This column, I'll admit, is prompted by an article in Thursday's Australian Financial Review by Canberra journalist and former Washington correspondent Jacob Greber.

The article, an analysis piece, was titled Reality check for Morrison and Taylor's golden ticket to net zero, and one of the sources it quoted was Professor Kenneth Baldwin, a physicist and director of an Australian National University "grand challenge" initiative: Zero-Carbon Energy for the Asia Pacific.

Professor Baldwin's work grabbed Greber's attention for the same reason his article grabbed mine.

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It put into plain English the scale of the industrial overhaul - another industrial revolution no less - that is needed if the world is to abandon fossil fuels and go down the renewables path and try to maintain the same sort of modern style of living we enjoy here in the West.

Baldwin has done some sums on what it would take to replace Australia's existing energy exports - dominated by thermal coal (exported from Newcastle) and liquid natural gas (shipped from Queensland, Northern Territory and Western Australia) - and replace them with 20 per cent renewably generated electricity and 80 per cent hydrogen.

And he's thrown in our steel and aluminium exports as well, but as "green" steel, and aluminium made using renewable electricity.

The answer, Baldwin says, is 168,000 square kilometres of wind and solar farms, producing 27 times the amount of electricity our national grid does today.

That land mass, Greber notes, is two-thirds the size of New Zealand. I checked some other countries, and it's much bigger than Greece, at 132,000 square kilometres, and about the size of Uraguay (176,000 square kilometres) minus Cyprus (9200 square kilometres).

Baldwin - who is not a back-of-the-envelope nutter like me, but an award-winning physics professor - a rightly describes such numbers as "huge".

They are so big, that they're a reason I didn't write about another analysis doing the rounds a little while back.

I have written before about the sheer scale of the task involved in replacing coal, and asked whether the politicians truly understand the magnitude of the changes they seem to think we will take in our stride.

The presentation sent to me says that replacing the state's coal-fired power stations would require 3000 wind turbines costing $25 billion, 50,000 hectares of solar panels costing $25 billion and 90,000 megawatts of batteries costing $90 billion, at a total cost of $140 billion.

Then there's hydrogen - the ultimate example of the "future technologies" that the Morrison government has been repeatedly accused of hiding behind in its net-zero by 2050 plan.

It's yet to be produced commercially in anything like the quantities that will be needed to make inroads into fossil fuel demand, and then at a much higher price than the "$2 a kilogram" the PM and others are breezily bandying about.

The most likely method of making hydrogen is to split water molecules (H20) using electrolysis.

The head of the Australian Renewable Energy Agency (ARENA), Darren Miller, said last year that $2 hydrogen would need electrolyser costs to fall from between $2 and $3 million per megawatt to $500,000 per megawatt, and the cost of solar and wind electricity to "nearly halve" from today's levels.

And that's without infrastructure to store and transport a fuel that is both notoriously explosive, and evaporative, or "leaky".

I'm not saying it's impossible.

We are where we are - in both the good and bad senses - because of our technological abilities.

And even if the world is awash with debt, the money supply is being constantly expanded.

We'll need it.

A recent Bank of America report put the cost of decarbonising to reach net zero at $US5 trillion - that's $5000 billion - a year, every year, for the next 30 years.

Given the world gross domestic product or GDP is likely to top $US90 trillion this year, that $5 trillion a year is about 5.5 per cent of GDP, or more than twice the 2 per cent that most Western nations spend on defence.

At least we have plenty of land in Australia.

Much more than New Zealand (whether or not it's covered in wind turbines and solar farms).

This week the West Australian government proposed changes to land tenure laws it says will unlock "millions of hectares" for wind and solar farms and hydrogen production.

Perhaps just in time.

Just before Glasgow, iron ore billionaire Andrew "Twiggy" Forrest unveiled a proposal for a green hydrogen plant at Bell Bay in Tasmania.

On Thursday, former Greens Tassie senator Bob Brown let fly against the idea, with full-page ads saying "let's come down to earth and take the 'hydro' out of hydrogen".

It's an old joke, I know, but as Kermit says, it's just not easy being green, is it . . .

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