What exactly are greenhouse gases and the greenhouse effect? -Andres, 10, Bolivia 

Dear Andres,

If it weren’t for greenhouse gases, Earth would be an extremely cold, deserted planet. Plants couldn’t grow and animals like us wouldn’t be able to survive.

dru-hero-poseGreenhouse gases, like all gases, are made up of molecules. Air, for example, is a gas made of mostly nitrogen and oxygen molecules. We breathe those molecules all the time. They fill up our lungs and help us burp.

When I visited my friend Brian Lamb, an engineer at Washington State University, he told me there are a few things that set greenhouse gases apart from other kinds of gases.

Greenhouse gases are named after greenhouses, the glass buildings where humans often grow fruits, vegetables, and flowers when it’s too cold to plant them outside. Greenhouses can trap a lot of heat.

Our planet is kind of like a greenhouse, too. Just as light from the Sun travels through the glass of a greenhouse, light also travels through Earth’s atmosphere, the mass of air that surrounds the planet.

When gas molecules absorb light or energy, they warm up and can also re-emit this energy back to the earth’s surface. Greenhouse gases trap heat, or energy, and keep it in the Earth system so that the Earth and atmosphere become warmer.

Greenhouse gases absorb what scientists call infrared radiation. That’s the fancy word for the same kind of heat we feel coming from a kitchen stovetop. It’s also the kind of heat that makes pavement feel hot enough to fry an egg on a hot summer day.

Lamb explained that greenhouse gases are also different from other gases because they stay in the atmosphere for hundreds, even thousands of years. Some greenhouse gases will even heat up the Earth for up to 25,000 years. But how long they stay also depends on which greenhouse gas you’re talking about.

The main greenhouse gases we know about in our atmosphere include carbon dioxide, water vapor, methane, nitrous oxide, and ozone.

While some greenhouse gases form naturally, humans are adding extra greenhouse gases to the atmosphere. Carbon dioxide is the big one. It comes from sources like cars, trucks, and factories that are burning fossil fuels.

Greenhouse gases, particularly carbon dioxide, are also being added to the Earth faster than the planet has typically been able to process them. There are simple things humans can do every day to reduce the amount of carbon dioxide in the atmosphere. They can use less electricity, turn lights and computers off, and walk or ride bikes instead of driving cars whenever possible.

“We know that carbon dioxide levels are increasing. We know that carbon dioxide absorbs infrared radiation,” Lamb says. “That tells us we should be looking for a greenhouse effect.”

The greenhouse effect is the overall warming up of the planet as these greenhouse gases trap heat.

No matter where greenhouse gases are released, they’ll mix in with other molecules throughout the atmosphere. In this way, greenhouse gases impact the whole planet.

Sincerely,
Dr. Universe