What WILL lead to humanity's demise? As Bill Gates says it won't be climate change, experts reveal the bleak reality of our extinction

In a surprising change of tone, Bill Gates has claimed that climate change 'will not lead to humanity's demise'.

Despite having spent vast amounts of his $122 billion net worth trying to fight climate change, the Microsoft founder now says world leaders should focus on other issues.

But if climate change isn't going to doom the human race, what will?

According to experts, the bleak reality is that humanity is much more likely to annihilate itself before the worst effects of climate change are felt.

From powerful AI models being created in labs around the world to devastating bioweapons, humanity is rapidly creating the tools of its own destruction. 

However, scientists who study so-called 'existential risks' believe that the biggest threat of all is the looming danger of total nuclear war. 

Dr Rhys Crilley, an expert on international relations from the University of Glasgow, told Daily Mail: 'The key difference is time: climate change unfolds over decades; nuclear war could end civilisation in the space of a few hours.

'Climate change is a slow-burning crisis that's already reshaping our world but will get worse in the future, whilst nuclear weapons pose the possibility of instant, total devastation for the planet.'

Will humanity destroy itself?

In an open letter ahead of the UN COP30 climate summit in Brazil, Bill Gates claimed that climate change was not the biggest threat to humanity.

Although the 70-year-old billionaire admitted that climate change would 'hurt poor people more than anyone else', he also argued that the 'doomsday outlook' was misguided.

He wrote: 'People will be able to live and thrive in most places on Earth for the foreseeable future.' 

However, although experts agree that climate change is not the biggest risk, there is some doubt as to whether humans will be able to 'live and thrive' into the future.

One of the biggest risks to humanity's long-term continuation is the threat of total nuclear war. 

What makes this so worrying is that the idea that these weapons could be used is no longer such a distant prospect.

Dr Crilley says: 'These risks are not theoretical: the weapons exist, the tensions between nuclear-armed states are worsening, and it seems that nuclear weapon states are increasingly willing to use force to get what they want whilst threatening to use nuclear weapons. 

'On top of this, we know that accidents and miscalculations happen, and that it was largely down to luck that there was no nuclear conflict during the Cold War.'

That is already a terrifying prospect, but research suggests that even a relatively contained nuclear war would spell the end of humanity. 

When atomic bombs detonate, they trigger enormous fires which inject columns of ash and dust into the atmosphere.

Just like the eruption of a supervolcano, this dust cloud would block out the sun for many years to come and cool the planet into a nuclear winter.

Using modern climate models, researchers have shown that a nuclear exchange would plunge the planet into a 'nuclear little ice age' lasting thousands of years.

Reduced sunlight would plunge global temperatures by up to 10˚C (18˚F) for nearly a decade, devastating the world's agricultural production.

Using modern climate models, researchers have shown that a nuclear exchange would plunge the planet into a 'nuclear little ice age' lasting thousands of years.

Reduced sunlight would plunge global temperatures by up to 10˚C (18˚F) for nearly a decade, devastating the world's agricultural production.

Studies suggest that 'small' engagement using just 100 warheads would collapse the global food system and cause an estimated two billion deaths by starvation in two years.

'There are over 12,000 nuclear warheads in the combined arsenals of the nuclear weapon states, so large-scale nuclear war would likely be an extinction event for the planet,' says Dr Crilley.

'It's clear to me that preventing nuclear war remains one of humanity's most urgent responsibilities.

Outside the risk posed by nuclear weapons, some researchers are also increasingly alarmed by the threat posed by engineered bioweapons.

Since 1973, when scientists created the first genetically modified bacteria, humanity has been steadily increasing its capacity to make deadly diseases.

Thanks to huge advances in AI, these modified bacteria or viruses are now even easier to create.

This potentially puts bioweapons in reach of technologically sophisticated terrorist groups or rogue states, massively increasing the risk.

Even an unintentional leak from a research facility has the potential to trigger a pandemic that far exceeds anything previously witnessed by humanity.

Otto Barten, founder of the Existential Risk Observatory, previously told Daily Mail: 'Although natural pandemics remain a very serious risk, this is very likely not going to cause our complete demise. 

However, man-made pandemics might be engineered specifically to maximise effectiveness, in a way that doesn't occur in nature. 

'The chance that ongoing democratisation of biotechnology leads to someone eventually trying and succeeding to create a pandemic that causes complete extinction is non-negligible.'

Is climate change an existential risk?

While Mr Gates is fairly certain that climate change will not destroy humanity, the experts are not so sure. 

Some researchers even argue that climate change should be considered an existential risk that ranks alongside the threat of nuclear war.

This is not necessarily because climate change could lead to a doomsday scenario, but because of how changing the climate tends to exacerbate other threats.

Dr SJ Beard, a researcher at Cambridge University's Centre for the Study of Existential Risk, told Daily Mail: 'There isn't a feasible climate scenario in which we all die of heat exhaustion or drown in the rising ocean. However, climate change can still kill us indirectly. 

'It can destabilise the geopolitical situation and cause World War 3, it can motivate people to engage in dangerous geoengineering experiments, it could trigger pandemics, or it could disrupt food and other supply chains enough to collapse the global economy.'

Climate change is now almost certainly going to have a massive impact on the world by increasing the intensity of extreme weather like droughts, flooding, and tropical storms.

Scientists believe this will create resource scarcity and lead to unprecedented levels of migration as people flee the worst-affected regions. 

In turn, this creates rising instability that could become the perfect breeding ground for conflict. 

Dr Crilley says: 'Climate change can heighten tensions between nuclear-armed states, as crises driven by droughts, floods, or food insecurity could easily interact with existing geopolitical tensions, making miscalculation or escalation of conflicts more likely.'

According to Dr Crilley, this 'absolutely' makes climate change an existential risk worth considering.