial pollution
• Increased greenhouse gases

Effects:

• Rising temperatures
• More frequent floods and droughts
• Melting glaciers
• Rising sea levels
• Loss of biodiversity
• Impacts on agriculture and health

Measures:

• Reduce carbon footprints.
• Shift towards renewable energy.
• Protect forests.
• Save energy.
• Adopt sustainable lifestyles.

Q6. The 2025 Punjab floods caused deaths, displacement, crop losses and damage to roads and bridges. Explain the natural and human causes of the disaster and suggest how better planning could reduce future damage.

Answer:

Natural causes:

• Very heavy monsoon rainfall.
• Western disturbances brought additional moisture and rainfall.
• Major rivers such as the Satluj, Beas and Ravi were already flowing high.
• Water from hills and local rainfall caused rivers to overflow.

Human causes:

• Weak and old river embankments.
• Houses and farms built too close to rivers.
• Silt accumulation reduced the capacity of rivers and dams.
• Flood warnings were late or poorly communicated.

Measures:

• Strengthen and maintain embankments.
• Improve drainage and river management.
• Prevent unsafe construction near rivers.
• Improve early-warning systems and disaster preparedness.

Q7. A school asks students to calculate their carbon footprints based on transport, electricity, water use and plastic consumption. Explain why these activities are connected to climate change.

Answer: These activities can contribute to greenhouse-gas emissions:

1. Private transport and flights use fossil fuels and release carbon dioxide.
2. Electricity use may indirectly cause emissions when electricity is produced using fossil fuels.
3. Wasting water increases the energy required for pumping, treatment and distribution.
4. Single-use plastics require energy for production and disposal.
5. Reducing these activities can lower an individual's carbon footprint.

The chapter therefore encourages practical lifestyle changes as part of climate action.

Q8. Why does India experience different seasons and why are these seasons important for people's lives?

Answer: India's climate is strongly influenced by the monsoon system.

The IMD broadly divides the year into:

1. Winter
2. Summer
3. Monsoon
4. Post-monsoon

Traditionally, Indian culture also recognises six ṛtus: spring, summer, monsoon, early autumn, late autumn and winter.

These seasonal changes influence:

• Agriculture and crop cycles
• Water availability
• Clothing and housing
• Festivals and cultural practices
• Employment and livelihoods
• Daily life

Thus, seasons are closely connected with both the natural environment and Indian society.

Q9. Why can monsoon be described as a “unifying climatic framework” for India despite large regional differences?

Answer: India has major differences in temperature and rainfall from one region to another. However:

• The monsoon affects almost the entire country.
• Agriculture in many regions depends on monsoon rainfall.
• Rivers, reservoirs and groundwater are replenished by rainfall.
• Monsoon influences economic activities, transport and livelihoods.
• The seasonal reversal of winds creates a broad annual rhythm across the country.

Therefore, although rainfall amounts differ greatly, the monsoon provides a common climatic framework linking different parts of India.

Q10. “Climate change is not only an environmental problem; it is also a social and economic problem.” Justify the statement.

Answer: Climate change affects several aspects of human life:

1. Agriculture: Changes in rainfall and temperature can reduce crop productivity.
2. Health: Heat and changing environmental conditions can increase health risks.
3. Livelihoods: Farmers, fishers and other climate-dependent workers may face losses.
4. Disasters: Floods, droughts and other extreme events can damage homes and infrastructure.
5. Inequality: Vulnerable groups, including women and children, can be particularly affected.

Therefore, climate change requires collective action, sustainable development and policies that protect both the environment and people's livelihoods.