Earth is the only planet in the solar system that is capable of supporting advanced life. Its unique combination of liquid water, a rich oxygen- and nitrogen-based atmosphere, and dynamic weather patterns provide the basic elements for a diverse distribution of plant and animal life.
Over millions of years, landforms and oceans have been constantly changing, mountains have been raised up and eroded away, and continental plates have drifted across Earth. The atmosphere acts like a blanket, evening out temperature extremes and keeping warmth in. Without this" greenhouse effect," Earth would be about 60°F (33°C) cooler on average.
Over the last few decades, scientists have measured a gradual increase in
Earth's temperature. Glaciers and
polar ice caps have begun to shrink. It
is feared that
human activity is causing this rapid change by
increasing
the amount of carbon dioxide and
other "greenhouse gases" in the atmosphere.