Climate Change: Natural and Man-made Causes, Changes in India and Adaptation, ISC Class 11

What Climate Change is about

Weightage: CISCE gives no Class XI unit weightage for ISC Geography. Climate Change is topic 16 of the Class XI syllabus (Atmosphere) and can be asked anywhere in the 70-mark Paper I (Theory, 3 hours). Class XI is examined by the school, so your school sets the paper and decides how many marks each topic carries.Source: CISCE ISC Geography (853) syllabus, examination year 2028, Class XI

Key concepts

Natural causes of climatic change

1. Changes in solar output: the energy given out by the sun varies slightly, for example with the roughly 11-year sunspot cycle. Long periods of very few sunspots have coincided with cooler periods.
2. Changes in the earth's orbit and tilt (Milankovitch cycles): slow, regular changes in the shape of the earth's orbit (eccentricity), the tilt of its axis (obliquity) and the wobble of the axis (precession) alter how much sunlight reaches different latitudes in different seasons. They pace the advance and retreat of ice ages over tens of thousands of years.
3. Volcanic eruptions: large explosive eruptions throw sulphur dioxide high into the stratosphere, forming sulphate aerosols that reflect sunlight and cool the earth for a year or two. The eruption of Mount Pinatubo (Philippines) in 1991 cooled global temperatures for about two years.
4. Ocean circulation and El Nino: shifts in ocean currents redistribute heat; El Nino years tend to be warmer globally, La Nina years cooler.
5. Movement of continents and changes in mountains (over millions of years) alter ocean currents and winds.
6. Changes in the earth's surface: more snow and ice reflect more sunlight (higher albedo), cooling further; melting reduces albedo and adds warming (feedback).

These factors explain past ice ages and warm periods, but natural factors alone cannot explain the rapid warming since the mid-twentieth century.

Worked example

[4] Explain any four natural causes of climatic change. (Recall)

Try it first, then show the solutionSolution

1. Variation in solar output (sunspot cycles) - 1 mark.
2. Milankovitch cycles: orbit, tilt, wobble - 1 mark.
3. Volcanic aerosols reflect sunlight and cool the earth - 1 mark.
4. Ocean circulation changes (El Nino) or albedo feedback - 1 mark.

Answer: The sun's energy output varies slightly with sunspot activity; slow changes in the earth's orbit, tilt and wobble (Milankovitch cycles) change the distribution of sunlight and pace ice ages; large volcanic eruptions put sulphate aerosols into the stratosphere, reflecting sunlight and cooling the earth for a year or two; and changes in ocean circulation, such as El Nino, redistribute heat around the globe.

Man-made causes and the enhanced greenhouse effect

The greenhouse effect is natural: water vapour, carbon dioxide and other gases let sunlight in but absorb outgoing long-wave radiation, keeping the earth about 33 degrees C warmer than it would otherwise be. Human activities have increased these gases, strengthening the effect (the enhanced greenhouse effect) and causing global warming.

Man-made factors
1. Burning fossil fuels (coal, oil, natural gas) for electricity, industry and transport: the main source of carbon dioxide; atmospheric CO2 has risen from about 280 parts per million before the Industrial Revolution to over 400 ppm today.
2. Deforestation and land-use change: fewer trees to absorb CO2; burning forests releases carbon.
3. Agriculture: methane from flooded rice fields and cattle; nitrous oxide from nitrogen fertilisers.
4. Industry and waste: methane from landfills; CFCs and HFCs (also powerful greenhouse gases); cement production releases CO2.
5. Urbanisation: concrete and asphalt absorb heat, creating urban heat islands; vehicles and air-conditioners add heat.
6. Aerosols from pollution: some (sulphates) cool by reflecting sunlight, while black carbon (soot) warms and darkens snow and ice, speeding melting.

The main greenhouse gases are carbon dioxide, methane, nitrous oxide, CFCs and HFCs, and water vapour (which increases as the air warms, amplifying warming).

Worked example

[4] Explain how human activities are causing global warming. (Understanding)

Try it first, then show the solutionSolution

1. Burning fossil fuels releases CO2 - 1 mark.
2. Deforestation reduces absorption and releases carbon - 1 mark.
3. Agriculture and waste add methane and nitrous oxide - 1 mark.
4. More greenhouse gases trap more outgoing heat: enhanced greenhouse effect - 1 mark.

Answer: Burning coal, oil and gas releases carbon dioxide; cutting and burning forests both releases carbon and removes trees that absorb it; rice paddies, cattle, fertilisers and landfills add methane and nitrous oxide. These greenhouse gases absorb more of the long-wave radiation leaving the earth, strengthening the natural greenhouse effect and raising global temperatures.

Climatic changes in India

Observed and expected changes (based on India's own climate assessments)
1. Rising temperatures: India's average temperature rose by about 0.7 degrees C between 1901 and 2018, with more warm days and nights.
2. Heatwaves: more frequent, longer and more intense heatwaves in northern, central and eastern India, raising deaths from heatstroke and stress on power and water supply.
3. Monsoon rainfall: summer monsoon rainfall has become more erratic, with a decline over some regions such as the Indo-Gangetic plains in recent decades, longer dry spells and more frequent extreme rainfall events (very heavy rain on a single day), causing urban floods as in Mumbai and Chennai.
4. Droughts and floods: more frequent droughts in some regions and more intense floods in others.
5. Himalayan glaciers: many are retreating and thinning, threatening river flows in the long term and increasing risk of glacial lake outburst floods.
6. Sea-level rise and cyclones: rising seas threaten low coasts such as the Sundarbans; very severe cyclones over the Arabian Sea have become more frequent.
7. Effects: lower crop yields under heat stress, water scarcity, spread of vector-borne diseases, loss of biodiversity and damage to coastal livelihoods.

Worked example

[4] Describe four effects of climate change already observed in India. (Understanding)

Try it first, then show the solutionSolution

1. Rise in average temperature (about 0.7 degrees C, 1901-2018) - 1 mark.
2. More frequent and intense heatwaves - 1 mark.
3. Erratic monsoon, more extreme rainfall and floods - 1 mark.
4. Glacier retreat or sea-level rise threatening coasts - 1 mark.

Answer: India's average temperature has risen by about 0.7 degrees C since 1901; heatwaves have become more frequent and intense; the monsoon has become more erratic, with longer dry spells and more days of extreme rain causing floods; and Himalayan glaciers are retreating while rising seas and stronger cyclones threaten low-lying coasts such as the Sundarbans.

Adaptation in urban India

Cities concentrate people, heat and paved surfaces, so they face heatwaves, waterlogging and water shortages.

Measures
1. Heat action plans: early warnings, cooling centres, drinking-water points, changed working hours for outdoor workers and preparation of hospitals. Ahmedabad's Heat Action Plan (2013) was the first of its kind in South Asia and has been copied by many cities.
2. Cool roofs and green cover: reflective white roofs, rooftop gardens, urban forests and parks reduce indoor and outdoor temperatures and the urban heat island.
3. Water management: compulsory rainwater harvesting on buildings, recharge of groundwater, revival of lakes and tanks, reuse of treated wastewater.
4. Flood management: better storm-water drains, keeping natural drainage channels and wetlands free of encroachment, flood warning systems.
5. Climate-smart buildings and planning: energy-efficient design, natural ventilation, building codes, protection of mangroves along coastal cities.
6. Public transport and clean energy also cut emissions (mitigation) while reducing heat and pollution.

India's National Action Plan on Climate Change (2008) set up national missions, including one on sustainable habitat, that guide such work.

Worked example

[4] Suggest four measures Indian cities can take to adapt to more frequent heatwaves and extreme rainfall. (Evaluate)

Try it first, then show the solutionSolution

1. Heat action plans with early warnings and cooling centres - 1 mark.
2. Cool roofs, trees and parks to reduce the heat island - 1 mark.
3. Storm-water drains; protect wetlands and drainage channels - 1 mark.
4. Rainwater harvesting and groundwater recharge - 1 mark.

Answer: Cities can adopt heat action plans with early warnings, cooling centres and drinking-water points; use cool roofs, trees and parks to reduce the urban heat island; improve storm-water drainage and keep wetlands and natural channels free so heavy rain drains away; and make rainwater harvesting compulsory to recharge groundwater for dry spells.

Adaptation in rural India and practical work on rainfall

Rural adaptation (farming depends directly on climate)
1. Water conservation: watershed development, check dams, farm ponds, revival of traditional tanks and johads, and water-conservation works under rural employment schemes.
2. Efficient irrigation: drip and sprinkler irrigation to grow more crop per drop.
3. Climate-resilient crops: drought-, flood- and heat-tolerant varieties, changing sowing dates, crop diversification (millets, pulses) and mixed cropping.
4. Risk protection: crop insurance (such as the Pradhan Mantri Fasal Bima Yojana, 2016), weather-based advisories to farmers by mobile phone, and soil health cards.
5. Agroforestry and soil conservation: trees on farms, mulching and contour bunding protect soil and moisture.
6. Livelihood diversification: dairying, poultry and non-farm work to spread risk.

Practical work: measuring rainfall
1. A rain gauge is a cylindrical container with a funnel of known diameter leading into a collecting bottle. It is placed in an open space, away from trees and buildings, with its rim about 30 cm above the ground.
2. Each day at a fixed time, the collected water is poured into a measuring cylinder graduated in millimetres of rainfall.
3. Rainfall is expressed as the depth of water in mm that would cover a flat surface.
4. Bar graph: draw months on the x-axis and rainfall (mm) on the y-axis, with bars of equal width and gaps; give a title, scale and key. Comparing two cities' bars shows differences in monsoon pattern (for example a city with a single summer peak against one with rain in October-December).
5. Departure from normal (%) = (actual - normal) / normal x 100.

Worked example

[4] Explain how rainfall is measured with a rain gauge and how a bar graph of monthly rainfall is drawn. (Application)

Try it first, then show the solutionSolution

1. Rain gauge: funnel and collecting bottle in an open place, rim about 30 cm above ground - 1 mark.
2. Water measured daily at a fixed time in a cylinder graduated in mm - 1 mark.
3. Bar graph: months on x-axis, rainfall (mm) on y-axis, equal bars - 1 mark.
4. Title, scale and key; compare peaks between cities - 1 mark.

Answer: A rain gauge, a funnel leading into a collecting bottle, is set in an open place with its rim about 30 cm above the ground; each day at a fixed time the water is poured into a measuring cylinder graduated in millimetres. For a bar graph, months are marked on the x-axis and rainfall in mm on the y-axis, with bars of equal width, a title, a scale and a key.

Climate Change in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Climate Change in India, Adaptation and Rainfall Practical
• Natural and Man-made Causes of Climate Change

Climate Change: key facts

Natural causes

Solar output, Milankovitch cycles, volcanoes, ocean circulation, albedo feedback

Pinatubo 1991 cooled the earth.

Man-made causes

Fossil fuels, deforestation, agriculture, industry/waste, urbanisation

CO2 280 ppm -> over 400 ppm.

Changes in India

+0.7 degrees C (1901-2018), heatwaves, erratic monsoon, extreme rain, glacier retreat, sea-level rise

Climate assessment for the Indian region.

Adaptation

Urban: heat action plans, cool roofs, drains, rainwater harvesting; rural: watersheds, drip irrigation, resilient crops, insurance

NAPCC 2008.

Rainfall departure

$Departure($

620 vs 800 mm = -22.5%.

Mean monthly rainfall

$Mean=total/numberofmonths(oryears)$

For bar graphs.

How the school exam asks Climate Change

The question patterns to expect, and the method that works for each.

Tricks to remember Climate Change

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Natural causes: 'SOVO'

  Sun, Orbit, Volcanoes, Oceans.

  Use it when: Natural factors.

• Man-made: 'FDAIU'

  Fuels, Deforestation, Agriculture, Industry, Urbanisation.

  Use it when: Human factors.

• Adapt versus mitigate

  Mitigation Minimises the cause; Adaptation Adjusts to the effect.

  Use it when: Avoid mixing the two.

Climate Change: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section D style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 8-mark question split into 2 + 2 + 2 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Climate Change

The slips examiners see most often, and what to write instead.

• ✗Mistake: Confusing ozone depletion with global warming

  Both are atmospheric problems.

  Wrong working

  The ozone hole causes global warming.

  Right working

  Global warming is caused by greenhouse gases; ozone depletion lets in more UV.

  ✓Do this: Keep the two causes and effects separate.

  Usually costs: 1-2 marks.

• ✗Mistake: Listing mitigation when adaptation is asked

  Terms mixed.

  ✓Do this: Adaptation = coping (drains, crops, heat plans); mitigation = cutting emissions.

  Usually costs: 1-2 marks.

• ✗Mistake: Saying the greenhouse effect is entirely harmful

  Natural effect forgotten.

  ✓Do this: It keeps the earth habitable; the problem is its enhancement.

  Usually costs: 1 mark.

• ✗Mistake: Bar graph without scale or title

  Presentation marks lost.

  ✓Do this: Label axes, give a scale, a title and a key.

  Usually costs: 1 mark.

• ✗Mistake: No Indian reference

  The syllabus asks for India.

  ✓Do this: Heatwaves, monsoon, glaciers, Ahmedabad plan, farm ponds, NAPCC.

  Usually costs: 1 mark.

Practice questions on Climate Change

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · Very short answerExam level

   Distinguish between weather and climate in one sentence.

   Hint

   Time span.

   Answer

   Weather is the short-term state of the atmosphere; climate is the average weather over a long period (about 30 years or more).

2. Q2 · 1 mark · Very short answerExam level

   Name the main greenhouse gas released by burning fossil fuels.

   Hint

   CO2.

   Answer

   Carbon dioxide.

3. Q3 · 1 mark · MCQExam level

   Methane is released in large amounts by:
   (a) Wind turbines
   (b) Flooded rice fields and cattle
   (c) Solar panels
   (d) Forests growing

   Hint

   Agriculture.

   Answer

   (b) Flooded rice fields and cattle.

4. Q4 · 1 mark · Very short answerHarder exam level

   Which Indian city prepared South Asia's first heat action plan?

   Hint

   Gujarat, 2013.

   Answer

   Ahmedabad.

5. Q5 · 4 marks · Short answerHarder exam level

   [4] Explain how Milankovitch cycles cause climatic change.

   Hint

   Orbit, tilt, wobble.

   Answer

   (1) The shape of the earth's orbit changes slowly between more circular and more elliptical (eccentricity). (2) The tilt of the axis varies slightly (obliquity). (3) The axis wobbles, changing the season when the earth is nearest the sun (precession). (4) Together they alter the amount of summer sunlight in high latitudes over tens of thousands of years, pacing ice ages.

6. Q6 · 4 marks · Short answerHarder exam level

   [4] Why are Himalayan glaciers important, and how does climate change threaten them?

   Hint

   Rivers.

   Answer

   (1) They feed perennial rivers like the Ganga and Indus, especially in the dry pre-monsoon season. (2) Warming makes many of them retreat and thin. (3) Black carbon (soot) darkens the ice and speeds melting. (4) In the long term river flows may fall, while meltwater lakes dammed by moraines can burst and flood valleys.

7. Q7 · 4 marks · Short answerHarder exam level

   [4] Explain why coastal cities like Mumbai are vulnerable to climate change, and suggest two adaptations.

   Hint

   Rain, sea.

   Answer

   (1) Extreme rainfall events overwhelm drains and flood low-lying areas. (2) Rising sea level and storm surges threaten reclaimed land and coastal settlements. (3) Adaptation: improve storm-water drains and keep natural channels and wetlands clear. (4) Protect and restore mangroves, which absorb surge energy, and set up flood warnings.

8. Q8 · 4 marks · Short answerHOTS / competency

   [4] A city's normal annual rainfall is 1,500 mm. Over three years it receives 1,140 mm, 1,725 mm and 1,500 mm. Calculate the percentage departure for each year and the three-year average.

   Hint

   (actual - normal) / normal x 100.

   Answer

   (1) Year 1: (1,140 - 1,500)/1,500 x 100 = -24 per cent. (2) Year 2: (1,725 - 1,500)/1,500 x 100 = +15 per cent. (3) Year 3: 0 per cent. (4) Average = (1,140 + 1,725 + 1,500)/3 = 4,365/3 = 1,455 mm, which is 3 per cent below normal; the swings show increasing variability.

9. Q9 · 4 marks · Short answerHOTS / competency

   [4] 'Adaptation is necessary even if all emissions stopped today.' Evaluate this statement.

   Hint

   Lag; long-lived gases.

   Answer

   (1) Carbon dioxide stays in the atmosphere for a very long time, so existing gases will keep warming the earth. (2) Oceans warm slowly and sea level will go on rising for decades. (3) Heatwaves, erratic monsoons and glacier retreat are already affecting India. (4) So the statement is valid: mitigation limits future change, but adaptation is needed to cope with changes already locked in.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.What was the pre-industrial level of carbon dioxide?Show answer

   About 280 parts per million.

2. 2.Which eruption of 1991 cooled the earth?Show answer

   Mount Pinatubo, Philippines.

3. 3.When did India release its National Action Plan on Climate Change?Show answer

   2008.

4. 4.At what height is a rain gauge's rim usually kept?Show answer

   About 30 cm above the ground.

5. 5.What is an urban heat island?Show answer

   A city area warmer than its surroundings because of paved surfaces, buildings and waste heat.

6. 6.By about how much did India's average temperature rise from 1901 to 2018?Show answer

   About 0.7 degrees C.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Climate = average weather over about 30 years; recent warming is rapid.
• ☐Natural: sun, Milankovitch cycles, volcanoes (Pinatubo 1991), ocean circulation, albedo.
• ☐Man-made: fossil fuels (CO2 280 -> 400+ ppm), deforestation, methane, nitrous oxide, HFCs, urban heat.
• ☐India: +0.7 degrees C (1901-2018), heatwaves, erratic monsoon, extreme rain, glacier retreat, sea-level rise.
• ☐Urban adaptation: heat action plans (Ahmedabad 2013), cool roofs, trees, drains, rainwater harvesting.
• ☐Rural adaptation: watersheds, farm ponds, drip irrigation, resilient crops, insurance, advisories.
• ☐Rain gauge: open site, rim ~30 cm; measure daily in mm; bar graph with title, scale, key.
• ☐Departure (%) = (actual - normal)/normal x 100.

Climate Change: frequently asked questions