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Climate Change

Climate is the weather averaged out over a long period of time. This includes temperature, wind speed and direction, precipitation (rain, snow etc) and humidity. During the year, a given location will have weather that follows a particular pattern. Every year will be slightly different, but if you take an average of those weather patterns for many years or decades, you end up with the climate.

What is Climate Change?

Climate change has come to replace term global warming in the media recently. Global warming was a term used to describe the increase in average temperature of the planet during recent decades, due to man's emissions of greenhouse gasses. It is now realised that the effect of greenhouse gasses is not only to increase the global average temperature, but also to change the climate generally including rainfall and severe storms. Climate change is, therefore, a more accurate description of what is going on.

Climate change as a term is most commonly used to describe the man-made effect on the Earth's long term weather patterns, particularly since the 1900's, however it is also used to describe changes made by natural systems such as volcanic eruptions and vegetation.

What is a Greenhouse Gas and what is the Greenhouse Effect?

Greenhouse gasses are those gasses that contribute to the greenhouse effect. The 'greenhouse effect' is a term used to describe how our planet stays warm. The glass in a greenhouse allows light to pass through but prevents the heat from escaping, making the air inside the greenhouse much warmer than the air outside. Greenhouse gasses have the same effect on our planet, letting sunlight in to warm the atmosphere but preventing some of the heat from escaping. The more greenhouse gas that is in the atmosphere, the warmer the earth becomes.

Greenhouse gasses include carbon dioxide, methane, nitrous oxide and water vapour. You may have noticed that clear nights are often a lot colder than nights with cloud cover. This is because the water vapour in the cloud acts like a blanket to prevent the heat escaping. During the day, the reverse happens as the clouds act like giant mirrors, reflecting sunlight back into space before it has had chance to warm the air underneath. Greenhouse gasses other than water vapour do not condense into droplets to form clouds, so they do not become opaque enough to reflect sunlight during the day. This makes them particularly effective at warming the planet.

If there were no greenhouse effect at all, our planet would about 30°C cooler than it is now. We need a certain amount of greenhouse gasses in the atmosphere to keep our planet's temperature 'just right'. Even a change of only 1°C is enough to drastically change the climate and sea levels. Too much greenhouse gas, however, could heat our planet to such an extent that life as we know it would be impossible. A good example of this is the planet Venus. Although it is further away from the sun than Mercury, the temperature on Venus is hundreds of degrees hotter than Mercury due to its own greenhouse effect.

99% of the Earth's atmosphere is made up of a mixture of Nitrogen (78%) and Oxygen (21%). The other 1% is made up of other gasses, including greenhouse gasses. 1% doesn't sound like much, but it is this 1% that determines our climate. Carbon dioxide, Methane, Water Vapour, Nitrous Oxide, Ozone and Halocarbons are the main constituents of this 1%.