Climates are the prevalent, long term atmospheric conditions. The atmosphere consists primarily of nitrogen and oxygen. Small amounts of human-induced atmospheric pollutants can spread and ruin protective atmospheric layers, harm animals and people, and cause the earth to become warmer. Warming gases—carbon dioxide, methane, and others--are “greenhouse gases” and fossil fuel burning emits most of them. Carbon dioxide also comes from forest land clearing for agriculture, to a lesser extent and with quicker reversibility. Solar energy heats the earth in intricate ways. Some solar wavelengths are reflected or absorbed in the atmosphere. Others reach the earth and are reflected back into space or to the clouds, where energy is absorbed or again relected. Other solar energy heats the land, which heats the air, causing the air to rise and initiate wind patterns. Solar energy can heat water, evaporating some and causing it to move into the air and travel with the wind. Heated water can also move the energy through currents. The result is a complex system of recirculating energy to the Earth. Mountains and other features cause the energy and water to move in predictable ways.