Global warming is simply defined as the steady increase in the Earth's surface temperature. It is considered to be primarily the result of a phenomenon known as the 'greenhouse effect'. The Earth's atmosphere is composed of gases, as shown in Table 1. Some of these gases have fixed proportions, such as nitrogen and oxygen, whilst it is the greenhouse gases that vary in proportion. The 'greenhouse effect' is where solar radiation becomes trapped in the Earth's atmosphere making the atmosphere warmer. On the whole, the amount of solar radiation absorbed by the Earth and the amount reflected back into space balance each other out, keeping the Earth's surface temperature constant. Naturally occurring greenhouse gases in the atmosphere such as carbon dioxide, methane and water vapour absorb long wave terrestrial radiation (reflected, short wave solar radiation), thus acting to keep the Earth warm at an average surface temperature of 15oC. It is only when concentrations of such gases increase that more radiation can be absorbed. This increased capability of the Earth's atmosphere to absorb more radiation has led to a term known as the, 'enhanced greenhouse effect'. This means that the Earth retains more heat than is being radiated back into space, resulting in global warming. It is known that in the Earth's history, the average temperature of the Earth has fluctuated constantly, resulting in periods of ice ages and warmer interglacial periods. It appears that the most recent ice age reached its maximum approximately 20,000 years ago, and that the Earth is now in a warmer interglacial period. However in the past century or so, it has been apparent that the Earth is experiencing an unprecedented rate of warming (Graph 1), and evidence collected suggests that human society may be to blame. Approximately 200 years ago, Great Britain became the first country to industrialise. The primary cause for such rapid growth in industry was the utilisation of fossil fuels. Fossil fuels include coal, natural gas and oil, and it was the burning of these, especially coal that literally powered the Industrial Revolution. Since then, much of the world has industrialised, burning even more fossil fuels. Nowadays, fossil fuels supply over 80% of the World's energy needs. However, the burning of such fossil fuels is having serious consequences. When a fossil fuel is burned it releases greenhouse gases. The most important of these gases is carbon dioxide. Carbon dioxide is a greenhouse gas that strongly absorbs infrared radiation. On average it comprises only 0.0003% or 365ppmv (parts per million of volume) of the atmosphere, therefore it can be seen that not much carbon dioxide released into the atmosphere is required for this value to change significantly. Levels of carbon dioxide have steadily risen in the atmosphere in recent times (Graph 2), levels that have not be seen on this planet for millions of years and this has had the consequence of warming the atmosphere, in particular the lower atmosphere. A further consequence of this is that as the air near the surface warms, more water will evaporate into the air from the oceans increasing the water vapour content of the air. The excess water vapour, which itself is the most abundant greenhouse gas, will hence increase the greenhouse effect and accelerate global warming even further. This is known as the water vapour greenhouse effect feedback. Methane is another greenhouse gas. It currently has a concentration of 1.745 ppmv3, considerably less than carbon dioxide, but is rising at a rate of 0.6% per year. For the last two thousand years up till 1800 however, this value was only 0.7 ppmv4. It is a damaging greenhouse gas that is increasingly becoming more of a concern because the enhanced greenhouse effect caused by methane is about 7-8 times that of carbon dioxide4. Methane can form naturally, such as in marshlands, but the man-made sources include oil wells, coal mining and agricultural activities. Agricultural activities are the main source of methane and are from sources such as rice paddy fields, enteric fermentation from cattle and other livestock. Rice forms the staple diet for almost 50% of the world's population and because the world's population is increasing exponentially the production of rice in paddy fields is increasing rapidly too. This can therefore only mean that concentrations of methane will continue to increase, exacerbating the greenhouse effect. One other, yet minor greenhouse gas is nitrous oxide (laughing gas). It forms naturally, but can also be man-made as well. Sources include fossil fuel combustion, nitrogenous fertilisers and animal waste. On average it has a concentration of about 0.3 ppmv in the atmosphere. When compared to carbon dioxide, this amount is minimal, but nitrous oxide is thought to be responsible for at least 6% of the greenhouse effect so far2, with levels of this gas rising about 0.25% per year1. It is considered to be of great concern because the lifetime of nitrous oxide is about 120 years1, which means that this gas will remain effective for many years to come. Another greenhouse gas is Chlorofluorocarbons (CFCs). They are man made chemicals that because of its special properties was widely used in items such as refrigerators aerosol spray cans. Although there has been a complete ban on using CFCs, the effect of this gas when it was in use on the atmosphere was enormous. The average concentration of CFCs is currently about 1ppbv (parts per billion by volume)1, this is incredibly small, even compared to nitrous oxide, but a single CFC molecule is 10,000 times more effective at absorbing heat than a carbon dioxide molecule and is why CFCs are a significant enhancer or the greenhouse effect. CFCs also have a long lifetime and destroy ozone, a gas found in the stratosphere. Although this gas exists in very small concentrations, 0.02-0.07 ppmv, it protects the Earth from harmful radiation from the Sun. Deforestation also plays a role in enhancing the greenhouse effect. It's responsible for roughly 25% of all carbon dioxide emissions entering the atmosphere, by the burning and clearing of approximately 34 million acres of trees per year. Trees are capable of storing vast amounts of carbon dioxide, an acre alone of forest can store up to 2.8 tonnes of carbon dioxide. When forests are cleared, more carbon dioxide enters the atmosphere as less is absorbed, thus enhancing the greenhouse effect. Over the past century, there is evidence to suggest that global warming is happening. It has been calculated using historic records that the average surface temperature of the Earth has raised by 0.6 oC in the last 100 years. This is clearly seen in graph 1. Although this increase seems negligible, it is a significant rise for such a small time. It has also been recorded that 8 of the 10 warmest years since 1860 have occurred during the last decade. This occurrence is remarkable and indicates that the Earth is warming at an alarming rate. Warming of the atmosphere has equally resulted in the warming of the oceans. As the oceans warm up, they expand, causing sea levels to gradually rise. In the last 100 years, the global sea level has risen by about 10 to 25 cm (Graph 3). The problem is intensified by melting ice caps at both the Arctic and Antarctic. To date, Arctic sea ice has shrunk by about 250 million acres. Ice melting on such a large scale adds vast amounts of water into the oceans, accelerating sea level rise that threaten many low lying coasts across the world from serious flooding. More frequent, extreme weather events are another indicator that global warming is taking place. The warming of the atmosphere and the oceans has in some regions of the world has enhanced the hydrological cycle. This has produced more intense storms and hurricanes, extensive flooding and in some parts of the world, severe drought. It appears that extreme events that normally occur rarely are becoming more common. It has also been recorded that the majority of all the world's glaciers are retreating. The rise in lower atmospheric temperature is melting the ice of the glaciers causing them to shrink. The Grinnell Glacier, USA, has already retreated by 90%. This is similar across the world. Further evidence of global warming can also be found in ice cores. Analysis of ice cores taken from the Dunde Ice Cap in the Qilian Mountains, northwest China indicate that the years since 1938 have been the warmest in the last 12,000 years. The ocean's coral ecosystems are also being harmed. Coral is being bleached by rising ocean temperatures as the water is simply too warm for the coral to survive. Higher temperatures are also reducing the calcium content of the water, limiting coral growth. It has been estimated that 25% of the world's coral reefs have already been destroyed by global warming and pollution3. During the past century, concentrations of greenhouse gases such as carbon dioxide, methane and water vapour have risen sharply in the atmosphere enhancing the greenhouse effect. As a result of greater concentrations of these gases in the atmosphere, more radiation from the sun becomes trapped thus acting to warm the earth. The last 100 years has experienced a rate of warming never witnessed before and this global warming is proving to have consequences for both the environment and human society. Sea levels are rising, the world's weather is changing and with the world's population rapidly increasing, this problem is set to continue. 