1. An influence that is relevant for determining the climate state in a region; much the same as climatic control, but regarded as including more local influences, such as the effects on the climate of local aerosol loading or extensive paving in or near a city. 2. An influence that has a major effect on human activities or human history. For example, it has been suggested that climate change may have been a factor in the disappearance of the Anasazi culture in the North American southwest.