Main Greenhouse Gases

Various gases contribute to the greenhouse effect, so that the temperature of the earth exceeds the geological time. A slight change in atmospheric concentration of these gases causes a change in temperature, causing a difference between the glacial period in which Mastodon is walking around the earth and the sultry life of dinosaurs.

The first one is the global warming potential (GWP). This measures the radiation effect of each gas unit over a specified period of time compared to the radiation effect of carbon dioxide (CO2). A certain amount of high GWP gas makes the temperature of the earth higher than that of the same amount of carbon dioxide

The other is the atmospheric lifetime and measures the time it takes to stay in the atmosphere before the gas is removed by a natural process (such as a chemical reaction). Long-life gases may have a greater global warming effect than short-lived gases (assuming GWP are equal).

The table below shows the values ​​of the two main characteristics of greenhouse gases. As new research improves the emission characteristics of each gas and the estimation of atmospheric removal mechanism (HS), the scientific community regularly updates the GWP and atmospheric lifetime values. These values ​​were derived from the fourth IPCC Evaluation Technical Report (AR4) issued in 2007 and were updated in the fifth evaluation report in 2014, but are often used for international reports I will.

The table below shows the relative concentrations of these major greenhouse gases and their sources. Several gases, such as carbon dioxide, are made from natural and man-made processes, but other gases such as fluorinated gases are the result of human industrial activity. Since carbon dioxide is 1,000 times higher than other gases, it is usually measured in parts per million, but it is expressed as one-hundredth of a million to maintain consistency.

* Carbon dioxide is very stable in the Earth 's atmosphere, but each carbon dioxide molecule has hardly changed in different reservoirs such as surface ocean, terrestrial biota and atmosphere. A general estimate of the lifetime of carbon dioxide is 100 years, but this actually only reflects the lifetime of some of the atmospheric carbon dioxide reservoir. The useful life of some parts is up to 1000 years (IPCC 2007, FAQ).

In addition to the main greenhouse gases mentioned above, other greenhouse gases include sulfur hexafluoride, hydrofluorocarbons and perfluorocarbons (see IPCC Greenhouse Gas Inventory). Some greenhouse gases are not usually on the list. For example, nitrogen trifluoride has a high global warming potential (GWP), but only a very small amount. It is impossible to say that a particular gas causes the exact proportion of the greenhouse effect. This is because the total greenhouse effect is not the sum of the effects of each gas because some gases absorb and emit radiation at the same frequency as the other gases. The upper limit of the reference range applies only to each gas and the lower end overlaps with other gases. In addition, some gases such as methane are known to have a large indirect effect which is still quantified.

The three main greenhouse gases produced by human activities are carbon dioxide, methane, and nitrogen. Carbon dioxide is the most common greenhouse gas in humans. It causes over half of the increase in atmospheric greenhouse gases. This is mainly due to the combustion of fossil fuels. Every year, combustion of fossil fuels releases 5 billion tons of carbon dioxide into the atmosphere. (Footnotes) The main source of carbon dioxide is electricity companies (35%), transportation (30%), industry (24%), and 11% from housing (Brisbane Andre College www.ozkidz). The figure below shows a sharp increase in carbon dioxide in the atmosphere