The global catastrophic risks in this report can be divided into two categories. Some are ongoing and could potentially occur in any given year. Others are emerging and may be very unlikely today but will become significantly more likely in the coming decades. The most significant ongoing risks are natural pandemics and nuclear war, whereas the most significant emerging risks are catastrophic climate change and risks stemming from emerging technologies. Even where risks remain in the future, there are things we can do today to address them. ... The relative likelihood and urgency of the different risks matters when deciding how to respond. Even though the level of uncertainty is extreme, rational action requires explicit assessments of how much attention the different risks deserve, and how likely they are. The views of the authors on these vexed questions, based on our reading of the scientific evidence, are summarised in the following table. More information can be found in the full version of this report.