Most of Earth’s atmosphere is composed of

• oxygen and hydrogen.

• hydrogen and nitrogen.

• nitrogen and oxygen.

• carbon and ozone.

Ozone in Earth’s atmosphere is important because it

• causes rain to fall.

• absorbs harmful

  radiation.

• absorbs harmful

  pollution.

• helps clouds form

Water vapor in the atmosphere is the source of

• clouds and rain.

• pollution.

• carbon dioxide.

• wind.

Current, short-term variations in the atmosphere are referred to as ____.

• humidity

• lapse rate

• weather

• the ionosphere

Polar and tropical regions maintain fairly constant average temperatures because

• the Sun always strikes these regions at the same angle.

• air masses remain stationary near the poles and equator.

• Earth radiates extra energy back into space.

• the continual motion of air and water reallocates heat energy throughout Earth.

The Coriolis effect is due to the ____ of Earth.

• revolution

• rotation

• shape

• density

A lowering of global temperatures caused by dust blocking solar radiation can be triggered by

• blizzards.

• El Niño.

• hurricanes.

• volcanic eruptions.

Most scientists agree that global warming is occurring, but they mainly disagree about

• how much has occurred.

• whether there are

  greenhouse gases.

• what global warming

  really is.

• what is causing it.

Scientists hypothesize that an increase in atmospheric carbon dioxide leads to an increase in Earth’s absorption of

• solar radiation.

• water vapor.

• gamma rays.

• volcanic ash.

Climatic changes may be triggered by changes in Earth’s axis and

• orbit.

• continents.

• circumference.

• density.