Burning coal, oil and natural gas adds CO2 to the air.

Circle one:   True   False

How do greenhouse gases help warm Earth's surface?

• They slow the loss of heat to space.
• They stop most sunlight before it reaches the surface.
• They make the Sun send more energy toward Earth.

Which change can result from a warming climate?

• Glaciers grow because warmer air freezes more water.
• More glacier ice melts on land.
• Glaciers stay unchanged because land ice cannot melt.

With other conditions unchanged, what would much less greenhouse warming do to Earth's average temperature?

• It would rise because more heat could escape into space.
• It would stay the same because sunlight is the only factor.
• It would fall because heat could escape faster.

These made-up school plans cut yearly CO2 emissions by 12 kg and 17 kg. How many kg greater is Plan B's cut than Plan A's?

Answer: ______________

Why can warming seawater raise sea level even without extra meltwater?

• Warmer seawater takes up more space.
• Warming creates new water molecules in the ocean.
• Warm water weighs more and pulls the surface upward.

A mountain town has warmer winters and earlier snowmelt. Heavy spring rain then falls while snow is melting. How can rain and snowmelt together affect river flooding?

• Only rainfall matters; snowmelt adds no water to rivers.
• Only snowmelt matters; rain adds no water to rivers.
• Rain and snowmelt can combine to raise flood risk.

Ravi says cars are the only fossil-fuel CO2 source, so replacing car trips with walking would stop all these emissions. Which fact limits his claim?

• Walking can reduce emissions only when every car stops.
• Factories and power plants burn fuels too.
• Cars release CO2, but burning fuel for electricity does not.