climate change

Change in the climate of an area or of the whole world over an appreciable period of time. A single winter that is colder than average does not indicate climate change; a change in average weather conditions from one period of time (for example, 30–50 years) to the next does indicate climate change. Climate fluctuations are natural phenomena, but there is increasing evidence to suggest that human industrial activity affects the global climate, particularly in terms of global warming.