Molecular models of assorted greenhouse gases, including carbon dioxide (right, with double bonds), methane (top, centre), water (top, left) & several unidentified chlorofluorocarbons (CFCs). The build-up of these gases in the Earth's atmosphere traps an increased amount of solar radiation & leads to a gradual warming of the whole planet. The gases are generated by industry, the burning of fossil fuels, modern agricultural methods & deforestation. Global warming is expected to cause massive changes in weather patterns & a rise in sea level, due to polar ice melting, that could flood coastal regions.