When we use the term 'climate' what we actually mean is the average weather experienced in a region over a long period of time. Meterological variables other than temperature, such as wind and rainfall patterns are constituents of climate. The climate on earth has undergone many changes in the past and this is entirely natural. However, the rate at which the climate has been changing over the past 50 years has led to a consensus amongst scientists that this recent change is likely to be as a result of man's activities. This is what we refer to as 'Climate Change'. Other related terms are the 'greenhouse effect' and 'global warming'.
What is the greenhouse effect?
Certain gases – mainly carbon dioxide (CO2), but also methane (CH4), nitrous oxide (N20), and volatile organic compounds (VOCs) – play an important role in regulating the temperature of the earth’s atmosphere. These are known collectively as the greenhouse gases. Most visible and ultraviolet light coming from the sun is able to reach the Earth’s surface by passing through the atmosphere. Some of this energy is re-radiated back to space in the form of long-wave or infra-red radiation. Natural amounts of greenhouse gases maintain the earth’s temperature at a habitable level by absorbing some of this energy – the ‘greenhouse effect’. However, human activities are increasing the concentrations of greenhouse gases in the atmosphere, leading to a gradual warming of the earth’s atmosphere. It is this enhanced greenhouse effect that is generally referred to as global warming.
Why is climate change occurring?
Human activities, such as deforestation and the burning of fossil fuels, have resulted in an increase in the concentrations of ‘greenhouse gases’ in the atmosphere. The most important of these gases is carbon dioxide (CO2), which has risen from a concentration of 275 parts per million (ppm) prior to 1850 to the current value of 370 ppm. Levels of CO2 are expected to continue rising, and current estimates predict a concentration of 525-950 ppm by the end of this century. The enhancement of the ‘greenhouse effect’ by rising concentrations of these greenhouse gases is largely responsible for the issue of global warming. However, rising temperatures are only one consequence of the enhanced greenhouse effect, with changes to weather patterns and many aspects of the climate such as rainfall and humidity predicted. Collectively, these are referred to as ‘climate change’.
The Intergovernmental Panel on Climate Change (IPCC) concluded in their Third Assessment Report that, " .. most of the warming observed over the last 50 years is likely to have been due to increasing concentrations of greenhouse gases."
What are the predictions for the future climate?
In June 2009 climate change scenarios for the UK were produced by the Tyndall and Hadley Centers on behalf of The Department for Environment Food and Rural Affairs (DEFRA).
The UK Climate projections (UKCP09) provide information on how the Uk's climate is likely to change in the 21st century. Projected changes for the 2020s, 2050s and 2080s are available under the high, medium and low emission scenarios and at 10, 50 and 90% probability levels for different meteorological variables.
