Carbon dioxide, or CO2, is the main greenhouse gas in climate change. So how does CO2 get into our atmosphere? Well, carbon is part of a cycle. It starts with the sun, which heats the Earth s surface with more energy in one hour than the whole world uses in a year. Plants, which are kind of like biological chefs, take that sunlight, and then suck in some CO2 from the air, mix them together, and BAM! They create a stored form of energy, in the form of carbohydrates such as glucose and sucrose. The process is called photosynthesis. When animals like us eat those plants our stomachs convert that food back into energy for our own growth. Greenhouse gases are a byproduct of this process, and are released through waste. If those plants die, they decompose, and tiny microorganisms break down those carbohydrates and again, release greenhouse gases as a byproduct. As you see, energy originates from the sun. It is then transferred as it moves through the food chain. But sometimes, carbon based organisms like plants or animals get stuck in the earth. When this happens, they’re compressed under tons of pressure, and turned into carbon-based fossil fuels like oil, coal or natural gas.