Warm Up

Test your knowledge of global temperature change and its impact on Earth's climate.

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1. CHILL OUT

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

Although most locations on the planet have recorded increased temperatures since 1900, changes in global ocean and atmospheric circulation patterns have created small-scale temperature decreases in a few local regions.
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2. FULL OF HOT AIR

Which of the following gases does not trap heat?

Heat-trapping greenhouse gases absorb and emit radiation within the thermal infrared range. Water vapor, carbon dioxide and methane are Earth's most abundant greenhouse gases. Nitrogen, which makes up 80 percent of Earth's atmosphere, is not a greenhouse gas. This is because its molecules, which contain two atoms of the same element (nitrogen), are unaffected by infrared light.
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3. IN HOT WATER

As average global temperature rises,

Higher temperatures give rise to a more active water cycle, which means faster and greater evaporation and precipitation and more extreme weather events.
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4. MUY CALIENTE

Where have some of the strongest and earliest impacts of global warming occurred?

Some of the fastest-warming regions on the planet include Alaska, Greenland and Siberia. These Arctic environments are highly sensitive to even small temperature increases, which can melt sea ice, ice sheets and permafrost, and lead to changes in Earth's reflectance ("albedo").
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5. HOLD THE LINE

Compared to other greenhouse gases, carbon dioxide is the most effective at trapping heat near the Earth's surface.

Water vapor actually has more heat-trapping power than carbon dioxide. It is also more abundant. But carbon dioxide and water vapor interact in crucial ways: More carbon dioxide means the atmosphere gets warmer, which then creates more water vapor, which traps heat and warms the atmosphere even more.
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6. SMOG STORY

Some kinds of pollution in the atmosphere can act to cool the planet by reducing the amount of solar radiation that reaches Earth's surface.

Air pollution can take the form of fine particles called "aerosols," which both absorb and scatter the sun's radiation. Both natural and man-made aerosols, such as dust, sea salt, soot and sulfates, affect the climate by reflecting radiation that is transmitted through the atmosphere.
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7. DOG DAYS

Earth has been warmer in the past than it is today.

Global temperatures during some of the past interglacial periods have exceeded the average temperatures we observe today, although you would have to go back more than three million years to find a period that was clearly warmer than today. Temperatures in the most recent decade have now exceeded the warmth of the previous Eemian interglacial.
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8. WARM AND COZY

If you removed the atmosphere's natural greenhouse effect, and everything else stayed the same, Earth's temperature would be:

The greenhouse effect is a naturally occurring physical process that warms the Earth's surface with energy from the atmosphere. Without the effect, Earth's average surface temperature would be well below freezing.
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9. WATCHING THE EARTH

How do scientists collect evidence about climate?

For the past few decades, scientists have had the benefit of global satellite data. We have accurate ground-based measurements that reach back just over a century. "Proxy" methods, such as tree ring and ice core analysis, are used to reconstruct climate records before the rise of modern instruments.