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Comment by mschild | Hacker News Reader

An article from livescience.com that may be worth a read.

TLDR: if slowdown occurs, temperatures could drop by 5C in Europe and North America. What a 5C drop actually looks like they don't say.

https://www.livescience.com/planet-earth/climate-change/gulf...

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I suppose that energy still has to go somewhere. Which place will warm up if Europe and North America cool down?

I'm not a climate scientist but I'd reason that the tropics would experience greater heating resulting from the stagnation of the warm water that would previously circulate. More warm water in the tropics would result in more frequent and more intense hurricanes, so if the AMOC stops then we'll see even more extreme weather records smashed.

Obviously, the Atlantic Ocean closer to the equator.

Pretty sure Europe will heat up, NA will cool down. Currently the Atlantic current brings hot water from the equatorial zones up the US east coast, hence the humidity there. And it brings cool water down from the Arctic to Europe’s west coast, hence the mild non-humid climate there. Reversing the current would reverse that dynamic. It might make Europe less suitable to wine growing, for one, which requires mild cool climates.

The current wouldn't reverse, it would stop or become a lot slower. So cold water would stay in the artic regions and warm water closer to the equator.

I suppose you could compare this to one giant heat pump, circulating a heat source to Europe and North America that makes life livable.

As I understand it, the warmer the water, the stronger and more powerful the hurricane. So bigger and more hurricane in the mid-latitudes (Caribbean, southern US). Not a good prospect, at all.

Isn't it the opposite? I was under the impression that warm water from the Caribbean / equitorial zones was currently brought over to Western Europe and the UK.

If the AMOC collapses, that heat will presumably stay in the tropics, and North Western Europe will cool.

> I was under the impression that warm water from the Caribbean / equitorial zones was currently brought over to Western Europe and the UK.

It does after it's gone north along the US East coast yes, then it crosses over to Europe, but it's obviously not as hot anymore having dumped some of its heat into the US and the North Atlantic.

There's no current that goes directly from the equatorial regions straight up to the west coast of Europe.

How does that 5C drop interact with the rise that we're currently concerned about? (Heatwave, wildfires in the med etc).

I'm guessing it's hopelessly naive to assume it'll just... kinda cancel each other out?

The net energy of the system will remain the same, just distributed somewhere else.

the net energy of the system will not remain the same if we keep inputing at a non negatable rate

Erratic is what you can expect (and are already getting)

I'd expect averages might drop in spots, and raise in others, regionally. But the variance will be all over the map. And already is.

Summer heat waves, droughts, intense tropical storms.

And then winters with unusually warm days followed by record lows.

For Northern/Western Europe, with the gulf stream interrupted I'd imagine the could expect a climate closer to what the northeast of the Americas already get: erratic inconstant weather patterns with lower lows than they're used to.

Remember that the northeast and midwest is quite a bit further south than many western & northern European cities, but suffers far more brutal winters.

Here in southern Ontario, we're at the same lattitude as northern Italy or south of France, and our summers can be just as hot, and growing season about as long (and way more humid). ... But in the winter there's episodic lows below -25C, -28C. And I can tell you, you can't easily grow e.g. vitis vinifera grapes with those patterns, and certainly not figs, citrus, etc.

I don't think Europeans are mentally prepared for this, if it's coming.

I would guess we'll see steeper gradients which means more extreme weather.

At this point we can’t even manage 0.1C, how are we going to get 5C?

Over what timeframe?

Edit: a decade.

So if this continues it will result in a 5C drop in temprature across North America and Europe? Am I understanding this correctly.

Which for reference a 5C drop should mean that New York is covered in glacier according to this source https://xkcd.com/1732/

NYC was covered in a glacier the last time the global average temperature was 5C cooler.

That's not the same thing as Europe and NA cooling by 5C.

While strictly true, that doesn't mean 5C cooling wouldn't eventually result in NYC under ice.

You've misunderstood the source. While temperatures locally will drop by 5C, the global average will not.

That chart shows global averages, ie, the whole world was 5C colder. NY might have been much, much colder than that.

The Ave Temp of the world is rising and from what I read and hope I understood, nothing will really stop that, all we can do is hope to lessen the temp rise.

So, I think this "5C" drop in East NA and West Europe will be absorbed throughout the world. So those regions will still have higher ave temp then say 1950, just a bit less than the rest of the world.

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