Greenhouse GasesEarth Journalism Network | 09 June 2016
Greenhouse gases trap heat from the sun within the Earth’s atmosphere through a process known as the greenhouse effect.
Major greenhouse gases include carbon dioxide, water vapor, methane, nitrous oxide, and fluorinated gases. These gases surround the Earth and absorb a lot of the radiated heat from the sun that would have been re-emitted back to outer space without the gases. Without this natural process, planet would on average about 30 degrees Celsius cooler.
Many human activities have artificially raised the concentration of greenhouse gases in the atmosphere. Measurements from Antarctic ice cores show that in pre-industrial times the concentration of carbon dioxide in the atmosphere was about 280 parts per million (ppm) by volume. Since then it has risen rapidly, and reached 387ppm by 2009. According to NOAA, today’s rate of increase is more than 100 times faster than the increase that occurred when the last ice age ended.
Major sources of these emissions are those that involve burning of fossil fuels which releases gases such as dioxide.
Deforestation is another major source, accounting for about one-fifth of all greenhouse-gas emissions from human activities. When forests are cleared or burned this releases carbon dioxide that had been locked away in the living plant material.
Most fertilizers and pesticides used in agriculture are produced using fossil fuels. Large-scale intensive agriculture produces high emissions as it depends heavily on these inputs and well as on fuel for mechanized farming and transportation
Farms are also a major source of a powerful greenhouse gas called methane, which is produced by bacteria that live in waterlogged rice fields and in the digestive tract of large herbivores.
Although these methane emissions are small compared to those of carbon dioxide from other sources, they are still important because methane has a far stronger warming effect. A single molecule of methane traps about 20 times more heat than one of carbon dioxide.
As the average temperature increases, the rate of evaporation increases as well, adding more water vapor to the atmosphere. This generates a positive feedback loop where the increased temperatures increase the greenhouse gas of water vapor which further increases temperatures.
The greenhouse effect is not a new discovery. It was discovered by Joseph Fourier in 1824, experimented on by John Tyndall in 1858, and first reported quantitatively by Svante Arrhenius in 1896.
Since then scientists have provided growing evidence that not only are greenhouse gases increasing in concentration, but also that this threatens dangerous climate change (see Intergovernmental Panel on Climate Change).
Efforts to reduce the atmospheric concentration of greenhouse gases are termed ‘mitigation’.
Experts agree that the fastest, cheapest way to do this is to improve energy efficiency by, for instance, improved insulation and reduced use of electricity.
Other ways to mitigate climate change include actions that remove greenhouse gases from the atmosphere such as by planting trees or using algae to absorb carbon dioxide as they grow.
Other mitigation actions stop such gases from entering the atmosphere in the first place.
Mitigation is a major focus of the UN Framework Convention on Climate Change and its subsidiary treaty, the Kyoto Protocol.
The protocol helps industrialized nations to reduce their emissions with tools such as carbon trading and the Clean Development Mechanism.
Greenhouse-gas emissions vary greatly both within and between countries – but media reports do not always make these variations clear.
While China now emits more than any other nation, its emissions per person are still much lower than those in most other countries. For a comparison, Wikipedia has tables that rank countries according to their total (here) and per capita (here) emissions.
The Carbon Disclosure Project is a good source of information on what companies are doing to measure, report and reduce their emissions. It has information from over 2000 companies in 60 countries.
To find out what countries are doing to reduce emissions, journalists can check their national communications to the UN Framework Convention on Climate Change, which also has a register of greenhouse gases produced by industrialized nations.
Journalists who report on local weather conditions such as temperatures should also check what is happening around the world. For instance, January 2010 was extremely cold in the United Kingdom and eastern United States, which led some people to think the greenhouse effect was not real. But globally, January 2010 was the hottest on record.
It is also important to remember that the El Niño / La Niña cycle of warmth and cooling in the Pacific Ocean affects temperatures worldwide too.
On the subject of mitigation, it is important to investigate new methods as greenhouse gases are a worldwide issue.
FURTHER READING AND RESOURCES
IPCC 4th Assessment Report – Synthesis report