A nuclear war expert who claims we are getting closer to atomic warfare says it would take 72 minutes to wipe out five billion people if the worst comes to pass.

Investigative journalist Annie Jacobsen, from Connecticut, who is a New York Times bestselling author, and a 2016 Pulitzer Prize finalist, joined Steven Bartlett on The Diary of a CEO podcast just how close we are to nuclear war.

Since she started writing her book Nuclear War: A Scenario, in 2020 she said: 'The geopolitical temperature of the world has escalated to a point that you have not seen in your lifetime and I haven't seen in my lifetime.'

In the month that her book was published Russian president Putin moved nuclear weapons into Belarus, claiming it is a precautionary measure for 'anyone thinking of inflicting a strategic defeat' on Russia.

Annie said: 'If a nuclear exchange happens - and we're talking strategic ballistic missiles - it will not stop until the world ends and we are talking about in seconds and minutes not in days and weeks and months.' 

Nuclear war expert Annie Jacobsen, from Connecticut , US, revealed we are getting closer to atomic warfare on The Diary of a CEO podcast

Annie, who interviewed former secretaries of defense, a former nuclear sub Commander and a former cyber Chief, revealed they all said that 'the nuclear threat is always there.'

She said: During the previous administration, former president Trump, there was this presidential rhetoric going on, you may recall - fire and fury Trump and the leader of North Korea threatening this kind of thing. And like many I'm sure began to wonder, "My God what if deterrence, another word for prevention, fails?" and that is the question that I put to all of those sources in the book.'

The investigative journalist went on to explain that the president of the United States has 'sole presidential authority to launch a nuclear weapon.'

She said: 'What does that mean? It's exactly like it sounds, it's "solo presidential". He's the POTUS authority. He doesn't have to ask anyone for permission not the SEF, not the chairman of the Joint Chiefs of Staff, not the Congress.'

Explaining why this power would be given to just one person, she explained: 'It has to do with the ticking clock of it.'

'An ICBM (intercontinental ballistic missile) travels from one continent to the next in roughly 30 minutes carrying a nuclear warhead to strike a target.

'There are only 30 minutes, this isn't like, "Hey guys should we go have a war in Iraq. Let's discuss this, let's debate", this is: "There is a ballistic missile sir coming at the United States and you must act" and that's why, in the simplest layman's terms, sole presidential authority exists.'

Annie, who is a New York Times bestselling author, and a 2016 Pulitzer Prize finalist, joined Steven Bartlett (pictured) on The Diary of a CEO podcast just how close we are to nuclear war 

Since she started writing her book Nuclear War: A Scenario, in 2020 she said: 'The geopolitical temperature of the world has escalated to a point that you have not seen in your lifetime and I haven't seen in my lifetime'

Annie revealed she wanted to write the book because people have become complacent about the threat of Nuclear Wa,r and some may not even know what that would mean to their lives. 

She said: 'I wanted to show in horrific detail just how horrible, just how apocalyptic nuclear war will be because I think many people have forgotten, or don't know to begin with, the consequences of a nuclear exchange.'

Annie sourced information from defense department documents and defense scientists to be able to determine precisely what happens during a nuclear attack. 

She said: 'On top of the initial flash of thermonuclear light, which is 180 million degrees, which catches everything on fire in a nine mile diameter radius; on top of the bulldozing effect of the wind and all the buildings coming down and more fires igniting on top of the radiation poisoning people to death in minutes and hours and days and weeks, if they happen to have survived, on top of all of that, each one of these fires creates a mega fire that is 100 or more square miles and so.'

The author said if the world went into nuclear war you would 'want to die instantly' because 'there is no more law and order.'

She said: 'There's a quote from Nikita Khrushchev, the first secretary of the Communist Party of the Soviet Union, he said: '"After nuclear war the survivors would envy the dead".

'Who's left? It's man returning to the most primal, most violent state as people fight over the tiny resources that remain, and by the way they're all malnourished, everybody's sick and most people have lost everything and everyone they know. How's that going to feel?' 

Elsewhere Annie revealed North Korea has launched more than 100 ballistic missiles in an 18-month period from 2022. Although they were tests she said other nations inform each other when they're going to test so it doesn't cause anxiety and confusion.

She said: 'North Korea doesn't adhere to that. All of that command and control is focused on, "Is this coming at us?". North Korea don't announce those tests and so imagine the anxiety in those command bunkers every time they launch a ballistic missile.

'This is so dangerous and so rogue. On one hand I say there are no rules to nuclear war, but there are a few nuclear rules to nuclear deterrence, like you tell neighbours.'

If nuclear war did break out Annie said the safest place to be would be in Australia or New Zealand because of the agricultural resources.

She said: 'Agriculture would fail and when agriculture fails people just die and on top of that you have the radiation poisoning because the ozone layer will be so damaged and destroyed that you can't be outside in the sunlight and so people will be forced to live underground - fighting for food everywhere except in New Zealand and Australia.'