Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain
the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in
Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles
Climate change refers to a statistically defined change in the average and/or variability of the climate system; this includes the atmosphere, the water cycle, the land surface, ice and the living components of Earth. The definition does not usually require the causes of change to be attributed, for example to human activity, but there are exceptions.