After reading this article you will learn about:- 1. Contribution of Greenhouse Gases 2. Features of Greenhouse Gases 3. Global Trends.
Contribution of Greenhouse Gases to Global Warming:
The gases in the atmosphere that act like glass in a greenhouse are called greenhouse gases.
These are as follows:
1. Carbon dioxide (causes 9—26%)
2. Water vapour (causes about 36 – 70%) of the greenhouse effect (not including clouds)
3. Methane (causes 4 – 9%)
4. Ozone (causes 3 – 7%)
5. Chlorofluorocarbons (CFCs)
6. Oxides of Nitrogen.
The contribution of various activities on greenhouse gas emission is given in Fig. 14.2. Subsequently the chronological rise and other features of greenhouse gases are given in Table 14.1.
Features of Greenhouse Gases:
What determines the contribution of a greenhouse gas to global warming?
1. Concentrations of H2O and CO2 are the two biggest contributors to the atmospheric warming because of their higher concentrations.
2. Lifetime of each greenhouse gas.
3. The longer-lived a gas is, the higher the contribution, e.g., N2O contribution > CH4.
4. Effectiveness as an infrared absorber CFC- 11 and CFC-12.
Among the greenhouse gas, the contribution of CO2 is very significant. The concentration atmospheric CO2 level over a century has increased in alarming level as recorded from various observatories (Fig. 14.3) and it is intimately connected with rising temperature (Fig. 14.4).
Global Trends of Greenhouse Gases:
However, there are balance in CO2 level to some extend due to a number of activities (Fig. 14.5).