Climate: Causes and Effects of Climate Change (Our Fragile Planet)
Though climate change is normal in Earth's history, global warming has raised average temperatures to their highest in two millennia, resulting in melting ice caps, shorter winters, changes in the seasonal behaviors of animals, and more extreme weather. And though greenhouse gases are essential for keeping the planet's temperatures comfortable, fossil fuel burning and other human activities are increasing greenhouse gas levels and causing temperatures to rise.
While there are several factors that contribute to global warming, such as natural changes in the Earth's inclination and revolution around the sun, by far the biggest factor is the emission of greenhouse gases. Carbon dioxide, methane, ozone, chlorofluorocarbons, water vapor, and nitrous oxide are added at alarming rates to the atmosphere by daily human activity. Every person on Earth has a 'carbon footprint' - a measure of greenhouse gas contributed to the atmosphere on a daily basis.
