“Climate change refers to a change in the state of the climate that can be identified (e.g. using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. (...) It refers to any change in climate over time, whether due to natural variability or as a result of human activity.”
Source: IPCC. 2007. "Climate Change 2007: Synthesis Report". Intergovernmental Panel on Climate Change (IPCC). <https://www.ipcc.ch/site/assets/uploads/2018/02/ar4_syr_full_report.pdf>. Accessed 10 June 2020.