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Hot Topic

Everyone seems to be talking—or singing, or making a movie—about global warming.
But despite rising awareness, misconceptions abound about what scientists prefer to call climate change.
Take our pop quiz and find out how much you really know.
Answers are at the end of the article.



True Or False (1-12)

1. The concentration of carbon dioxide in the atmosphere today is 35 percent higher than at the start of the Industrial Revolution, around 1750.

2. Eleven of the 12 years from 1995 to 2006 were among the 12 warmest since instrument records began, in 1850.

3. Ocean life is shielded from the effects of carbon dioxide buildup and climate change.

4. China currently contributes the most carbon dioxide to the atmosphere.

5. Earth has been warmer in the past.

6. Some kinds of particulate pollution in the atmosphere counteract global warming by reducing the solar radiation that reaches Earth's surface.

7. No place on Earth is, on average, colder today than it was 100 years ago.

8. Natural phenomena, including volcanic eruptions, trap heat close to the surface of Earth and are a major cause of global warming.

9. Scientists derive evidence of the composition of Earth's atmosphere hundreds of thousands of years ago from air bubbles in ancient ice.

10. Livestock is a significant contributor of greenhouse gases.

11. As average global temperature rises, average precipitation increases.

12. Biofuels like ethanol (which is made from corn) and biodiesel (which is mostly from soybeans) can help reduce greenhouse gas emissions.

Multiple Choice (13-16)

13. By how much do scientists estimate that the global sea level rose in the 20th century?

a. zero
b. 6-9 inches
c. 3-4 feet
d. 21-23 feet

14. By how much do scientists estimate the global sea level would rise if all of Greenland's glacial ice melted?

a. zero
b. 6-9 inches
c. 3-4 feet
d. 21-23 feet

15. Which two of the following are not heat-trapping gases?

a. carbon dioxide
b. nitrogen
c. water vapor
d. ozone
e. oxygen

16. Since 1961, the oceans have absorbed what percentage of the heat that has been added to the climate system?

a. 50 percent
b. 20 percent
c. 80 percent
d. 15 percent

The questions and answers are from David A. McConnell and David N. Steer, professors of geology at the University of Akron, in Ohio; Martin Ruzek of Earth System Science Education for the 21st Century, which is sponsored by NASA; and Debbie Zmarzly, a scientist at the Birch Aquarium in La Jolla, Calif.

Answers and explanations to the questions

True Or False

1. True: Carbon dioxide levels before the Industrial Revolution were about 280 parts per million; the concentration today is 380 parts per million.
2. True
3. False: Increases in ocean temperatures may already be harming marine species, particularly corals. Some marine life could shift or expand in range. As the oceans absorb excess carbon dioxide, they become more acidic, affecting the shell-making ability of species from tiny plankton to giant clams.
4. False: The U.S. contributes the most, but China, which is building many more coal-fired power plants, could move into the top spot within a year or two.
5. True: Evidence suggests temperatures during past interglacial periods sometimes exceeded today's averages, in some cases for at least several thousand years.
6. True: Some kinds of particle pollution such as dust and ash reflect and scatter sunlight, reducing the amount of solar energy reaching Earth. This phenomenon, known as global dimming, may have masked global warming by as much as 50 percent. But these particles also cause serious health problems, and as more countries (particularly developing nations like China and India) address pollution problems, the true impact of global warming will be revealed.
7. False: In a few locations, including parts of Bolivia, Nigeria, and the Southeastern U.S., temperatures decreased during the 20th century.
8. False: Many natural processes influence climate, but most climate scientists have concluded that the buildup of human-generated emissions is responsible for the pronounced warming trend measured since 1950.
9. True: Cores drilled from ice sheets in polar regions contain air bubbles that are samples of the atmosphere at the time the ice formed.
10. True: Ruminant livestock (such as cows or sheep raised for meat or dairy) have a complex digestive process that emits methane gas as a byproduct. They contribute 28 percent of methane emissions that come from human-related activities.
11. True: Higher temperatures lead to more active evaporation and more rain and snow. Overall, higher latitudes (places farther from the equator) are likely to see more precipitation, and areas near the equator less. Changing circulation patterns may also lead to precipitation declines in some areas.
12. True: But only if biofuels, which are derived from farm-grown products like corn or soybeans, are produced without using large amounts of fossil fuels. Making biofuels can consume almost as much energy as the resulting products—ethanol and biodiesel—contain. Ethanol and biodiesel also release carbon dioxide, but they are renewable energy sources and burn more cleanly than fossil fuels.

Multiple Choice

13. b
14. d
15. b and e: Nitrogen and oxygen, which make up 99 percent of Earth's atmosphere, allow infrared radiation (heat) to pass through.
16. c