In the Arctic, the summer ice is melting, making it hard for polar bears and their cubs to survive. Why is the world getting warmer? The heat of the sun is trapped by the "greenhouse" gases that surround Earth-carbon dioxide, methane, nitrous oxide, and water vapor. If there is just the right amount of these trapped gases, the air is warm enough for plants, animals, and people to thrive. But, now there is too much greenhouse gas, especially carbon...

Describes the positive and negative effects of greenhouse gases on the Earth, and discusses the role of carbon dioxide and other gases, possible conditions if the climate becomes warmer, and how scientists learn about past changes.

"We live in an energy-rich age, in which we can turn on a light with the flick of a switch or drive anywhere by turning a key. But, our vehicles, factories, and power stations, which create the electricity needed to light and heat our buildings, pump carbon dioxide into Earth's atmosphere. Carbon dioxide overload from these human activities is making our planet hotter and hotter--and is causing the Earth's climate to change. Find out what scientists...

Nitrogen, oxygen, argon, and carbon dioxide are all gases in Earth's atmosphere. But what happens when there is too much or two little of a certain gas? Readers will learn how every day activities such as driving, heating buildings, and using aerosols release harmful gases into the air and how it affects the air we breathe. Meets Next Generation Science Standards.