Our planet has been gradually heating up since the last Ice Age ended 10,000 years ago. Temperatures have steadily increased at around a quarter of a degree for every 1,000 years. Until recently. During the last 100 years temperatures have increased by twice that amount. As if that wasn't alarming enough, all the warmest days occurred during the last decade. Experts are now predicting that temperatures are set to increase by as much as 6 degrees centigrade during the coming century - a rise that could herald devastating consequences. So, what's going on and what are we doing to prevent disaster?
 

 
Greenhouse Effect
The terms 'global warming' and 'greenhouse effect' only hit the headlines in the 1980's. Environmental scientists working in Hawaii found that carbon dioxide in the atmosphere had increased by 8 percent between 1959 and 1983. They attributed these figures to man's accelerating usage of fossil fuels. Scientists determined that harmful gasses from cars, industry, and farming were actually the root of our planet's woes.
 
However, both global warming and the greenhouse effect are essential to life on Earth. As the sun warms the earth, certain gasses in the atmosphere act like the glass of a greenhouse - trapping heat and keeping the planet warm enough to support life. Without them we'd be plunged down to a freezing -18 degrees centigrade. The problem only occurs when subtle changes upset the balance.
 
Scientists determined that increased concentrations of water vapour, CFCs, methane, and carbon dioxide were actually harming our environment. Collectively known as 'greenhouse gasses', intensified amounts of these gasses effectively insulate the Earth and prevent heat from escaping. This is causing global temperatures to rise to alarming levels.
 
Ozone Layer
Some greenhouse gasses, like carbon dioxide, appear naturally in the atmosphere. But CFCs (short for chlorofluorocarbons) are a direct result of industrial processing and chemical engineering.
 
CFCs are found in aerosols, refrigerator coolants and air conditioners. They are much more harmful than other greenhouse gasses. CFCs are believed to be responsible for destroying a part of the atmosphere known as the ozone layer. At an altitude of around 10km, the ozone is a protective layer that reduces the amount of ultraviolet light emitted by the sun reaching the Earth. Besides being harmful to our skin, increased UV light also contributes greatly to global warming.
 
Despite the threat of CFCs, carbon dioxide still causes the most damage to our environment. That's because there's so much more of it being produced. In fact, carbon levels in the Earth's atmosphere have risen by over 30 percent since man began relying on fossil fuels during the industrial revolution 160 years ago. Motor vehicles are now responsible for around 15 percent or 400 million tonnes of our total carbon output. Scientists know that if car numbers increase at the present rate there will be more than a billion on the road in 2025.


Atmospheric Pressure
 
Of course, all animals breathe oxygen and exhale CO2. Plants and microorganisms like plankton in the ocean do exactly the opposite - they convert CO2 into oxygen through photosynthesis. It's estimated that photosynthesis converts around 60 billion tons of carbon dioxide every year - in fact, it's the most effect way to reduce carbon levels. However, this is almost perfectly balanced with the amount of animals exhaling CO2. This is why the destruction of the Earth’s rainforests is so critical in upsetting the Earth’s ecosystem. More than 50 percent of the forests that existed after the last Ice Age have disappeared. Rainforests in South America, Asia, and Africa are being cut down 10 times faster than First World nations are re-planting them. It doesn't take a genius to figure out that this current situation is unsustainable.
source: Discovery Channel. (http://www.discoverychannel.co.uk) Photo: Corbis