pollution

1. greenhouse effect

2. global warming

2.1. carbon dioxide

2.2. methane

3. low sulphur fuel

4. catalytic converters

5. acid rain

5.1. sulphur dioxide

5.2. nitrogen oxides

5.3. weathering

5.3.1. calcium carbonate

5.3.1.1. calcium oxide

5.3.1.2. carbon dioxide

5.4. dead fish

5.5. trees in Norway

5.5.1. lime (calcium hydroxide)

5.5.1.1. neutralisation

6. burning fossil fuels

6.1. coal

6.2. oil

6.3. natural gas