What are greenhouse gases?

Most of the earth's atmosphere is made up of Nitrogen (78%) and Oxygen (21%). But various trace gases are also present, in very small quantities, and some of these gases regulate our climate. CO2 accounts for the largest proportion of these trace gases and is the most important greenhouse gas. It has been in the atmosphere for over 4 billion of the earth's 4.6 billion year geological history - in larger proportions (up to 80%) than today.

• Over millions of years, CO2 was gradually removed from the earth's atmosphere, as the early organisms evolved photosynthesis and locked away the CO2 as carbonate materials - eventually resulting in the creation of oil, coal and petroleum.
• CO2 is still being removed from the atmosphere by photosynthesising plants and by dissolving in water, especially on the surface of oceans
• At the same time, some CO2 is continually being released into the atmosphere from natural sources, such as plant decay, volcanic eruptions and the waste products of animal respiration. When it enters the atmosphere, it stays there for about 100 years.
• Burning fossil fuels releases CO2 that was stored millions of years ago, increasing the concentration of greenhouse gases in the atmosphere.
• Deforestation also releases the carbon that is stored in the trees and the reduced tree cover results in less CO2 being removed from the atmosphere.

Concentrations of CO2 in the atmosphere are higher in the northern hemisphere, where more fossil fuels are being burned. Since the industrial revolution began, atmospheric levels of CO2 globally have increased by 30%. It has been predicted that by 2100, CO2 concentrations in the atmosphere could rise to double the level that existed before the industrial revolution, while others predict that these changes could happen as early as 2045.

What are the impacts?

Global warming could result in changes to weather patterns; with more extremes of weather conditions, increased rainfall and sea level rises - with increased risk of flooding in many areas. These climate changes could affect us in many ways - our health, agriculture and wildlife. The types of crops that we are able to grow in the UK and other countries could alter (the UN has predicted a shift northwards of 200-300km for every degree of warming). There could be an increase in agricultural pests and changing climate and habitats will alter the range of plants, animals, birds and fish that can live here. Some plants or wildlife that are unable to adapt or migrate will die out. Milder winters may enable the spread of disease as bacteria and other pathogens are able to survive the winter and spread to areas that were previously too cold for them to survive. There could be increases in the number of hot weather related deaths; food poisoning cases and a higher incidence of diseases that are affected by UV light, such as cataracts and skin cancer.

What is being done about climate change?

The UK has committed to reducing CO2 emissions by 20%, by 2010, and seeks a 60% reduction in emissions by 2050. Various initiatives have been set up by the Government to help meet these commitments. For example:

• The Energy Efficiency Commitment requires electricity and gas suppliers to achieve targets for the promotion of improvements in domestic energy efficiency. This is usually delivered in the form of grants and advice.
• The Climate Change Levy places a tax on the use of energy in industry, commerce and the public sector, with offsetting cuts in employer's National Insurance contributions and additional support for energy efficiency schemes and renewable sources of energy. This will encourage users to improve energy efficiency and reduce emissions of greenhouse gases.
• The Renewables Obligation requires all electricity suppliers to produce 10% of the energy that they sell from renewable sources by 2010.
• The Low Carbon Buildings Programme provides grants towards installing micro-generation technologies.

These and other initiatives are designed to help households, businesses and the public sector to make changes and reduce CO2 emissions. But in order to make a difference, everyone needs to take action.

What can you do?

Almost half of the UK's CO2 emissions come from the little things that we do every day, like leaving lights on, overfilling the kettle and leaving appliances on standby. By making relatively small changes in our daily lives, we can make a significant contribution to limiting climate change. We can all make a difference.

Information on what you can do to reduce CO2 emissions and combat climate change, can be found on our Energy Efficiency and Renewable Energy pages, or visit the Energy Saving Trust website