In what ways have human activities contributed to global warming?

With this question it is important to focus on the human contribution to global warming rather than explaining why global warming is happening. 

Start your answer by explaining that carbon dioxide and methane are 'greenhouse gases'. This means that they absorb heat. Therefore more carbon dioxide or methane in the atmosphere means more heat will be absorbed and the earth will get warmer.

Humans have caused an increase in carbon dioxide in several different ways:

- Deforestation (the cutting down of trees) means less carbon dioxide is being absorbed by trees to be used in photosynthesis. 

- The burning of trees and fossil fuels such as coal releases extra carbon dioxide as they are stores (otherwise known as carbon dioxide 'sinks').

Human activities that cause an increase in methane include:

- Cattle farming

- The growing of rice in rice fields 

- Landfills; as the waste in landfills breaks down it releases mostly methane and carbon dioxide.