The greenhouse effect is a natural process that warms the Earth's surface. When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases.
Coal burned in power stations contains carbon which combines with oxygen in the atmosphere to form carbon dioxide. The man-made (or anthropogenic) component of the greenhouse effect is caused by man's activities that emit greenhouse gases to the atmosphere. The most important of these is the burning of fossil fuels