Quiz: What You Don’t Know About Greenhouse Gases


Emissions from manufacturing in Toronto (Credit: Kibae Park/United Nations)

UN climate talks often focus on “carbon” pollution as they set guidelines to curb global warming. Yet carbon dioxide, emitted through the burning of fossil fuels, is not the only greenhouse gas that contributes to human-made climate change. So how much do you really know about these gases?

Quiz by Wendy Koch

True or False: The extent that a greenhouse gas warms the Earth depends on the length of time it remains in the atmosphere and its ability to absorb energy.

  • True
  • False

True. Scientists use these factors to calculate a gas’s global warming potential, which measures how much heat it absorbs per pound.

Which greenhouse gas has the highest global warming potential?

  • Carbon dioxide
  • Methane
  • Nitrous oxide
  • Sulfur hexafluoride

This fluorinated gas absorbs the most heat over a hundred-year period. Its global warming potential is 23,500, compared to 28 for methane and 1 for carbon dioxide.

What is the largest source of U.S. greenhouse gas emissions?

  • Agriculture
  • Transportation
  • Electricity production
  • Home heating

Electricity production accounted for 31 percent of U.S. greenhouse gas emissions in 2013, followed by transportation at 27 percent.

Energy-related CO2 accounts for approximately what share of total U.S. human-made greenhouse gases?

  • 20 percent
  • 40 percent
  • 60 percent
  • 80 percent

These emissions—mostly from burning coal, oil, and natural gas—accounted for 82 percent of all U.S. greenhouse gases in 2013.

After CO2, which greenhouse gas accounts for the next largest share?

  • Sulfur dioxide
  • Methane
  • Nitrous oxide
  • Hydrofluorocarbons

Methane—emitted from landfills, coal mines, oil/gas operations, and agricultural livestock—accounted for 10 percent of U.S. greenhouse gas emissions.

How long does methane stay in the atmosphere?

  • 1 month
  • 1 year
  • 6 years
  • 12 years

On average, methane lingers in the atmosphere for 12 years, while CO2 can remain for thousands of years.

True or false: Water vapor is a greenhouse gas.

  • True
  • False

True. It’s one of the naturally occurring gases, along with carbon dioxide, methane, and nitrous oxide. Others are synthetic, including chlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride.

What can remove carbon dioxide from the atmosphere?

  • Vegetation
  • Oceans
  • Carbon capture equipment
  • All of the above

Vegetation and the oceans absorb some—but not all—CO2 emissions. Power plants can use carbon capture and sequestration technology to reduce emissions.

The United States and other countries are trying to stop the rising emissions of hydrofluorocarbons. Where are HFCs most commonly used?

  • Boats
  • Food
  • Refrigerators
  • Books

HFCs are coolants used in air conditioners and refrigerators that have a high global warming potential of about 10,000. (Learn more about how your fridge is changing as a result.)

U.S. carbon emissions rose slightly in 2014 for the second consecutive year after declining for several years. What’s the biggest reason for this uptick?

  • Increased use of natural gas
  • Economic growth
  • Slowdown in decline in coal
  • Decreased production of nuclear power

Economic growth was the biggest reason, though coal’s slowing decline was a lesser contributor. Natural gas emits half as much CO2 as coal when burned, so it lowers emissions when used instead of coal. Generation of nuclear power, which emits almost no CO2, increased slightly in the last two years.





Super job. Your knowledge is stratospheric.

Way to go! Keep building your knowledge, and take the quiz again to boost your score.

We know you can do better. See if a second try brings the answers to light.

Brush up on your facts at the Energy & You, and then retake the quiz to see how much you’ve learned.

Retake Quiz

More Energy Quizzes

See all quizzes »

@NatGeoEnergy on Twitter