This document discusses global warming and climate change. It provides background on Earth's climate history and the greenhouse effect. It notes that Earth has gone through natural warming and cooling cycles in the past. However, human activity is now the dominant cause of increased carbon dioxide and methane in the atmosphere. The United States emits a large amount of greenhouse gases annually from sources like transportation, home energy use, and electricity generation. Small individual actions like changing light bulbs and driving less can collectively make a significant impact on reducing emissions and slowing global warming. The document encourages readers to evaluate their daily habits and make simple lifestyle changes to reduce their carbon footprint.