Climate Change refers to "any change in climate over time, whether due to natural variability or as a result of human activity".
(IPCC)
Remark:
For the UNFCCC, climate change refers to a change of climate that is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparable periods.
This is equivalent with the notion of "anthropogenic climate change".
=> Glossary