Over the years, the UNFCCC and its 197 parties benefited from the assessment reports of the IPCC as a basis for negotiation and to underline the need for progress. The material in AR2 supported the adoption of the Kyoto Protocol while the 2007 AR4 focused on limiting warming to 2°C, a target also mentioned in the Copenhagen Accord. By the fifth assessment report (AR5), the underlying science was able to identify causal links to a high certainty and included projections underlining key risks due to climate change impacts. The publication of AR5 during 2013 and 2014, and the projections therein, provided a solid foundation to advance towards adoption of the Paris Agreement at COP21 in Paris in 2015. On the same occasion, the UNFCCC requested a special report from the IPCC on ‘the impacts of global warming of 1.5°C above pre–industrial levels and related global greenhouse gas emissions pathways’, which was delivered in 2018, as seen in the timeline below.