Earth's Atmosphere and Rising CO2

Science · Matter & Materials · ages 12-14

Name ______________________ Date ____________

About what percent of the air is CO2?
- 4%
- 0.04%
- 21%
Which two gases make up almost all of Earth's atmosphere?
- Nitrogen and oxygen
- Oxygen and carbon dioxide
- Nitrogen and argon
Argon makes up a smaller percentage of the atmosphere than carbon dioxide.
Circle one: True False
Why does cutting down a forest add to atmospheric CO2, even though nothing is burned?
- Fewer trees means less CO2 is being absorbed from the air
- Trees release CO2 only when they are cut down
- Forests produce oxygen but never absorb CO2
Which of these human activities adds CO2 to the atmosphere?
- Planting a new forest
- Recycling glass bottles
- Burning coal in a power plant
How does extra CO2 in the atmosphere lead to a warmer planet?
- It blocks sunlight from reaching the ground
- It traps more heat near Earth's surface
- It replaces the oxygen that keeps Earth cool
Which of these is a real, observed consequence of rising global temperatures?
- Rising sea levels as ice melts and ocean water expands
- A steady decrease in rainfall everywhere on Earth
- A permanent drop in ocean salt levels
A student says: 'Since CO2 is under 1% of the air, adding more of it can't really change the climate.' What's the flaw in this reasoning?
- CO2 is actually over 50% of the air
- The greenhouse effect only works with oxygen
- A small gas can still trap a large amount of heat

Answer key

For grown-ups. Fold this page away before handing over the rest.

0.04% · CO2 is a tiny sliver of the air, about 0.04%, even though it has a big effect on temperature.
Nitrogen and oxygen · Nitrogen is about 78% and oxygen about 21% of the air. Together, that's almost all of it.
False · It's the other way around. Argon is about 0.9% of the air, while CO2 is only about 0.04%.
Fewer trees means less CO2 is being absorbed from the air · Living trees pull CO2 out of the air as they grow. Remove the trees, and that CO2 stays in the atmosphere instead.
Burning coal in a power plant · Burning fossil fuels like coal releases carbon that was stored underground back into the air as CO2.
It traps more heat near Earth's surface · CO2 lets sunlight in but traps heat trying to escape, the greenhouse effect. More CO2 means more heat gets trapped.
Rising sea levels as ice melts and ocean water expands · As glaciers and ice sheets melt and warmer water expands, sea levels rise. This is already affecting coastal communities.
A small gas can still trap a large amount of heat · Percentage share doesn't determine impact. CO2 traps heat efficiently, so even a small increase changes how much heat stays near Earth's surface.