Climate change is a change of climate attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods
Climate change encompasses all forms of climatic inconstancy (that is, any differences between long-term statistics of the meteorological elements calculated for different periods but relating to the same area) regardless of their statistical nature or physical causes
National Snow and Ice Data Centre
Climate change or variability refers to variations in the mean state and other statistics (such as standard deviations, statistics of extremes, etc.) of the climate on all temporal and spatial scales beyond that of individual weather events. Variability may be due to natural internal processes within the climate system (internal variability), or to variations in natural or anthropogenic external forcing (external variability)
Colorado Water Conservation Board
Climate change is any long-term change in the patterns of average weather of a specific region or the Earth as a whole. Climate change reflects abnormal variations to the Earth's climate and subsequent effects on other parts of the Earth, such as in the ice caps over durations ranging from decades to millions of years.
Climate change: long-term alteration in global weather patterns, especially increases in temperature and storm activity, regarded as a potential consequence of the greenhouse effect
Climate change represents a change in these long-term weather patterns. They can become warmer or colder. Annual amounts of rainfall or snowfall can increase or decrease.
US EPA, Climate Change Kids Site
Climate change term is sometimes used to refer to all forms of climatic inconsistency, but because the Earth's climate is never static, the term is more properly used to imply a significant change from one climatic condition to another.
California Climate Change portal
Climate change: The periodic fluctuations in global temperatures and precipitation, such as the glacial (cold) and interglacial (warm) cycles of the Pleistocene (a geological period from 1.8 million to 10,000 years ago)
The Free Dictionary
Climate change theory emphasizes an expected change in magnitude of radiation processes as an outcome of changing concentrations of anthropogenic greenhouse gases and leads to flawed conclusions
Climate Change: A Natural Hazard by William Kininmonth
Climate Change — Changes in regional climate characteristics, including temperature, humidity, rainfall, wind, and severe weather events.