What happens when the AMOC collapses?

Sometimes, I just wish scientific researchers would just come out with their best guess.

I know why they don’t. Look at what happened with covid. Not every best guess made while the bodies were still piling up in coolroom trucks in hospital carparks turned out to be dead on. Who would have thought? And every uncertainty or consequence couched in terms of risk is latched onto and exploited by bodies with a powerful incentive to keep on doing business as usual till the world burns up. So we get this very cautious framing in terms of probabilities that just doesn’t make for rivetting reading.

But it’s a pity. I know climate models are unbelievably complex, but I’d really like more informed best guesses about what the AMOC collapse is likely to do. I get the big picture, but that was why I wrote ‘470’ – sometimes the big picture is just too big to bring it into focus.

For instance, we know it’s not something so far in the future our grandkids will be the ones dealing with it – we know it’s already slowed and could collapse completely any time, more likely sooner than later and sooner could be as soon as next year.

We know it’s a climate tipping point and it’s irreversible in human timeframes. We know it’s going to have profound effects on how heat and moisture move around the planet. And that’s going to have profound effects on crops and food prices, heating and cooling, bushfires, droughts, floods, diseases, economies, famines, wars and refugees. Smart people would be filling in one of those WHS Hazard and Risk matrixes and racing to get set up to adapt. (Well, smart people would have acted before now so as not to have to adapt, but there you go).

I’d like a few more hints about how to be smart.

That deep blue up in the right hand corner of the map? That’s extreme cold, where the circulation of warm water (and the warm air over it) that has made western Europe so benign for humans … just stops. The numbers being thrown around are 10 degrees C or more cooler, not for a day or two but on average, for good, and all that part of the world is already stuggling to find ways to warm homes and buildings over winter. The war in Ukraine, the geopolitics of gas mining …

And see all that orange in the southern hemisphere? That’s warm sea surface temperatures, big oceans massively warming. Melting Antarctic ice. Changing the speed of trade winds, the way that the El Niño-Southern Oscillation (ENSO) cycle works, the Indian Ocean dipole, the strength of cyclones, the path of monsoonal rain.

The best guesses I can find about what we Australians might need to deal with in direct climate effects are hotter weather, stronger cyclones, a monsoonal rain pattern that moves south, (making it relevant not just to Darwin and far northern Australia but to Queensland and northern NSW too), a lower frequency of strong El Niño and more La Niña – which is good news for the eastern states as far as bushfires go but bad news for flooding.

And then there’s all the indirect effects – economic impacts, refugees, supply chains, energy policies.

For me? Think even more about resilence in the face of economic shockwaves, wet bulb heatwaves, and floods in my own communities. And campaign even more strongly for real resistance to the pushers who are trapping so much of the world in addiction to climate crashing substances.

(The map comes from this PhD thesis, and I found it useful for trying to understand it all, if you want to go beyond journalism sources: https://unsworks.unsw.edu.au/entities/publication/d6fafe02-4da5-4102-a2d3-bf47bf388b7b/full)