--- title: "Earth's Atmosphere & CO2" description: "Describe the composition of Earth's atmosphere (mainly nitrogen and oxygen, with small amounts of CO₂ and other gases), explain how human activity increases CO₂, and describe the impact on global clim" canonical: https://lightmysky.com/learn/science/earths-atmosphere-and-co2-mt_mTpV-0rtkO source: https://lightmysky.com/learn/science/earths-atmosphere-and-co2-mt_mTpV-0rtkO.md retrieved: 2026-10-19 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Earth's Atmosphere & CO2 Describe the composition of Earth's atmosphere (mainly nitrogen and oxygen, with small amounts of CO₂ and other gases), explain how human activity increases CO₂, and describe the impact on global climate Subject: Science · Area: Matter & Materials · Ages 12 to 14 Page: https://lightmysky.com/learn/science/earths-atmosphere-and-co2-mt_mTpV-0rtkO ## Ready when they can - States the approximate percentages of nitrogen, oxygen, CO₂, and argon in the atmosphere - Explains how burning fossil fuels and deforestation increase atmospheric CO₂ - Describes the greenhouse effect and how it leads to climate change - Discusses one specific consequence of climate change (e.g. rising sea levels, extreme weather) ## Lesson: Earth's Atmosphere and Rising CO2 Earth's atmosphere is the layer of gas wrapped around the planet, held in place by gravity. It looks empty, but it's a mix of several gases. Two of them make up almost all of it: nitrogen and oxygen. *(drawing: Nitrogen and oxygen make up 99 out of every 100 parts of air. Argon is next, and CO2 is such a small sliver you can barely see its bar.)* About 78% of the air is nitrogen and about 21% is oxygen, the gas your body needs to survive. The last 1% is a mix of other gases. Almost all of that sliver is argon, and only a tiny part of it, about 0.04%, is carbon dioxide (CO2). **Example.** CO2 is less than half of that leftover sliver, yet it plays a huge part in keeping Earth warm. You already know CO2 traps heat near Earth's surface, the greenhouse effect. When people burn coal, oil, and gas for energy, and when they cut down forests that would otherwise soak up CO2, they add more of this gas to the air. More CO2 traps more heat, and Earth's average temperature climbs. That's climate change, and it's already causing sea levels to rise as ice melts and warmer water expands. **Tip.** A gas doesn't need a big share of the air to matter. CO2 is a tiny slice of the atmosphere, but even small increases trap enough extra heat to shift climate patterns worldwide. **Recap.** Air is mostly nitrogen and oxygen, but burning fuel and clearing forests keeps adding CO2, and that tiny gas is enough to trap extra heat and warm the whole planet. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [The Carbon Cycle](https://lightmysky.com/learn/science/the-carbon-cycle-mt_Be1A88GUpu) - [Greenhouse Gas Science](https://lightmysky.com/learn/science/greenhouse-gas-science-mt_EQQWKz03P8) - [How Earth systems interact](https://lightmysky.com/learn/science/how-earth-systems-interact-mt_LKagN9GJPX) ## Opens up - [Finite Resources & Recycling](https://lightmysky.com/learn/science/finite-resources-and-recycling-mt_0e5rZxbAeR) - [The Layered Atmosphere and Why Temperature Reverses With Height](https://lightmysky.com/learn/science/the-layered-atmosphere-and-why-temperature-reverses-with-height-mt_2icQ747JhN) - [Pollutants from Burning Fuels](https://lightmysky.com/learn/science/pollutants-from-burning-fuels-mt_DDiyDBy6YW) - [Renewable vs non-renewable energy](https://lightmysky.com/learn/science/renewable-vs-non-renewable-energy-mt_w2A8D76ymp)