Friday, January 20, 2012

CLIMATE CHANGE: Greenhouse effect

The emission of greenhouse gases - such as carbon dioxide and methane - as by-products of industry and agriculture is having a global impact on temperature and weather systems.

Consequences of resource exploitation
When fossil fuels are burned - by industry, in power stations and by vehicles and planes - gases (as unwanted by-products known as carbon emissions) enter theatmosphere. Carbon dioxide (CO2), in particular, is given off when fossil fuels, such as oil and coal, are burned. Although these gases have always been present in the world's atmosphere, their concentration is gradually increasing as more and more fossil fuels are burned.

The inequality in the use of resources between MEDCs and LEDCs is shown by measuring and comparing their carbon emissions per capita. Countries that use a lot of fossil fuels to produce energy to power industry, produce electricity and heat homes, also produce a lot of carbon gasses.

Greenhouse gases
Scientists believe that the build-up of so-called greenhouse gases in the atmosphere acts like a blanket or greenhouse around the planet; heat is trapped inside the Earth's atmosphere. This is the greenhouse effect, and the resulting increase in global temperatures is called global warming.
  • Plants and trees need CO2 and use it up. However, if there is too much CO2in the atmosphere - due to factories and power stations, combined with a reduction in the number of trees, through deforestation - CO2 builds up in the atmosphere.
  • This build-up of CO2 is believed to contribute to global warming through the greenhouse effect. This is why CO2 is called a greenhouse gas.
  • The biggest producers of CO2 in the world are the United States (USA), China, Russia, Japan, India, Germany, United Kingdom, Canada, Italy and Mexico.
  • The largest producers by far are the USA and China.
The diagram below shows the countries that contribute the biggest percentage of the world's carbon emissions.

Countries contributing to carbon emissions

How the greenhouse effect works
It's thought that the build-up of greenhouse gases impacts on global temperature in two ways:
  1. The gases allow more of the sun's rays to enter the atmosphere. Some solar radiation is still reflected back into space by the outer parts of the atmosphere, but it's believed the amount reflected back is gradually reducing.
  2. At the same time, the greenhouse gases absorb more of the solar radiation that is reflected back from the Earth's surface - trapping heat and keeping it in the atmosphere. The ability of the atmosphere to capture the Sun's warmth is essential for life on earth. But if significantly more warmth is being captured, this is bad news for the planet.
The greenhouse effect

Another group of greenhouse gases includes the chlorofluorocarbons (CFCs). CFCs have been responsible for depleting the ozone layer as they attack and destroy ozone molecules.
  • The ozone layer is a high level layer of gas in the stratosphere. The ozone helps to keep out harmful ultraviolet rays that cause sunburn to human skin and damage to plants.
  • The resulting ozone holes let harmful ultraviolet radiation in and add to the greenhouse effect.
  • CFCs can be used in aerosols, such as hairspray cans, fridges and in making foam plastics.
  • CFCs were banned in many countries in the mid-1990s after it was found that they were breaking up the Earth's ozone.
  • Scientists say the hole in the ozone layer over Antarctica could disappear within 50 years.

Implications of global warming
Scientists, politicians and industrialists continue to debate the causes of global warming, with some arguing that it is a natural process that's been going on for centuries. However, the Intergovernmental Panel on Climate Change (IPCC)- established by the United Nations in 1988 - has stated the evidence suggests that human activity does affect global warming, in particular through the release of greenhouses gases and the use of aerosols.

There is also debate over how quickly the earth is warming up. Some scientists estimate that atmospheric temperatures could rise by 1.4°C - 5.8°C in the next 100 years. Others believe that they will rise more slowly.

Global carbon emissions

Whatever the causes and timescale, the implications of global warming are very serious.
  • The map above shows which countries are responsible for the most emissions. LEDCs want to develop and to catch up with MEDCs and this normally means using more energy and burning more fuel. So global warming could threaten development.
  • Global warming could melt the world's ice caps and glaciers, leading to an increase in sea levels. Some scientists estimate that over the next hundred years sea levels could rise by between 10 cm and 90 cm - making many coastal areas around the world uninhabitable.
  • Global warming could also affect the weather patterns, leading to more droughts, flooding and extreme weather, such as hurricanes.

Courtesy: BBC

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