This mini-lesson covers the Hazardous Earth weather content: how the climate has changed over time, its natural and human causes, the evidence, the global atmospheric circulation, and two weather hazards — tropical cyclones and drought.
Work through each screen, answer the questions as you go (multiple-choice, numeric, short-answer and games) and collect ⭐ stars. Press Start when you're ready.
Climate over time
The climate has always changed
Earth's climate has shifted between colder glacial periods and warmer interglacial periods throughout the Quaternary (the last ~2.6 million years).
The last glacial maximum (the last "Ice Age" peak) was around 20,000 years ago.
We are now in a warmer interglacial, but average temperatures have risen sharply since about 1850 (the start of industrialisation).
Key idea: natural climate change is nothing new — but the rate of recent warming is unusually fast, and lines up with rising CO₂ from human activity.
Natural causes
Natural causes of climate change
Before humans, natural factors drove climate change:
Milankovitch cycles — long-term changes in the shape of Earth's orbit, tilt and wobble, altering how much solar energy reaches Earth (cycles of ~100,000, ~41,000, ~26,000 years).
Solar output — the Sun's energy varies (e.g. sunspot cycles); fewer sunspots = slightly cooler.
Volcanic activity — large eruptions throw ash and sulphur dioxide into the stratosphere, reflecting sunlight and cooling the planet for a year or two.
Human causes & evidence
The enhanced greenhouse effect
Since 1850, humans have added greenhouse gases (mainly CO₂ and methane) to the atmosphere by burning fossil fuels, deforestation, farming and industry. These trap more outgoing heat — the enhanced greenhouse effect — warming the planet.
Evidence that the climate is changing:
Ice cores — trapped air bubbles show past CO₂ and temperature over hundreds of thousands of years.
Global temperature records, shrinking glaciers and Arctic sea ice, and rising sea levels.
Tree rings and pollen preserved in sediment.
Quick check
Natural or human cause?
?Which of these is a natural cause of climate change (not a human one)?
Global circulation
The global atmospheric circulation
The uneven heating of Earth drives giant loops of air called cells. They explain where the world is wet or dry:
At the Equator hot air rises, cools and releases heavy rain (tropical rainforests). At about 30° N and S that air sinks, warms and dries — creating the world's hot deserts.
The main cells are the Hadley, Ferrel and Polar cells. This circulation, plus ocean currents, moves heat from the Equator towards the poles.
Tropical cyclones
How tropical cyclones form
Tropical cyclones (hurricanes / typhoons) form over warm tropical oceans. The conditions needed are:
Sea-surface temperature above about 26.5 °C, to at least 50 m deep — supplying warm, moist air.
Located roughly 5°–30° from the Equator, so the Coriolis effect can spin the storm (too weak at the Equator itself).
Warm air rises rapidly, creating low pressure; condensation releases huge energy, sucking in more air and strengthening the storm around a calm eye.
Watch out: tropical cyclones need warm ocean, so they weaken once they hit land or cooler seas (their fuel — warm, moist air — is cut off).
Match it
Match the term to its meaning
Tap a term on the left, then tap its correct description on the right.
Quick check
Cyclone conditions
?Which condition is essential for a tropical cyclone to form and strengthen?
Drought
Drought — a slow-onset hazard
A drought is a long period of below-average rainfall causing a water shortage. Its causes include:
High pressure blocking rain-bearing weather systems for weeks or months.
Changes in ocean circulation such as El Niño, which shifts rainfall away from some regions.
Failed monsoon rains in places like the Sahel or parts of Asia.
Impacts: crop failure and famine, dead livestock, water rationing, wildfires, and conflict over scarce water. Climate change is expected to make some droughts more frequent and severe.
Compare: a cyclone is a rapid-onset hazard (hits in hours); a drought is a slow-onset hazard that builds over months.
Number check
Working out the warming
🔢In a year the average temperature was 13.6 °C. A century earlier it had been 12.5 °C. How much has the average temperature risen over that century? (Give the answer in °C.)
°C
Rise = later temperature − earlier temperature.
Sort it
Cyclone or drought?
Tap a feature, then tap the hazard it best describes.
🌀 Tropical cyclone
🌵 Drought
Explain it
Your turn — the greenhouse effect
✎Explain how human activity is enhancing the greenhouse effect and warming the planet. Use the words fossil fuels, greenhouse gases and heat.
Model answer
Burning fossil fuels (coal, oil, gas), plus deforestation and farming, releases extra greenhouse gases such as CO₂ and methane into the atmosphere.
These gases trap more of the outgoing heat (long-wave radiation) that would otherwise escape to space.
This enhanced greenhouse effect raises average global temperatures, causing climate change.
Recap
The key ideas to know
Climate over time: glacials and interglacials in the Quaternary; sharp warming since ~1850.
Natural causes: Milankovitch cycles, solar output, volcanic eruptions.
Human causes: fossil fuels + deforestation → extra greenhouse gases → enhanced greenhouse effect.
Evidence: ice cores, temperature records, shrinking ice, rising seas, tree rings.
Global circulation: rising air at the Equator (rain), sinking air at ~30° (deserts).
Tropical cyclones: need warm ocean (~26.5 °C+), Coriolis spin; low pressure, calm eye; weaken over land.
Drought: slow-onset; caused by high pressure, El Niño, failed monsoon; famine and water shortage.
You've covered the Edexcel B Weather Hazards & Climate Change content. Press Finish to see your score.
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