GeographyISC Class 11 · Climate Change

Natural and Man-made Causes of Climate Change (ISC Class 11 Geography)

Updated 17 October 2026 · Fact-checked

Climate is the average weather over 30 years or more. Natural causes include changes in solar output, Milankovitch cycles, volcanic eruptions such as Pinatubo in 1991, ocean circulation and albedo changes; recent rapid warming is mainly due to man-made greenhouse gases from fossil fuels, deforestation, agriculture and industry.

Natural causes act slowly, but the thick orange arrows show man-made greenhouse gases drive the rapid warming since the mid-twentieth century.

Illustration drawn for QuestionBuddy.

Understand Natural and Man-made Causes of Climate Change

Weather and climate. Weather is the state of the atmosphere over hours or days; climate is the average weather over a long period, usually 30 years or more.

Natural causes.
1. Solar output varies slightly, for example in the 11-year sunspot cycle.
2. Milankovitch cycles: eccentricity of the orbit, tilt (obliquity) and wobble (precession) change sunlight by latitude and season and pace ice ages.
3. Volcanic eruptions: sulphur dioxide forms sulphate aerosols that reflect sunlight and cool the earth for a year or two; Pinatubo (1991) cooled temperatures for about two years.
4. Ocean circulation and El Nino: El Nino years tend to be warmer, La Nina cooler.
5. Movement of continents and mountains over millions of years alters currents and winds.
6. Surface changes: snow and ice raise albedo (cooling) and melting reduces it (warming feedback).
These cannot explain the rapid warming since the mid-twentieth century.

Man-made causes. The greenhouse effect keeps the earth about 33 degrees C warmer; humans strengthen it.
1. Fossil fuels: main source of CO2, up from about 280 ppm before the Industrial Revolution to over 400 ppm.
2. Deforestation and land-use change.
3. Agriculture: methane from rice fields and cattle, nitrous oxide from fertilisers.
4. Industry and waste: methane from landfills, CFCs, HFCs and cement CO2.
5. Urbanisation: heat islands.
6. Aerosols: sulphates cool; black carbon warms and speeds ice melt.
Main gases: CO2, methane, nitrous oxide, CFCs and HFCs, and water vapour as an amplifier.

Natural and Man-made Causes of Climate Change: key facts

Natural causes: Solar output
Milankovitch cycles
Volcanoes
Ocean circulation
Albedo
Man-made causes: Fossil fuels
Deforestation
Agriculture
Industry and waste
Urbanisation
CO2 rise: $A b o u t 280 pp m ∣ O v er 400 pp m$; Increase is over 120 ppm.
Greenhouse effect: About 33 degrees C natural warming | Enhanced by human gases

How to answer Natural and Man-made Causes of Climate Change questions

Questions are 4 marks (natural versus man-made) or 7 marks combined with India and adaptation.

1Define climate in one line.
2List natural causes with one clause each.
3List man-made causes with the gas involved.
4Conclude why natural factors alone cannot explain recent warming.

Natural and Man-made Causes of Climate Change in real life

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

Rise in carbon dioxide

Suppose a chart shows carbon dioxide rising from 280 ppm to 400 ppm.

Find the increase and the percentage rise.

Try it first, then show the solutionSolution

Increase = 400 - 280 = 120 ppm.
Percentage = 120/280 x 100 = 42.9 per cent.

Answer: 120 ppm; about 42.9 per cent.

Memory hook: Change over original.

Volcano cooling

Suppose a big eruption throws sulphur gases into the stratosphere and the next two summers are slightly cooler.

Name the effect.

Try it first, then show the solutionSolution

Sulphur forms sulphate aerosols that reflect sunlight.
Global temperature falls for a year or two, as after Pinatubo 1991.

Answer: Aerosol cooling.

Memory hook: Ash cloud, sunshade.

Tricks to remember Natural and Man-made Causes of Climate Change

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

SMOVA
Solar, Milankovitch, Ocean, Volcano, Albedo: the natural causes.
Use it when: Natural list.
FDAIU
Fuels, Deforestation, Agriculture, Industry, Urbanisation.
Use it when: Man-made list.

Natural and Man-made Causes of Climate Change: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Greenhouse gas source · 1 mark · MCQBoard level

Methane in agriculture is mainly released from:
(a) wind turbines
(b) flooded rice fields and cattle
(c) solar panels
(d) tractors only

Try it first, then show the solutionSolution

Wet fields and livestock.

Answer: (b) Flooded rice fields and cattle.

Example 2: Weather versus climate · 2 marks · Short answerBoard level

Distinguish between weather and climate.

Try it first, then show the solutionSolution

Weather: atmosphere over hours or days.
Climate: average weather over 30 years or more.

Answer: Weather is short term; climate is the long-term average.

Example 3: CO2 trend · 4 marks · Long answerHarder board level

Carbon dioxide rose from about 280 ppm to 400 ppm. Calculate the increase and percentage rise, and name two man-made sources responsible.

Try it first, then show the solutionSolution

Increase = 400 - 280 = 120 ppm.
Percentage = 120/280 x 100 = 42.86, about 42.9 per cent.
Source 1: burning fossil fuels.
Source 2: deforestation or cement production.

Answer: 120 ppm; about 42.9 per cent; fossil fuels and deforestation.

Example 4: Milankovitch · 4 marks · Long answerHarder board level

Explain three Milankovitch cycles and their effect on climate.

Try it first, then show the solutionSolution

Eccentricity: the shape of the orbit changes.
Obliquity: the tilt of the axis changes.
Precession: the axis wobbles.
They alter sunlight by latitude and season and pace ice ages over tens of thousands of years.

Answer: Orbit shape, tilt and wobble alter sunlight and pace ice ages.

Example 5: Natural or human? · 5 marks · Case-basedHOTS / competency

Case: A scientist argues that solar variation and Milankovitch cycles are too slow or too small to explain warming since the mid-twentieth century. (a) Name two natural factors. (b) State what the argument implies about the cause. (c) Name two man-made sources of methane.

Try it first, then show the solutionSolution

(a) Solar output and Milankovitch cycles (also volcanoes).
(b) Recent warming is mainly man-made greenhouse gas increase.
(c) Flooded rice fields, cattle or landfills.

Answer: (a) Solar, Milankovitch (b) mainly man-made greenhouse gases (c) rice fields and landfills.

Where students lose marks in Natural and Man-made Causes of Climate Change

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

Mistake: Giving natural causes as the main modern cause
Evidence is ignored.
Do this: Natural factors cannot explain the rapid warming; man-made greenhouse gases do.
Usually costs: 2 marks.
Mistake: Percentage over final value
Change is divided by 400.
Wrong working
120/400 = 30%
Right working
120/280 = 42.9%
Do this: Divide by the original: 120/280.
Usually costs: 1 mark.
Mistake: Mixing aerosols
All aerosols are said to warm.
Do this: Sulphates cool; black carbon warms.
Usually costs: 1 mark.

Exam tips

Define climate as 30 years or more.
Give Pinatubo 1991 for volcanoes.
Name the gas with each man-made source.
End with why natural causes are insufficient.

Practice questions on Natural and Man-made Causes of Climate Change

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

Q1 · 1 mark · MCQBoard level
The 1991 eruption that cooled global temperatures for about two years was of:
(a) Etna
(b) Pinatubo
(c) Krakatoa
(d) Fujiyama
Hint
Philippines.
Answer
(b) Pinatubo.
Q2 · 3 marks · Short answerHarder board level
Explain how melting ice leads to further warming.
Hint
Albedo feedback.
Answer
Snow and ice reflect sunlight; as they melt, the darker surface absorbs more heat, causing more warming and more melting.
Q3 · 4 marks · Long answerHarder board level
Explain the enhanced greenhouse effect.
Hint
33 degrees C natural.
Answer
Natural greenhouse gases keep the earth about 33 degrees C warmer. Human activities have increased gases such as CO2 and methane, which absorb more outgoing radiation and strengthen the effect.
Q4 · 3 marks · Short answerHarder board level
Distinguish between the warming effect of black carbon and the cooling effect of sulphate aerosols.
Hint
Reflect versus absorb.
Answer
Sulphates reflect sunlight and cool; black carbon absorbs sunlight, warms the air and darkens snow, speeding melting.
Q5 · 4 marks · Case-basedHOTS / competency
Case: Atmospheric CO2 is 280 ppm in one century and 420 ppm later. (a) Find the percentage rise. (b) Name the gas amplified by warming. (c) Name two sectors responsible.
Hint
140/280.
Answer
(a) 140/280 x 100 = 50 per cent. (b) Water vapour. (c) Energy (fossil fuels) and land-use change or agriculture.

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.Climate averaging period?Show answer
30 years or more.
2.Natural greenhouse warming?Show answer
About 33 degrees C.
3.El Nino years are?Show answer
Generally warmer.
4.Main CO2 source?Show answer
Fossil fuels.
5.Sunspot cycle?Show answer
About 11 years.

Natural and Man-made Causes of Climate Change: frequently asked questions

Is the greenhouse effect bad?

No, the natural effect keeps earth habitable; the enhanced effect is the problem.

Do volcanoes warm or cool?

Large eruptions cool for a year or two.

What is mitigation?

Reducing the causes, such as emissions.