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Early Earth’s atmosphere is inferred from geological evidence and models, with volcanic gases contributing water vapour, carbon dioxide and other gases. Cooling allowed water to condense into oceans. Carbon dioxide became stored in dissolved forms, carbonate rocks and fossil fuels. Photosynthetic organisms released oxygen, gradually altering the atmosphere and enabling different life. Distinguish an evidence-based explanation from a direct measurement of ancient air.
Video by Cognito. The video’s own board label is retained; follow the specification reference and scope notes on this lesson for assessed content.
Viewing focus: Describe atmospheric change over time
After watching, attempt these questions before opening the answers. You can also use the written lesson below.
After watching 1: What radiation does Earth emit that greenhouse gases absorb?
Infrared. This is part of Earth’s energy balance.
After watching 2: Which process increased atmospheric oxygen over geological time?
Photosynthesis. Photosynthesis releases oxygen.
What you'll be able to do
Early Earth’s atmosphere is inferred from geological evidence and models, with volcanic gases contributing water vapour, carbon dioxide and other gases. Cooling allowed water to condense into oceans. Carbon dioxide became stored in dissolved forms, carbonate rocks and fossil fuels. Photosynthetic organisms released oxygen, gradually altering the atmosphere and enabling different life. Distinguish an evidence-based explanation from a direct measurement of ancient air.
Earth absorbs incoming radiation and emits infrared radiation. Greenhouse gases absorb and re-emit some outgoing infrared, affecting the rate at which energy escapes to space. Human activity raises concentrations of gases including carbon dioxide and methane, enhancing this effect. The greenhouse effect is different from depletion of the ozone layer. Climate refers to long-term patterns, so a single unusually cold day does not refute a long-term warming trend.
Carbon monoxide is toxic; sulfur dioxide and nitrogen oxides contribute to respiratory problems and acid rain; particulates affect health and can alter radiation reaching Earth. Carbon footprints estimate greenhouse-gas emissions across an activity’s lifecycle, often using carbon-dioxide equivalents. Their accuracy depends on boundaries and assumptions. Compare mitigation options using emissions saved, energy supply, cost and feasibility, and identify uncertainty instead of treating an incomplete estimate as a precise universal fact.
Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.
Common mistakes to avoid
Key takeaways
Question 1: Why do two carbon-footprint estimates for one product differ?
Compare the included stages and data before judging the numbers.
Check the assessed scope and practical or mathematical requirements.
An external explanation or interactive activity to use alongside the lesson. It may include extension material.
Close the notes and answer from memory. Revisit any explanation you cannot yet reconstruct.
Test yourself
Answer a few questions, then review anything you missed.
Start with the quiz above to check the key ideas. You can also choose another topic from the practice library.