Comenius

Concentration of greenhouse gases

It is possible to determine the historic concentrations of these gases by various methods of which analysis of tree rings and the isotropic ratio of carbon 13 to carbon 14 in air trapped in ice cores are the most important. These data show that the concentration of carbon dioxide in the earth’s atmosphere is greater now than at any time in the past one million years.

The concentrations of the three principal greenhouse gases in the atmosphere are plotted in Figure 2. The sharp increase since 1800 has been studied and modelled in great depth by the scientists whose work has been collated by the Intergovernmental Panel on Climate Change (IPCC).This increase is above the natural fluctuations in their concentrations and coincides with the start of the industrial revolution in which industry grew very rapidly to produce products that people needed.

Principal sources and sinks

Sources-The largest emissions of carbon dioxide arise through our combustion of fossil fuels to produce useful forms of energy such as heating our homes, moving our transport or generating electricity. Agriculture is the next biggest source via activities such as soil fertilization, farming of animals and growing crops like rice. A further important contribution is from changes in land use including clearing and burning of vegetation and deforestation as 40% of the Earth’s land surface has now been converted for grazing or farming (Figure 3).

Our emissions are increasing because the world’s population is growing as is our individual use of energy. So as we discuss in other SDGs we need to use energy more efficiently and derive our energy from renewable sources which do not result in greenhouse gas emissions.

Figure 3: Sources of carbon dioxide

Sinks-The biggest congregation of greenhouse gases is in the upper atmosphere, which is resulting in global warming. As already noted these gases include not only carbon dioxide, but also methane, nitrous oxides and florinated gases.The oceans are the second most important sink because of their huge volume and the varied life they support from plankton to whales. Forests, particularly tropical forests are also important sinks and the relative importance of the various sinks is illustrated in Figure 4. The ability of the oceans themselves to absorb CO2 will result in them becoming more acidic so decreasing the ability of marine organisms to form calcium carbonate, one of the key substances in building the skeletal of organisms. So like tropical rain-forests, it is important to preserve the biodiversity of the marine ecosystem.