ELI5: What is carbon dioxide (CO2)?

Imagine you're blowing out birthday candles! The invisible stuff you breathe out is mostly carbon dioxide (CO2). It's a gas, like the air around us, but different.

Think about when you run around and play. You breathe faster, right? That's because your body is working hard, burning the food you ate for energy. When your body burns that food, it makes CO2 as a waste product, just like how a car makes smoke (exhaust) when it burns gasoline. You breathe out that CO2.

Plants are like the opposite of us! They "breathe in" CO2 from the air. They use sunlight, water, and the CO2 to make their own food (sugar) in a process called photosynthesis. As a bonus, they release oxygen for us to breathe! It's a perfect swap.

But there's a problem. When we burn things like wood, gasoline in cars, or coal in power plants, we create lots of CO2. Too much CO2 in the air is like putting a thicker blanket on the Earth. This thicker blanket traps heat, which makes the Earth warmer. This is called global warming or climate change.

So, what can we do?

• Walk or bike instead of driving sometimes.
• Turn off the lights when you leave a room.
• Plant trees!
• Help your family save energy at home.