The Greenhouse Effect
The ‘greenhouse effect’ is one of many physical, chemical and biological natural processes that shape Earth’s climate. The greenhouse effect plays a major part in creating our warm environment around the Earth’s surface. The atmosphere, consisting primarily of nitrogen (78%) and oxygen (21%), is essentially transparent to incoming (shortwave) solar radiation and to the longwave radiation emitted from the Earth’s surface. Around 30% of the incoming solar radiation is reflected back to space by clouds, aerosols (small particles in the atmosphere) and light coloured regions of the Earth (e.g., covered by snow, ice or desert) and the rest is absorbed by the Earth’s surface and, to a lesser extent, the atmosphere and re-emitted as longwave radiation (see Le Treut et al. 2007 for more detailed explanation; Figure 1). Other constituents of the atmosphere, such as water vapour, carbon dioxide (CO2) and trace gases like methane and nitrous oxide, are largely transparent to the incoming solar radiation but absorb and re-emit longwave radiation.