Greenhouse Gases: Contribution, Features and Trends

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).