Green is powerfully associated with respect for environmental limits: whether in relation to climate change, biodiversity, water, land, oceans or their nexus interactions. It has carried many meanings in political and policy debates. The idea that one's society and economy are in urgent need of green transformation is beginning to take hold, albeit to varying extents, across political, policy and public debate. A fixation on global climate targets, and the particular forms of scientific and modelling knowledge they rest on, can marginalize alternative meanings, values and forms of knowledge around climate-related phenomena. Planetary boundaries offer a more recent and also more all-encompassing 'green limits' discourse. From the mid-2000s, scientists started to propose that people have entered a new epoch, the Anthropocene, in which human activities have become the dominant driver of many earth system processes including climate, bio-geochemical cycles, ecosystems and biodiversity. The extent of human influence has grown rapidly since the Industrial Revolution, accelerating dramatically since the 1950s.