The greenhouse effect is a naturally occurring process where the earth’s atmosphere traps the sun's energy and in turn warms the earth and enables life. The natural greenhouse effect is illustrated in Figure 1 below.
Figure 1 The Natural Greenhouse Effect. Source: NSW Government Department of Environment and Climate Change, 2007.
The natural greenhouse effect is controlled by natural processes that balance the right levels of solar radiation, reflection, absorption and the release of natural greenhouse gases. Greenhouse gases are caused by the breaking down of food, plant and sewerage, clearing of land, use of electricity, burning of fossil fuels (such as coal, oil and gas) and use of industrial processes such as cement and aluminium production.
Over the past 200 years the concentration of greenhouse gases such as carbon dioxide in the global atmosphere has increased. The higher levels of greenhouse gases in the atmosphere has resulted in greater trapping of infrared radiation, this is generally considered to result in the warming of the lower atmosphere. Figures 2 and 3 below illustrate the correlation between carbon dioxide and temperature.
Figure 2: Carbon dioxide and temperature - Last 420,000 years. Source: CSIRO
Figure 3: Carbon dioxide and temperature - Last 1,000 years. Source: CSIRO
The Intergovernmental Panel on Climate Change (IPCC) has concluded there is an increasing body of evidence that human activities are increasing greenhouse gas concentrations and in turn are ‘enhancing’ the natural greenhouse effect, a process commonly referred to as ‘global warming’ the end product of this process is variations in climate and weather being ‘climate change’.