How is Our Climate Changing?

Climate can be defined as the average conditions of temperature, rainfall, sunshine and wind experienced by a particular location annually. This is distinct from weather, which describes the mix of the above conditions experienced on a daily basis. Weather may show great variation from day to day but climate gives a generally reliable indication of what we can expect at a particular time of year. For example, April is normally warmer than January (climate) but isolated snowstorms in April are not unknown (weather). Climate change refers to long-term changes in average weather conditions.

It is known that the global climate changes over time in response to influences such as variation in the energy output of the Sun, irregularities in the Earth’s orbit and volcanic activity. As a result the Earth has, in the past, experienced higher temperatures than today and also periods when much of the land surface has been encased in ice. These changes have normally occurred slowly. In recent decades, however, it has been found that global temperatures are rising unusually rapidly.
The warming of the Earth is dependent on the amount of heat stored within the atmosphere. Much of the heat energy reaching us from the Sun is deflected back into space by the atmosphere, reflected from the Earth’s surface or re-radiated from the warmed surface.

The majority of heat energy is retained through absorption by what are known as greenhouse gases in the atmosphere. These include carbon dioxide, methane, nitrous oxide, halocarbons (including CFCs) and water vapour. This process is essential to maintain temperatures at a level suitable for most forms of life. Without the Greenhouse Effect the average temperature of the earth would be only -6ºC. At high concentrations, however, these gases cause temperature increases that have the potential to severely affect the earth’s ecology.

Many natural factors undoubtedly contribute to climate change but there is a growing consensus amongst scientists that the rapid increase in global temperature is related to increasing output of greenhouse gases caused by the industrialisation of human society over the last 200 years, particularly as a result of the burning of fossil fuels, deforestation and the degradation of peatlands.