Greenhouse Gases and Their Importance to Life

Greenhouse gases are those in the atmosphere that are essentially opaque to long-wave radiation but virtually transparent to short-wave radiation (Simpson, 1928; Johnson, 1954). They filter out the long-wave component of solar radiation reaching the outer surface of the atmosphere but permit the short-wave radiation to warm the surface of the Earth. Since the re-radiation from that surface is predominantly long-wave, they prevent this energy from escaping. As a result, Arrhenius (1896) proposed that carbon dioxide emitted by combustion in large industrial centres could raise the near-surface atmospheric temperature. In recent years, this warming of the local microenvironment has been found in the heart of many major cities situated away from the Tropics and is called “the urban heat-island effect”. During the last decade, this same process has been claimed to be resulting in “global warming”, i.e., resulting in rising temperatures across the entire earth. This has set off a frenzy of concern, fed in part by overexposure in the media. In many recent research papers, the data has tended to be interpreted as though atmospheric carbon dioxide concentrations were the only possible cause of climatic change. It is true that carbon dioxide is a greenhouse gas, but even the most extreme estimates of the ability of potential manmade carbon dioxide increases in the next century suggest a warming of mean annual air temperature (MAAT) of under 4 C, with most recent models suggesting an increase of less than 2 C. This confirms that the gas is only a minor factor in climatic change (Table 1). In comparison, changes in ocean currents have resulted in a decrease in MAAT over Northern Ellesmere Island of about 30 C in the last 2.5Ma.