Example 1: rate of change
CO₂ rose from 369.7 ppm in 2000 to 389.9 ppm in 2010. Calculate the mean rate of increase.
- Increase = 389.9 − 369.7 = 20.2 ppm.
- Rate = 20.2 ÷ 10 = 2.02 ppm per year.
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IB DemystifiedMYP Sciences
Climate change and the greenhouse effect
In 1960, the air contained about 317 molecules of carbon dioxide in every million. Today it is over 420. That small change in an invisible gas is warming the planet, raising the seas and intensifying floods and heatwaves, and understanding why is the first step to responding well.
Recommended for MYP 4 · eAssessment priority · About 3 lessons · Criteria A, B, C and D
On this page
- Learning objectives
- Before you start
- Key vocabulary
- Understanding climate change
- Evidence, impacts and responses
- Climate change in the real world
- Worked examples
- In the eAssessment
- Check your understanding
- Practice questions
- Investigation
- Criterion-linked questions
- Challenge questions
- Topic check
- Review your mistakes
- Your progress
Learning objectives
By the end of this topic you should be able to:
- explain the greenhouse effect using visible and infrared radiation
- describe natural and human sources and sinks of greenhouse gases
- interpret evidence for climate change, including CO₂ records and ice cores
- explain impacts such as sea-level rise, extreme weather and ocean acidification
- distinguish mitigation from adaptation and evaluate responses
- distinguish weather from climate and evaluate common claims using evidence
Before you start
You will use these skills. If any feel shaky, review them first.
- the electromagnetic spectrum, including infrared (see EM spectrum)
- thermal energy transfer and radiation from surfaces (see Thermal energy transfer)
- photosynthesis, respiration and combustion
Key vocabulary
- Greenhouse gas
- A gas that absorbs and re-emits infrared radiation, such as carbon dioxide, methane and water vapour.
- Enhanced greenhouse effect
- Extra warming caused by human increases in greenhouse gases.
- Carbon sink
- Something that removes and stores carbon, such as forests, soils and oceans.
- Feedback
- A change caused by warming that increases (positive) or reduces (negative) further warming.
- Mitigation / adaptation
- Reducing the causes of climate change / adjusting to its effects.
- Weather / climate
- Short-term conditions in one place / the long-term average (about 30 years) over a region.
Understanding climate change
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What is it?
Sunlight, mostly visible light, passes through the atmosphere and warms the Earth's surface. The warm surface gives out infrared. Greenhouse gases absorb much of this infrared and re-emit it, some back towards the surface. This natural greenhouse effect keeps Earth about 33 °C warmer than it would otherwise be.
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Why is it changing?
Burning fossil fuels, cutting down forests and farming have added carbon dioxide, methane and other gases faster than natural sinks can absorb them. More greenhouse gas means less infrared escapes to space, so the Earth gains energy and warms until a new balance is reached. Feedbacks, such as melting ice and more water vapour, amplify the warming.
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How do we know?
In 1856 Eunice Foote showed that CO₂ traps heat, and John Tyndall measured infrared absorption by gases in 1859. Since 1958, Charles David Keeling's measurements at Mauna Loa have tracked rising CO₂. Ice cores reveal CO₂ over 800 000 years, and temperature records, satellites, glaciers and sea-level gauges show the warming.
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Why does it matter?
Global temperature has risen by about 1.1 °C since the late 1800s. Heatwaves and heavy rainfall are becoming more intense, sea level has risen about 20 cm since 1901, and oceans are becoming more acidic. Vulnerable communities, often those who emitted least, are hit hardest.
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What does it connect to?
Climate change links to radiation and energy in physics; to combustion, fuels and acids in chemistry; to photosynthesis, ecosystems and evolution in biology; and to economics, ethics and politics.
Evidence, impacts and responses
- Evidence: rising CO₂ (from about 280 ppm before industry to over 420 ppm today), rising global temperatures, shrinking glaciers and Arctic sea ice, rising sea level and ocean heat.
- Impacts: more intense heatwaves, droughts and floods; sea-level rise from thermal expansion and melting land ice; ocean acidification; shifting habitats and crop yields.
- Mitigation: renewable energy, efficiency, protecting forests, cutting methane, changing diets and transport.
- Adaptation: flood defences, heat action plans, drought-resistant crops, early-warning systems.
The Paris Agreement (2015) aims to keep warming well below 2 °C and to pursue efforts to limit it to 1.5 °C.
Climate change in the real world
In 2022, floods covered about a third of Pakistan and affected about 33 million people, even though Pakistan produces less than 1% of global emissions. Glaciers in the Himalaya, Karakoram and Hindu Kush, which feed the Indus and other great rivers, are shrinking. Cities worldwide are building heat action plans, and many countries are rapidly expanding solar and wind power.
Worked examples
Example 2: mitigation or adaptation?
Classify: (a) restoring mangrove forests on a coast; (b) switching buses to electric.
- (a) Mangroves protect coasts from storm surges (adaptation) and store carbon (mitigation): both.
- (b) Electric buses cut emissions if the electricity is low-carbon: mitigation.
In the eAssessment
Climate questions are ideal for integrated tasks, combining physics, chemistry, biology and decisions. Expect:
- Explain the greenhouse effect precisely: visible in, infrared out, absorbed and re-emitted.
- Analyse real data such as CO₂ records: changes, rates and percentage increases.
- Evaluate models such as bottle experiments, and evaluate claims using evidence.
- Discuss responses, weighing science, fairness, cost and effectiveness.
Common ways to lose marks: confusing the greenhouse effect with the ozone hole; saying greenhouse gases trap incoming sunlight; confusing weather with climate; and saying melting sea ice is the main cause of sea-level rise.
Check your understanding
Quick questions on the ideas above. Try each one before using a hint.
Practice questions
Investigation: does warmer water hold less carbon dioxide?
Partially guided investigation · about 50 minutes · pairs
- Research question
- How does the temperature of carbonated water (5, 15, 25, 35 and 45 °C) affect the mass of carbon dioxide it loses in 20 minutes after opening?
- Scientific background
- Oceans absorb about a quarter of the carbon dioxide humans release. The amount of gas that can stay dissolved in water depends on temperature, so warming oceans may absorb less CO₂. Carbonated water contains dissolved CO₂ that escapes when the bottle is opened.
- Hypothesis
- Write your own prediction, with a scientific justification.
- Variables
- Identify your independent, dependent and control variables, and explain how you will control them.
- Apparatus
- Small unopened bottles of the same carbonated water, water baths at different temperatures, thermometer, balance (0.01 g), stopwatch, paper towels.
- Method
- Stand each bottle in a water bath until it reaches the bath temperature.
- Dry the bottle, open it, pour exactly 100 g into a beaker on the balance and record the mass.
- Record the mass again after 20 minutes; the loss is mostly carbon dioxide.
- Repeat three times at each temperature and calculate the mean mass lost.
Safety. Open bottles slowly, pointing them away from people, as warm bottles can fizz strongly. Do not heat sealed bottles above 45 °C. Wipe up spills near the balance, and do not drink anything in the laboratory.
Then evaluate: some mass is also lost by evaporation of water. How could you estimate and correct for this?
Criterion-linked questions
Criterion B: inquiring and designing
Criterion C: processing and evaluating
Criterion D: reflecting on the impacts of science
Challenge questions
Harder problems in unfamiliar contexts. Plan before you calculate.
Topic check
Five questions picked at random from the whole topic. Take a new set whenever you like.
Review your mistakes
Questions you got wrong on this device appear here so you can try them again. Answer one correctly and it leaves the list.
Your progress
Tracked separately for each skill, on this device only.
| Skill | Correct | Status |
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