1. Whatever happened to the dinosaurs?

The dinosaurs are in your gas tank!

The dinosaurs contained carbon. You contain carbon. All living things on Earth contain carbon. Lots of it. If you weigh 100 pounds, 18 pounds of you is pure carbon! Plants are almost half carbon!

You are 18 percent carbon. Plants are 45 percent carbon.

An atom is the tiniest possible particle of any element, like carbon or oxygen. A carbon atom combines easily with two oxygen atoms to make the compound carbon dioxide.

"C" stands for carbon, "O" stands for oxygen, so carbon dioxide is often called "C-O-2, and written "CO2." CO2 is a gas. It is invisible. CO2 is really important.

Read on to learn why.

2. How does the carbon get into living things?

Carbon dioxide in, water and oxygen out.

Plants take in CO2. They keep the carbon and give away the oxygen. Animals breathe in the oxygen and breathe out carbon dioxide.

For hundreds of millions of years, dead plants and animals were buried under water and dirt. Heat and pressure turned the dead plants and animals into oil, coal, and natural gas.

Plants and animals depend on each other. It works out well. For hundreds of millions of years, plants and animals have lived and died. Their remains have gotten buried deep beneath Earth's surface. So for hundreds of millions of years, this material has been getting squished and cooked by lots of pressure and heat.

Oil shoots out of the ground when a well is dug. Coal is mostly carbon from long-dead plants. Natural gas from pockets deep under ground shoots out when released, sometimes with oil. Sometimes oil companies release and burn the gas to relieve pressure in their equipment.

So what happens to all this dead plant and animal stuff? It turns into what we call fossil fuels: oil, coal, and natural gas. This is the stuff we now use to energize our world. We burn these carbon-rich materials in cars, trucks, planes, trains, power plants, heaters, speed boats, barbecues, and a zillion other ways.

3. How does the carbon get out of living things?

When fossil fuels burn, we mostly get three things: heat, water, and CO2. We also get some solid forms of carbon, like soot and grease.

A very smoggy day in the big city.

So that's where all the old carbon goes. All that carbon stored in all those plants and animals--including the dinosaurs--over hundreds of millions of years is getting pumped back into the atmosphere over just one or two hundred years.

4. Is carbon in the air good, bad, or just ugly??

A greenhouse traps the Sun's energy inside and keeps the plants warm.

Here's the big, important thing about CO2: It's a greenhouse gas. That means CO2 in the atmosphere works to trap heat close to Earth. It helps Earth to hold on to some of the energy it gets from the Sun so the energy doesn't all leak back out into space.

If not for the greenhouse effect, Earth would be an ice ball.

If it weren't for this greenhouse effect, Earth's oceans would be frozen solid. Earth would not be the beautiful blue and green planet of life that it is.

So, CO2 and other greenhouse gases are good--up to a point. But CO2 is so good at holding in heat from the Sun, that even a small increase in CO2 in the atmosphere can cause Earth to get even warmer.

This graph shows how temperature and carbon dioxide have increased and decreased together over the past 400,000 years.

Ref: http://www.epa.gov/climatechange/science/pastcc_fig1.html.

Check out the Climate Time Machine to see how CO2 and temperature have changed together through history.