Planetary boundaries are those considered crucial to maintaining an environment in which humanity can safely exist.
Nobel Prize-winning atmospheric chemist Paul Crutzen, US climatologist James Hansen and Johan Rockstrom from the Stockholm Resilience Centre, developed an analysis of nine of these boundaries some years ago.
Alongside climate change, they include ocean acidification, ozone depletion, fresh water use, change in land use, biodiversity loss, chemical pollution, atmospheric aerosol loading and the nitrogen and phosphorous cycles.