This chapter builds on findings of the AR5 and assesses new scientific evidence of changes in the climate 4 system and the associated impacts on natural and human systems, with a specific focus on the magnitude and 5 pattern of risks for global warming of 1.5°C above the pre-industrial period. Chapter 3 explores observed 6 impacts and projected risks for a range of natural and human systems with a focus on how risk levels change at 1.5oC and 2o 7 C. The chapter also revisits major categories of risk (Reasons for Concern) based on the 8 assessment of the new knowledge available since the AR5.