Energy from the sun drives the earth's weather and climate. Incoming rays heat the earth's surface, radiating heat energy back into space. Atmospheric "greenhouse" gases trap some of the outgoing energy. Problems arise when the concentration of greenhouse gases increases beyond normal levels, thus retaining excessive heat somewhat like a car with its windows closed in the summer. As the earth warms, the consequences are expected to affect both humans and ecosystems. The Industrial Revolution, greenhouse gas emissions have increased, considerably enhancing the heat-trapping capability of the earth's atmosphere. Global environmental problems can result in very different effects on countries that will sit around the negotiating table. While low-lying countries could be completely submerged by the sea level rise predicted by some climate change models, arid nations could see their marginal agricultural lands succumb to desertification. The chapter also presents an overview of key concepts discussed in this book.