The Climate System Lab
Warm air, cold air and a spinning planet decide where deserts and rainforests sit. See how the atmosphere moves heat, and how we know the climate is changing.
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The Climate System Lab 🌍
Why is the equator drenched in rainforest while deserts ring the planet at 30 degrees? The answer is the way the atmosphere moves **heat** around the globe. This module explains that circulation, then looks at how the climate has changed, both naturally and because of us.
Global atmospheric circulation 🌀
The sun heats the Earth most strongly at the **equator**. There: - Warm air **rises**, creating **low pressure**, clouds and **heavy rain** (the wet tropics). - High up, the air flows towards the poles, cools, and **sinks** at about **30 degrees**, creating **high pressure** and dry, clear skies (**hot deserts**). This giant loop of rising and sinking air is called a **Hadley cell**.
Label the circulation
An interactive activity.
Where deserts sit
Why are many of the world's hot deserts found at about 30 degrees north and south of the equator?
- Air that rose at the equator sinks there, giving high pressure and dry, clear conditions
- The sun never reaches those latitudes
- Air rises there, causing heavy rain
- They are always covered in ice
One Hadley cell
An interactive activity.
Natural climate change 🌋
Climate has always changed for **natural** reasons, long before humans: - **Asteroid impacts** throw up dust that blocks the sun. - **Orbital variations** (Milankovitch cycles): slow changes in Earth's orbit and tilt. - **Volcanism**: big eruptions release ash and gases that cool the planet. We know about past climates from **ice cores**, **tree rings** and **historical sources**.
Match each source of evidence to what it records
- Ice cores
- Tree rings
- Historical sources
- Trapped air bubbles revealing past carbon dioxide and temperature
- Ring width each year showing how good the growing conditions were
- Written records such as diaries, paintings and harvest dates
Human-caused change 🏭
Recent, rapid warming is mainly **human-caused**. Burning fossil fuels, deforestation and farming release **greenhouse gases** (carbon dioxide and methane), which trap more heat. The evidence includes rising carbon dioxide levels, rising global temperatures, rising sea levels and retreating glaciers. Future projections are **uncertain**, because they depend on how much we keep emitting.
Natural or human?
Select ALL THREE NATURAL causes of climate change.
- Asteroid impacts
- Changes in Earth's orbit and tilt
- Major volcanic eruptions
- Burning fossil fuels
- Deforestation by people
- Farming livestock
Climate summary
At the equator the sun heats the air, which _____, giving low pressure and heavy rain. That air sinks again at about 30 degrees, giving _____ pressure and hot deserts; this loop is the _____ cell. Natural climate change has causes like volcanism, but recent rapid warming is mainly _____-caused by greenhouse gases.