We have been hearing a lot about climate change and global warming recently - but do you know what exactly is happening?
The earth is heated by long red rays of heat that enter our atmosphere from the sun. These rays bounce off the earth and are reflected back out into space through the atmosphere. If all the heat escaped back out we would be very cold indeed here on earth. However the carbon dioxide in the atmosphere is able to hold on to enough heat to make life on earth possible. How warm the earth is depends on how much carbon dioxide there is in the atmosphere to hold on to the heat. Two hundred years ago the measurement was 270 parts per million. Carbon dioxide is taken in by plants when they are growing. Their green leaves, in the presence of sunlight, are able to split the carbon dioxide molecule in the air. The plant takes in the carbon part and releases the oxygen part into the atmosphere. All plants are made of carbon - trees, for example, take a lot of carbon out of the atmosphere as they grow and keep it in their trunks and branches.
How does carbon get back into the atmosphere?
When the trees and plants die and rot away, the carbon in their trunks and branches is released back into the atmosphere. It is taken in when they are growing and released when they die and rot away - the Carbon Cycle.
However, not all plants rot away when they die. If the conditions are not suitable for decay, say because of lack of oxygen or because conditions are too acidic, then the dead plants will just stay there. We see this in Ireland today in our bogs. Turf is made from plants that lived two or three thousand years ago but could not rot when they died because conditions were not right. Turf is called a fossil fuel. Similarly coal, oil and natural gas are made from plants that lived millions of years ago - in the Carboniferous Era - but could not rot away because condition were not suitable. All the carbon they took in from the atmosphere when they were growing is still stored as coal, oil or gas in these deposits.
When timber or any of these fossil fuels is burnt, however, the carbon they contain is put back into the atmosphere by the burning process. Since the Industrial Revolution we have been burning vast quantities of coal, oil and gas and the amount of Carbon Dioxide in the atmosphere has increased. There is now 380 parts per million of Carbon Dioxide in the atmosphere - an increase of 40% over the last two hundred years. So more heat is being held by this Carbon Dioxide - known as greenhouse gas - because it acts like the glass in a greenhouse holding in the heat. The world is warming up - what is called Global Warming - and it is causing climate change. The ten hottest years on record on earth have all happened since 1995, with 2005 being the hottest year since records began. Polar ice caps and glaciers are melting at a faster rate because of this increased temperature.
The planet is two thirds ocean and one-third land, so it doesn't heat up evenly. Wind patterns are altered and as a result times of rain and drought are affected. Ocean currents are affected too. In Ireland we are kept warmer than we should be by the Gulf Stream, a warm ocean current that comes to our shores from warmer waters in the South Atlantic. Directly across the Atlantic - Newfoundland, at the samer latitude as us, is kept colder than it should be by the Humbolt Current, which flows down past its coast from the Arctic Ocean. If climate change causes these currents to stop or change direction, Ireland could in fact get much colder.