Is There a Chance of an Existential Catastrophe Befalling Humanity?

In his book, the pre s, australian born oxford philosopher toby ord puts the chance of an existential catastrophe befalling humanity in the next 100 years at about one in six. He reaches this estimate by roughly adding up the odds of various existential catastrophes such as climate change, nuclear war and a super volcanic eruption,. But he does dress, don't take the estimates to be precise. Their purpose is to show the right order of magnitude, rather than o precise probability.