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The Kyoto Protocol | Carbon Dioxide | Methane | Global Warming On Other Planets | Other Greenhouse Gases | UK Greenhouse Emissions
The Kyoto Protocol is a legal agreement, monitored by the United Nations, in which the signatory nations have agreed to reduce 'dangerous anthropogenic [man-made] interference with the climate system'. That is, to reduce emissions of greenhouse gases. After a great deal of heated debate, the participating countries have signed up to reduce six key greenhouse gases (carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons, and sulphur hexafluoride). The reduction targets must be achieved between 2008 and 2012 and, in theory, a country can be prosecuted if it fails to do so.
The target reductions vary from nation to nation. The developed countries have clubbed together to achieve a combined minimum reduction of 5% in their collective emissions. To do this, Switzerland, most Central European and Eastern European states and the European Union must reduce greenhouse gasses by 8%. The EU will meet its 8% group target by distributing different rates among its member states – the UK's target is 12.5%. The US was to reduce its emissions by 7%, but has since pulled out of the agreement. Canada, Hungary, Japan and Poland are to reduce by 6%. Russia, New Zealand and Ukraine must stabilise their emissions. While Norway may actually increase their emissions by up to 1%, Australia up to 8%, and Iceland 10%, if they so wished.
In reality, the cuts will have to be much larger as many nations have actually increased emissions since 1990, so a greater reduction will be needed to return levels to pre-1990 amounts, as the protocol requires.
Carbon, a major constituent of many molecules, minerals and gases, is one of the most important elements on Earth. It's constantly being naturally cycled between the oceans, atmosphere and biosphere, in a continuous transportation mechanism known as the carbon cycle. The most important way that carbon cycles between these natural reservoirs is in the form of carbon dioxide gas (CO2).
Carbon dioxide is a greenhouse gas. As with other greenhouse gases, it is mostly transparent to incoming short-wave heat energy from the Sun. However, it effectively traps the long-wave heat energy that is re-radiated from Earth. This longer wavelength heat energy is absorbed by carbon dioxide, some of which is in turn re-emitted back towards Earth's surface. So in effect, the billions of carbon dioxide gas molecules in the atmosphere act a thermal blanket, increasing the temperature of the atmosphere below. The more carbon dioxide molecules in the atmosphere, the more effective the thermal blanket.
Water vapour is the most powerful greenhouse gas, but the amount contained in the atmosphere is not substantially affected by human activity. This isn't true for carbon dioxide and it's for this very reason it is such an important greenhouse gas. By analysing the amount of carbon dioxide trapped in ice, it's known that pre-1750 (before the industrial age) carbon dioxide levels in the atmosphere were stable at 280ppm (parts per million). Today the level has dramatically risen to 379ppm, an increase of 34%, and its highest level for half a million years.
Methane (CH4), a molecule of carbon and hydrogen, is the main component of natural gas. It's often known as marsh gas since it's commonly seen bubbling up from marshlands, the product of slowly decaying organic materials. There are known to be huge reservoirs of natural methane stored under the surface of the oceans. Ruminating cattle, rice cultivation and the burning of biomass and fossil fuels generate the majority of man-made methane currently in the atmosphere.
While the amount of methane in the atmosphere is far less than that of carbon dioxide, its potential to trap long-wave heat energy radiated from Earth is much greater. The greenhouse effect caused by a molecule of methane is around 7.5 times greater than that caused by a molecule of carbon dioxide. And although methane's lifespan in the atmosphere is much shorter than carbon dioxide (around 12 years in comparison to up to 200 years), its concentration has more than doubled since pre-industrial times, shown by concentrations extracted from ice cores.
In total, the amount of methane generated by human activities outweighs that generated by natural sources, and its abundance in the atmosphere can be seen to closely follow the growth in world population since the Industrial Revolution. This trend is alarming since the world population is expected to double during the 21st century. So unless strict measures are employed to curb its release into the atmosphere, the contribution to global warming from methane is likely to double.
Global warming isn't just restricted to Earth. Both our neighbouring planets, Venus and Mars, are warmed by the effects of greenhouse gases in their atmospheres. In fact, from comparing these three rocky worlds, scientists have gained an invaluable insight into how the quantity of greenhouse gases in a planet's atmosphere can radically affect the climate and surface conditions – conditions which are crucial for life.
On Earth, the majority of carbon lies not in the atmosphere, but in the oceans and rocks. Just 0.00035% of Earth's atmosphere is made of carbon dioxide. However, this carbon dioxide, along with water vapour and other small amounts of greenhouse gasses, is enough to raise the average surface temperature of Earth by around 30°C. Without it, Earth would be frozen.
By comparison, the atmosphere of Venus is composed of 96% carbon dioxide (260,000 times more than Earth) and is much denser, containing around 100 times more gas than Earth's. The thick dense carbon dioxide atmosphere on Venus has led to a 'run away' greenhouse effect, with surface temperatures soaring to around 460°C, hot enough to melt lead, and three times greater than otherwise expected.
Mars too has an atmosphere made mainly of carbon dioxide (95%), but there the atmosphere is over 100 times thinner than Earth's. So even though, like Venus, the Martian atmosphere is almost solely made of carbon dioxide, it's actually so thin that the effect of greenhouse warming lifts the global temperature by just 6°C.
While carbon dioxide and methane are the best known greenhouse gases, they are not alone in contributing to global warming. Nitrous oxide and the halocarbon gases are also powerful traps of long-wave heat energy emitted by Earth.
Nitrous oxide (N20), better known as laughing gas, plays an important role in the chemistry of life. Although scarce in the atmosphere, with a mean concentration of just 311 parts per billion (a thousand times less abundant that carbon dioxide), a molecule of nitrous oxide is some 200 to 300 times more effective as a greenhouse gas than a molecule of carbon dioxide. Furthermore, it is longer lived, typically lasting some 150 years in the air. These two facts make nitrous oxide a dangerous greenhouse gas, one that has increased by approximately 9% in the atmosphere since the Industrial Revolution.
The halocarbons are man-made compounds of carbon which combine with one or more of the five elements called halogens: fluorine, chlorine, bromine iodine and astatine. The most common are the CFCs (chlorofluorocarbons) and the HCFCs (hydrochloroflurocarbons). CFCs are particularly effective greenhouse gases, being between 3000 and 13,000 times more powerful at global warming than carbon dioxide. The abundance of CFCs in the atmosphere before the 1950s was practically zero. However, during the 1960s and 1970s, they escaped into the atmosphere from millions of scrapped refrigerators, where the gas was used as a coolant. CFC production was controlled in the 1980s and 1990s, owing to their destructive effect on the ozone layer, which protects us from harmful ultraviolet radiation. And so their contribution to global warming is expected to decline rapidly over the coming decades.
The UK's contribution to greenhouse gases is not a new phenomenon. Since the time of William Shakespeare, carbon dioxide has been added to the atmosphere from burning solid fuels such as wood, coal and peat. But the real increase came during the 1900s. UK carbon dioxide emissions peaked in about 1960, with the bulk coming from burning coal and oil. In 1960, the UK contributed approximately 180 million tonnes of carbon dioxide from coal burning and 90 million tonnes from burning oil. Since then there has been a gradual decline in the amount of carbon dioxide released from coal burning, with a notable trough in 1984 owing to the miners' strike. The contribution from oil burning on the other hand has increased and stood at approximately 110 million tonnes in 1999.
Natural gas emissions rose from nothing in the 1950s to around 57 million tonnes by 2000. The reason is simple. Here in the UK, less coal is burnt, and indeed mined, than at the beginning of the 20th century, while natural gas from the North Sea has become far more important as a fuel for heating our homes.
Looking towards the future, a revised version of the National Allocated Plan (the amount of carbon dioxide which Britain is allowed to produce as a signatory of the Kyoto Protocol) is set at 756 million tonnes of carbon dioxide a year. However, many consider this too large if the industrial nations are to act on reducing global warming.
1. Introduction | 2. Rising Temperatures | 3. Predicting Global Warming | 4. Complicating Factors | 5. Predicting 2080 | 6. Spring 2080 | 7. Summer 2080 | 8. Autumn 2080 | 9. Winter 2080 |10. Quick Guides | 11. Find out more | 12. Credits