Humanity could be wiped out by “catastrophic” climate change within 100 years.

That’s the terrifying claim from a top scientist who believes there is a one in 20 chance that our species will go extinct by the end of the century thanks to “low-probability high-impact” events.

Veerabhadran Ramanathan, a professor of climate and atmospheric sciences at the University of California, performed a series of calculations to work out what would happen if temperatures rose between now and 2100.

He found that an increase greater than 3 degrees Celsius could lead to “catastrophic” effects, but an increase of more than 5 degrees Celsius results in “unknown” consequences which could lead to the end of humanity.

“When we say five percent-probability high-impact events, people may dismiss it as small but it is equivalent to a one-in-20 chance the plane you are about to board will crash,” said Ramanathan.

“We would never get on that plane with a one-in-20 chance of it coming down but we are willing to send our children and grandchildren on that plane.”

If the planet warms up, the consequences could include an increased risk of deadly weather events such as killer heat waves, hurricanes, floods or droughts.

Soaring temperatures could trigger “tipping points” such as rising sea levels caused by the collapse of the West Antarctic Ice Sheet, which would result in the flooding of many of the world’s most important cities.

The effects will be particularly grim for the poor, who will not be able to simply up sticks and move if their home is ravaged by extreme weather conditions.

These grim predictions are based on calculations suggesting temperatures will shoot up by between 3 degrees Celsius and 5 degrees Celsius.

Ramanathan said there was a risk of temperatures rising even higher, with “unknown” consequences for humanity and the planet.