In simple terms
A friendly intro before the formal notes — no formulas yet.
Our Planet's Energy Bill
Our global energy choices have put the Earth's climate system into 'overdraft'. We'll explore how our reliance on certain energy sources is raising the planet's temperature and what we can do to balance the books.
Imagine your personal health. Relying on fossil fuels is like a diet of only fast food and sugary drinks; it gives you a quick energy boost but leads to long-term health problems like a high fever (global warming). Switching to renewable energy is like adopting a balanced diet and exercise plan; it's a sustainable way to stay healthy and avoid a crisis.
- 1
Connect our daily energy use (electricity, transport) to specific sources like coal, oil, gas, and renewables.
- 2
Understand how burning fossil fuels releases greenhouse gases, trapping more heat in the atmosphere—the enhanced greenhouse effect.
- 3
Examine the consequences: rising sea levels, more extreme weather, and threats to food and water security.
- 4
Compare and evaluate solutions, from global agreements and carbon taxes (mitigation) to building sea walls (adaptation).
Simulations
Every simulation here runs the real model — try the steps on a card, then check what you see against the notes.
1 simulation
- PhETIB 7.1
Greenhouse Effect
Sunlight in, infrared out: set the greenhouse gas concentration by date and read the surface temperature.
Try this
- Start the sunlight and let the temperature settle.
- Step the greenhouse gas concentration from 1750 to 1950 to 2020.
- Compare the infrared leaving the atmosphere each time.
Look for More greenhouse gas traps more outgoing infrared, so the surface settles at a higher temperature — the mechanism behind the emissions choices in this lesson.
Simulation by PhET Interactive Simulations, University of Colorado Boulder · Licensed to MarkScheme (public licence CC BY-NC 4.0 since 2026-03-30)
Full topic notes
Formal explanation with the rigour you need for the exam.
Energy Choices and Greenhouse Gas Emissions
The global energy system is dominated by three main fossil fuels: coal, oil, and natural gas. When these fuels are combusted to release energy, they also release greenhouse gases (GHGs) into the atmosphere. The most significant of these is carbon dioxide (), but methane () and nitrous oxide () are also major contributors. While the natural greenhouse effect is essential for life, the additional GHGs from human (anthropogenic) activities have intensified this effect, leading to global warming and climate change.
Fossil Fuels: Account for over 80% of global energy consumption and are the largest source of anthropogenic GHG emissions.
Electricity Generation: Coal-fired power plants are a major source of .
Transport: Cars, lorries, ships, and aeroplanes predominantly run on oil-based fuels like petrol and diesel.
Industry & Agriculture: Industrial processes and agricultural practices (e.g., livestock farming, rice paddies, fertiliser use) release significant amounts of and .
Deforestation: Clearing forests reduces the planet's capacity to absorb through photosynthesis.
Impacts of Climate Change
The consequences of a warming planet are far-reaching and interconnected, affecting both natural ecosystems and human societies. These impacts are not distributed evenly; low-income nations and vulnerable communities often bear the brunt of the effects, despite having contributed least to the problem. Key impacts include rising sea levels from thermal expansion of water and melting ice caps, increased frequency and intensity of extreme weather events like hurricanes and heatwaves, disruption to agriculture and food security, and threats to biodiversity as habitats change faster than species can adapt.
Responding to Climate Change: Mitigation and Adaptation
Human responses to climate change fall into two main categories. Mitigation focuses on tackling the causes of climate change by reducing or preventing GHG emissions. It is a global-scale problem requiring global-scale solutions. Adaptation involves adjusting our societies and ecosystems to cope with the unavoidable impacts of climate change that are already happening or are expected in the future. Adaptation is often more local or regional in its implementation. A comprehensive climate strategy requires both mitigation to prevent the unmanageable and adaptation to manage the unavoidable.
Mitigation Examples: Reducing energy consumption, switching to renewable energy sources (solar, wind), carbon capture and storage (CCS), afforestation, promoting public transport, and implementing carbon taxes or trading schemes.
Adaptation Examples: Building sea walls and flood defences, developing drought-resistant crops, managing water resources more effectively, creating early warning systems for extreme weather, and planned relocation of vulnerable communities.
Synergy: Some strategies can have both mitigation and adaptation benefits. For example, planting mangrove forests can sequester carbon (mitigation) and protect coastlines from storm surges (adaptation).
In Paper 2, when asked to 'evaluate' or 'discuss' climate change strategies, you must provide a balanced argument. This means outlining both the strengths and weaknesses or arguments for and against a particular approach. Use specific, named examples. For instance, instead of just 'renewable energy', discuss 'the Hornsea Wind Farm project in the UK' or 'the Noor Ouarzazate Solar Complex in Morocco'. A concluding statement that summarises your judgement is essential for top marks.
Worked examples
See the formulas applied — reveal one step at a time, like the exam.
A UK household consumes 3,500 kWh of electricity per year. The national grid has an emission factor of 0.233 kg e per kWh. If the household installs solar panels that generate 3,000 kWh per year (with a lifecycle emission factor of 0.045 kg e/kWh) and imports the remaining 500 kWh from the grid, calculate the annual reduction in carbon dioxide equivalent (e) emissions. [3 marks]
- 1
Calculate initial emissions:
Evaluate the use of carbon taxes as a strategy for mitigating climate change. [9 marks]
- 1
A carbon tax is a market-based mitigation strategy that puts a direct price on carbon dioxide emissions, aiming to reduce them by making polluting activities more expensive. Its effectiveness can be evaluated by considering its strengths and weaknesses.
How it all connects
The big idea sits in the middle — tap a linked idea to explore the link.
Tap a linked idea to see how it connects back to the main topic — that connection is what examiners reward.
Glossary
Key terms for this topic — skim now; the Check step will test them.
- Mitigation
Human responses to climate change fall into two main categories. Mitigation focuses on tackling the causes of climate change by reducing or preventing GHG emissions. It is a global-scale problem requiring global-scale solutions. Adaptation involves adjusting our societies and ecosystems to cope with the unavoidable impacts of climate change that are already happening or are expected in the future.
- Mitigation (Climate Change)
Strategies that aim to reduce or prevent the emission of greenhouse gases, tackling the root cause of climate change. Examples: switching to renewable energy, improving energy efficiency, afforestation.
- Adaptation (Climate Change)
Strategies that aim to manage the adverse effects of climate change and reduce vulnerability. It involves adjusting to the actual or expected future climate. Examples: building sea walls, developing drought-resistant crops, early warning systems for floods.
- Enhanced Greenhouse Effect
The increased warming of the Earth's atmosphere caused by human activities adding extra greenhouse gases (like from burning fossil fuels), which trap more outgoing long-wave radiation.
- Natural Greenhouse Effect
The natural process where certain gases in the atmosphere trap heat, keeping the Earth warm enough for life. Without it, the Earth's average temperature would be about -18°C.
- Carbon Tax
A fee imposed on the burning of carbon-based fuels (coal, oil, gas). It is a market-based mitigation strategy that follows the 'polluter pays principle' to discourage GHG emissions.
- Carbon Trading (Cap-and-Trade)
A market-based system where a government sets a cap on total emissions and issues permits to pollute. Companies can buy and sell these permits, creating a financial incentive to reduce emissions.
- Albedo
The measure of how much light that hits a surface is reflected without being absorbed. Light-coloured surfaces (ice, snow) have high albedo, while dark surfaces (oceans, forests) have low albedo. Melting ice reduces Earth's albedo, creating a positive feedback loop.
- Positive Feedback Loop (Climate)
A cycle where the effects of a change in a system amplify the original change, leading to further deviation from the initial state. Example: Melting permafrost releases methane, which causes more warming, which melts more permafrost.
- IPCC
The Intergovernmental Panel on Climate Change. It is the UN body for assessing the science related to climate change, providing policymakers with regular scientific assessments on impacts and options.
- Geo-engineering
Large-scale, deliberate manipulation of the Earth's climate system to counteract the effects of climate change. Examples include solar radiation management (e.g., stratospheric aerosols) and carbon dioxide removal.
- Paris Agreement (2015)
A landmark international treaty on climate change. Its goal is to limit global warming to well below 2 degrees Celsius, preferably to 1.5 degrees Celsius, compared to pre-industrial levels.
Name it
Read the meaning, then pick which of this lesson’s terms it describes. Miss one and you see what your choice really means.
Strategies that aim to reduce or prevent the emission of greenhouse gases, tackling the root cause of climate change. Examples: switching to renewable energy, improving energy efficiency, afforestation.
Quick check
Write your answer first, then compare it with the model one — the gap is what you would have lost.
Teach it back
If you can explain it simply, you own it — gaps here are marks you’d lose.
Teach it back
Explain this topic as if teaching a friend. We name the gaps an examiner would still dock.
Revision flashcards
Guess first, then flip — retrieval beats re-reading.
Key takeaways
Review these before you close the topic — retrieval beats re-reading.
Fossil Fuels: Account for over 80% of global energy consumption and are the largest source of anthropogenic GHG emissions.
Electricity Generation: Coal-fired power plants are a major source of .
Transport: Cars, lorries, ships, and aeroplanes predominantly run on oil-based fuels like petrol and diesel.
Industry & Agriculture: Industrial processes and agricultural practices (e.g., livestock farming, rice paddies, fertiliser use) release significant amounts of and .
Deforestation: Clearing forests reduces the planet's capacity to absorb through photosynthesis.
Practice — then mark it
The whole point: a real Cambridge question, marked mark-by-mark.
Test Your Knowledge on Climate Change & Energy
Test Your Knowledge on Climate Change & Energy
Extra simulations & links
PhET, GeoGebra and other curated tools — open in a new tab.
Frequently asked
Checkpoint
One marked question is worth ten re-reads — close the loop before you move on.
Reading it isn’t knowing it — prove it.
Before you move on: do Test Your Knowledge on Climate Change & Energy on paper, snap a photo, and get examiner-style feedback on exactly where you win and lose marks.
Discuss Climate change, energy production, and human systems
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