He doesn't drink alcohol or smoke, which are good things when it comes to eking out your twilight years.

And despite reasonable concerns about his ravings - calling himself the "chosen one" and a genius, wanting to buy Greenland and nuke a hurricane away, saying he's the best in the world/history/ever on too many subjects to list and the whole "We fell in love" thing with Kim Jong Un - he's apparently not into drugs, also a point in your favour on the stayin' alive pendulum.

But he's obese, takes statins for high cholesterol, has coronary heart disease and, according to doctors' assessments of his published health profile in 2018, is at moderate risk of having a heart attack in the next three to five years.

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But he's still alive, and in the life expectancy stats game that makes him a winner, because when he was born in 1946 a white American male was only expected to live, on average, for about 63 years, according to the US National Centre for Human Statistics.

And he's very rich, which also gives him a rails run in the when-will-I-die stakes. By 2014 the life expectancy for a rich American man born in 1946 and living in New York had jumped to 86 years, or 23 years longer than that boy child could have expected to live on the day he was born.

And because it's America we're talking about, the land of the free and the brave that has one of the world's most disturbing levels of inequality, Trump can expect to live for 15 years longer than a man surviving at the lowest 1 per cent end of that country's socio-economic scale.

So stats-wise Donald Trump will probably make it to 2030, but not much more, meaning the spectre of a world that's two degrees Celsius hotter by 2050 would be theoretical for him, at best, even if he believed in climate change, which he doesn't.

Of course he says he believes in man-made climate change and the need to do something about it, sometimes. But like just about everything he says he walks his belief in man-made climate change back when the pressure's off, or he's at a Trump rally, or sitting in the early hours hurling out Twitter rants at perceived enemies.

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That's when he declares man-made climate change a "hoax", an "expensive hoax", "bulls..." and a "money-making industry". That's when he sort-of accepts the world will heat up but offers that "it will change back again" as a reason for dismissing the whole thing.

That's when he reverts back to his November 6, 2012, Twitter rant that "The concept of global warning was created by and for the Chinese in order to make US manufacturing non-competitive".

That's when we know why America pulled out of the Paris Agreement, and why Trump attended a United Nations religious freedom event in New York this week while a teenage girl only metres away cut through with a speech whose moral force crystalised with the words "How dare you".

Trump claims to have a "natural instinct for science".

It's the "natural instinct" that produced this gem from the world's most powerful and influential man, who remains just as powerful and influential despite an impeachment process that finally started rolling out this week: "If you have a windmill anywhere near your house, congratulations, your house just went down in value by 75 per cent. And they say the noise causes cancer".

It's that "natural instinct for science" that also produced my personal favourite Trumpian science rant - his outrage in 2015, before he was president, that climate change talk could stand in the way of his God-given right to use hair spray.

During a campaign speech in South Carolina Trump criticised US President Barack Obama for worrying too much about "the carbon footprint" of greenhouse gas emissions causing climate change, and threw in a bit about the hole in the ozone layer just to confuse things a little.

"I want to use hair spray," said Trump to the South Carolina crowd on December 30, 2015, and the crowd roared, although a few of the boofiest blokes in the back rows avoided each other's eyes and kept their heads down for a bit, beneath their "Make America Great Again" caps.

Hair spray? they thought. A man using hair spray? But Trump raved on.

"They say, 'Don't use hair spray, it's bad for the ozone'. So I'm sitting in this concealed apartment, this concealed unit... It's sealed. It's beautiful. I don't think anything gets out. And I'm not supposed to be using hair spray?" he ranted, before his attention wandered elsewhere.

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Young people around the world have responded to teenager Greta Thunberg's remarkable calls for action. Millions have taken to the streets in the past week to demand their right to a future where a warming world is at least contained at a level before catastrophic impacts.

Thunberg is only slightly older than Trump's youngest, Barron. But even an appeal to Barron's future doesn't move a man like Trump, whose sarcastic tweet describing Greta Thunberg as "a very happy young girl looking forward to a bright and wonderful future", was rightly condemned, while her response was praised.

Trump is the self-interested, self-focused, arrogant, ignorant powerful man who will be dead when the Greta Thunbergs of this world are dealing with the consequences of - her words - "the fairytales of eternal economic growth" as the world warmed.

It was fitting that Trump - the president who tried to ban all Muslims from entering America - spruiked religious freedom to a hypocritical evangelical Christian crowd this week and honoured "the eternal right of every person to follow their conscience".

Greta Thunberg and millions of others are.

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