"Dreaming the impossible" is a phrase we've all heard. As a motivating slogan, it's not bad. After all, we humans are pretty amazing. What we've done over the past century or so has been astounding.
Take going to the moon, the subject of the new movie First Man starring Ryan Gosling as Neil Armstrong — what better example of dreaming the impossible?
On the flip-side, though, dreaming the impossible can be, well, delusional. Something may indeed be impossible, for good scientific reasons.
There's an impossible dream we all — but especially governments — need to give up on, and quickly. Which is that we can tackle global warming and continue to grow the world's economy.
The impossibility of doing both becomes clear if we crunch some numbers.
2050 is often cited as the year by which the world needs to have basically stopped using fossil fuels.
And yet over this same period, governments will be expected to pursue policies which deliver 2-3 per cent growth per year — the average range that keeps global investors, banks and business lobbyists happy.
Let's say growth was 2.5 per cent each year until 2050. That would leave us with a world economy more than twice the size it is now.
Think about what that means in terms of goods and services produced, the infrastructure needed to sustain all that economic activity, twice what exists presently on a global scale.
And think about the increase in energy needed to power our vehicles, homes, factories, farms and increasingly our data (the internet consumes a lot of energy).
Now consider that in 2016, only 5 per cent of the world's energy came from renewables (a big chunk of that from hydro dams built decades ago). Ten per cent came from biofuels and 5 per cent nuclear. The rest, a whopping 80 per cent, came from burning fossil fuels (oil, gas and coal).
Taking fossil fuels out of the equation creates a massive energy deficit.
And the inconvenient truth is that our alternative energy sources — solar, wind, tidal, biofuels or nuclear — aren't up to the task of making up that deficit, especially for a growing economy.
All other options have material and cost limitations that will restrict their "upscaling".
As storers of potent and transportable energy, oil, gas and coal are just too good. Which is why we've gorged ourselves on them and created a global society of incredible complexity and wealth, even if that wealth hasn't been fairly distributed.
Maybe we can avert the worst effects of global warming (I'll give us a 50/50 chance), but we won't be doing that and expanding the world's economy.
Believing the impossible dream of endless economic growth on a planet with finite resources is delusional.
And yet this is what our politicians are expected to believe. No wonder Jacinda Ardern is getting herself in such a tangle.
She talks about growth one day, cutting carbon emissions the next. It's an impossible political position she's staked for herself. Though she's far from the only politician around the world who's done so.
The urgency of the climate change threat means we need political leaders brave enough to talk about the end of economic growth.
They'll be attacked mercilessly for it from some quarters, but many more of us will appreciate an honest appraisal of the situation we're in.
■ Vaughan Gunson is a writer and poet interested in social justice and big issues facing the planet.