Dr Lauren Holt and Dr Simon Beard were commissioned by the BBC to write an introduction to existential risk.
"Human extinction may be the stuff of nightmares but there are many ways in which it could happen.
Popular culture tends to focus on only the most spectacular possibilities: think of the hurtling asteroid of the film Armageddon or the alien invasion of Independence Day.
While a dramatic end to humanity is possible, focusing on such scenarios may mean ignoring the most serious threats we face in today's world. And it could be that we are able to do something about these.
Volcanic threats
In 1815 an eruption of Mount Tambora, in Indonesia, killed more than 70,000 people, while hurling volcanic ash into the upper atmosphere.
It reduced the amount of sunlight hitting the surface of the Earth, triggering what has become known as the "year without a summer".
Lake Toba, at the other end of Sumatra, tells a still more sinister story. It was formed by a truly massive super-volcanic eruption 75,000 years ago, the impact of which was felt around the world.
It has been suggested that the event led to dramatic population decline in early humans, although this has recently been questioned.
But while the prospect of a super-volcanic eruption is terrifying, we should not worry too much. Super-volcanoes and other natural disasters, such as an asteroid striking Earth or a star exploding in our cosmic neighbourhood, are no more likely in 2019 than any other year. And that is not very likely.
Growing threats
The same cannot be said for many global threats induced by people. For example, the World Health Organization and the World Economic Forumboth listed climate change and its effects as one of their top risks for 2019.
Recent UN talks heard climate change was already "a matter of life and death" for many regions. While many, including Sir David Attenborough, believe it could lead to the collapse of civilisations and the extinction of "much of the natural world".
The threats are complex and diverse, from killer heatwaves and rising sea levels to widespread famines and migration on a truly immense scale.
Also increasing are the potential risks from novel technologies such as artificial intelligence (AI). The scenarios range from increasingly sophisticated cyber-weapons that could hold an entire nation's data to ransom, to autonomous algorithms that could unwittingly cause a stock-market crash.
Another threat is the possibility of a nuclear war. While many focus on rising tensions between global powers, new technologies may also be making us less safe. This is because of both the "entanglement" of nuclear and conventional weapons and the risk that AI could help unleash nuclear war."
