e.g., changes in global mean temperature and sea level. In the TAR, the word "projection" is favoured over "prediction". This is because many future changes related to climate are highly uncertain. For example, climate change projections are affected by highly uncertain changes in future GHG emissions.

The TAR projects impacts according to possible future changes in global mean temperature. Other projections are based on scenarios that the IPCC has developed. In 2000, the IPCC published