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Human activity is predicted to increase the earth's average air temperature by 2°C over the next century.
Carbon dioxide, methane and nitrous oxide account for most (approximately 90%) of the manmade global warming.
 
Even assuming 100% emissions, HFCs will never contribute more than 1-2% of man made global warming by 2030. 
 
What is Global Warming? 
 
Records show that the earth's average surface air temperature has increased by between 0.3-0.6°C over the last century. Scientists of the Intergovernmental Panel on Climate Change (IPCC) now agree that human activities are having a noticeable impact on global climate and anticipate a further increase of 2°C by the 2100.
 
A number of factors affect global climate, such as the earth's orbit around the sun and volcanic and solar activity. The greenhouse effect is a natural phenomenon, without which the earth's surface temperature would be no more than -15°C and life could not be sustained. It works via certain gases in the atmosphere which create a barrier to the infrared radiation of the sun's rays reflecting from the surface of the earth, the most important one being water vapour (or clouds).
 
It is the addition of manmade global warming gases to the atmosphere that is believed to be causing an increase in average atmospheric temperatures. A decision to reverse this effect was taken at the United Nations Framework Convention on Climate Change (UNFCCC) in Rio de Janeiro in 1992, when international action was agreed to identify and control the release of man-made greenhouse gases. 
 
What Makes a Gas a Greenhouse Gas? 
 
It is the ability of the gas to absorb radiation that gives it its greenhouse properties. The strength of the effect of a particular greenhouse gas depends on three factors;
 - The quantity of gas emitted in the atmosphere; 
 - Its atmospheric lifetime; and
 - The infrared reflecting properties of the molecule.


The most abundant manmade greenhouse gas is carbon dioxide. Others include water vapour, methane, nitrous oxide, fluorocarbons and tropospheric ozone. Some manmade pollutants, primarily nitrous oxide and volatile organic compounds (such as hydrocarbons) have an indirect greenhouse effect as they react and generate ozone in the lower atmosphere, causing smog.

Focus on Carbon Dioxide

Atmospheric concentrations of carbon dioxide are 30% higher than levels of 200 years ago. Human activities results in over 26 billion tonnes of carbon dioxide being released each year and this number is growing by 1-3% p.a.. Burning fossil fuels (coal, oil and gas for example) to generate energy produces 80% of these emissions, while land-use changes, such as deforestation, contribute the remaining 20% of carbon dioxide emissions. The problem is compounded as carbon dioxide has a long atmospheric lifetime. Around 25% of carbon dioxide emitted this year will still be in the atmosphere contributing to global warming in 500 years time.

The long lifetime of the gas and the enormous quantities in which it is emitted mean that carbon dioxide is responsible for more than 60% of the total manmade greenhouse gas contribution. 
 
Other Gases 
 
The two other gases making the most direct contribution to global warming are
methane at just under 21% and nitrous oxide at just under 7.5%. 
 
METHANE: Has a global warming potential 11 times higher than carbon dioxide. But with an atmospheric life of only 11 years and annual emissions of a little over 500 million tonnes, its contribution to global warming is much less than that of carbon dioxide. Around 70% of emissions come from activities such as agriculture, waste disposal and mining. 
 
NITROUS OXIDE: Has a global warming potential 310 times greater than carbon dioxide. Its atmospheric life expectancy is 120 years and annual emissions are 13 million tonnes. Nearly 40% of emissions come from industrial activities, such as agrochemical use and nylon manufacture.
 
The UNFCCC includes HFCs in the basket of "other gases" that contribute to global warming. However, the consideration of the relatively high GWPs of fluorocarbons must be set against the relatively small volumes emitted, the energy efficient quality of their applications and their role in replacing CFCs (which themselves have a much greater global warming impact than HFCs).
 
Even as emission volumes increase up to 2030 - due to demand to replace CFCs - HFCs are projected to have a direct impact on global warming of approximately 1-2% (a percentage that takes into account GWP, atmospheric life expectancy and projected emissions).
 
IGiven the relatively small contribution of HFCs to overall global warming, they receive little attention in the Kyoto Protocol process.

This has led to international efforts to manage HFCs under the Montreal Protocol, but account for them under the UNFCCC framework.
 

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