What are the causes of climate change?
Climate change is caused by an alteration of the chemical composition of Earth’s atmosphere by various activities of humankind. The physical mechanism depends on making it more difficult for infrared radiation from Earth to escape to space. A few percent of the incoming solar energy arrives as invisible ultraviolet radiation, with about half of the rest in the visible (violet to red) and the remainder as infrared radiation, also invisible. The cooler an object, the less energy it gives off and the peak wavelengths shift from violet to yellow (the sun) to red, and then to infrared. Because the surface temperature of the Earth is much cooler than the sun, the energy escaping from the Earth is emitted at much longer wavelengths (the “far infrared”). However, some of these wavelengths can be strongly absorbed by atmospheric molecules which contain three or more atoms, such as carbon dioxide, methane, water vapor, ozone, nitrous oxide and the chlorofluorocarbons (CFCs). (The less complex ma
