As such, the greenhouse effect is a natural phenomenon which protects the planet against heat loss. Water vapour, carbon dioxide (CO₂) and other radiative-forcing trace gases in the atmosphere, such as methane (CH₄), allow short-wave radiation reaching the Earth from the sun to pass through the atmosphere. At the Earth’s surface, this radiation is transformed into heat and largely radiated back to space at long wavelengths. Similar to the glass panels in a greenhouse, however, the gases prevent the long-wavelength heat radiation from escaping to space. The Earth heats up. By emitting large quantities of additional greenhouse gases, humans are amplifying this natural effect. CO₂, the source of which is the burning of natural gas, petroleum and coal, accounts for the biggest proportion of these additional gases. On the other hand, one of the sources of methane is intensive cattle farming; cattle belch methane as part of their digestion process. Methane is also produced as a result of wetland drainage and subsequent processes of decomposition.