When the Paris Agreement in December 2015 called for the IPCC to put together a “Special Report” on Global Warming of 1.5°C, scientists knew very little about the exact differences that half a degree makes (1.5°C versus 2°C). Never before have so many independent studies been conducted at such short notice, in order to meet this pressing question of the global climate negotiations community. Is a warming of 2°C above pre-industrial levels sufficiently low a limit to avoid dangerous anthropogenic interference with the climate system, and, if not, can we implement a lower limit?