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The atmosphere and climate change
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Earth's atmosphere has changed dramatically over billions of years, and human activity is changing it now.
The early atmosphere
Volcanoes released mainly carbon dioxide, water vapour and small amounts of other gases. There was little or no oxygen.
Water vapour condensed to form the oceans, which dissolved carbon dioxide.
Water vapour condensed to form the oceans, which dissolved carbon dioxide.
Oxygen arrives
Algae and plants photosynthesised, removing carbon dioxide and releasing oxygen.
Test for oxygen: it relights a glowing splint.
Today: about 78% nitrogen, 21% oxygen, 0.9% argon, 0.04% carbon dioxide.
Test for oxygen: it relights a glowing splint.
Today: about 78% nitrogen, 21% oxygen, 0.9% argon, 0.04% carbon dioxide.
The greenhouse effect
Greenhouse gases (carbon dioxide, methane, water vapour) absorb heat radiated from the Earth, keeping it warm.
Human activity, such as burning fossil fuels and farming, adds more, causing global warming and climate change.
Human activity, such as burning fossil fuels and farming, adds more, causing global warming and climate change.
How did the amount of carbon dioxide in the early atmosphere decrease?
- It dissolved in the oceans.
- Plants and algae used it in photosynthesis.
- Some was locked into rocks and fossil fuels.
Answer: Oceans, photosynthesis and sedimentary rocks.
Early atmosphere: mostly CO2 from volcanoes. Oceans and photosynthesis reduced CO2 and added O2. Today: 78% N2, 21% O2. Extra greenhouse gases from humans cause climate change.
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