What Causes Global Warming?
`Carbon dioxide is the single most important factor in global warming’.
(D.Waugh, 1994, The Wider World, Nelson and Sons Ltd.)
Carbon dioxide accounts for 63% of the greenhouse gases in the atmosphere and levels of CO2 in the atmosphere are currently at their highest for 160,000 years.
Carbon dioxide enters the atmosphere quite naturally, when we breathe, when plants decay or when volcanoes erupt.
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But since the end of the 18th century, the amount of carbon dioxide in Earth’s atmosphere has increased from about 280 parts of carbon dioxide per million parts of air, to about 370 parts per million. Scientists believe this is because around a quarter of the CO2 in the atmosphere has been added by human actions, while the rest comes from the natural world.
Power plants, factories and cars all give off large amounts of carbon dioxide as they burn fossil fuel. According to reports, by 2010, there may be over 800 million motor vehicles in the world and most of them will produce gases, which add to global warming. In fact most of the world’s energy is generated using coal, gas and oil. Non-renewable fossil fuels and information on their use can be found in the Energy and Resources factfile.
Until recently, carbon dioxide levels remained balanced by sinks – areas such as forests, which absorb carbon dioxide. Trees are nearly 50% carbon. During the growth processes, trees remove or sequester carbon dioxide from the atmosphere, convert it to carbon-based tissues during photosynthesis, release oxygen as a by-product and the carbon then remains tied up in the tree tissue until they die or are harvested.
Deforestation in Brazil
One of our growing problems is that because many forests are being cut down to meet human needs (farming, logging etc), we are leaving fewer sinks to absorb the carbon dioxide in the air. Another problem is the clearing process itself. As forests are made largely from carbon, if they are burned when they are cleared, burning releases the carbon that was stored in the trees as carbon dioxide. Clearing forests by burning trees has released 1.6 billion tonnes of carbon dioxide into the air.
Currently, around 200,000 acres of rainforest are destroyed every day and scientists are uncertain exactly how this will affect our climate. But what could be the potential consequences of global warming?