Causes of changes to different aspects of the climate system are attributed to human and/or natural influences.
Observations contain information about how climate has varied. Climate models provide the facility to investigate the impact of different influences on climate, including both anthropogenic and natural factors, and to determine the level of variability that would still exist in the climate system even if these did not change.
In this area of work, observations, climate models and advanced statistical methods are brought together with the aim of determining if the changes that are observed in the climate system can be attributed to natural or anthropogenic causes, or both. The result is a robust statistical assessment of whether anthropogenic influences on our climate can be detected and attributed given our current knowledge.