Global warming is the increase in amounts of greenhouse gases in Earth's atmosphere
Greenhouse gases trap the sun's rays in the atmosphere, raising the temperature to abnormal levels
The main greenhouse gases are carbon dioxide, water vapor, methane, and ozone
Greenhouse gases are caused by natural gases and other common sources of energy, as they are released when those sources are burned
The 1990s were the warmest decades since the thermometer was used to measure temperature.
2006 was the warmest year on record for the U.S. according to some sources. Others say it was 2005, 2007, or 1998.
In the last 1,000 years, the temperature increase in the 20th century has been the largest.
Over 400,000 square miles of Arctic sea ice have melted.
In 2005, over $100 billion dollars in damage was caused by hurricanes hitting the U.S. coast.
using our reader.