The atmosphere mostly consists of a mixture of Nitrogen (about 70%) and Oxygen (about 30%). Both these gasses only store a small amount of heat from the sun.
There are smaller amounts of other gas in the atmosphere like carbon dioxide and methane. Both these gases hold a lot more heat compared with oxygen or nitrogen. During the last ice age there was less carbon dioxide in the atmosphere and the climate around the world was colder allowing vast ice sheets to cover Europe, North America and northern Asia.
Think about how large the Earth and its atmosphere are. People have burnt vast amounts of fossil fuel, removed many trees and caused other greenhouse gases to be released. The extra carbon dioxide, methane and other gases might be changing the Earth’s climate.
Major sources of carbon dioxide greenhouse gases include:
- Burning petrol and diesel for transport
- Burning coal to make electricity
- Clearing forests and burning the trees.