evidence: The evidence of human influence on the climate system has strengthened progressively over the course of the previous five IPCC assessments, from the Second Assessment Report that concluded ‘the balance of evidence suggests a discernible human influence on climate’ through to the Fifth Assessment Report (AR5) which concluded that ‘it is extremely likely that human influence caused more than half of the observed increase in global mean surface temperature (GMST) from 1951 to 2010’ (see also Sections 1.3.4 and 3.3.1.1). The AR5 concluded that climate models had been developed and improved since the Fourth Assessment Report (AR4) and were able to reproduce many features of observed climate. Nonetheless, several systematic biases were identified (Flato et al., 2013). This chapter additionally builds on the assessment of attribution of global temperatures contained in the IPCC Special Report on Global Warming of 1.5°C (SR1.5; IPCC, 2018), assessments of attribution of changes in the ocean and cryosphere in the IPCC Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC; IPCC, 2019b), and assessments of attribution of changes in the terrestrial carbon cycle in the IPCC Special Report on Climate Change and Land (SRCCL, IPCC, 2019a).