Comment by hedora | Hacker News Reader

Comment by hedora | Hacker News Reader

This is a long article, and they take a long time to summarize their conclusions:

> In other words: we are talking about risk analysis and disaster prevention. This is not about being 100% or even just 50% sure that the AMOC will pass its tipping point this century; the issue is that we’d like to be 100% sure that it won’t. That the IPCC only has “medium confidence” that it will not happen this century is anything but reassuring, and the studies discussed here, which came after the 2021 IPCC report, point to a much larger risk than previously thought.

There are some maps towards the bottom of the article. To summarize: If the Atlantic currents do collapse, Europe will likely be covered by a glacier. Fossil records and computer models agree this could happen in our lifetimes. I first heard the alarm being sounded over this in the 1990’s (based on fossil records).

The last time this happened the process took 50-100 years to flip Europe from normal to ice age.

> If the Atlantic currents do collapse, Europe will likely be covered by a glacier.

I think you misread the article here. Looking at Figure 15 (temperature change caused by a total AMOC collapse), it appears that Britain, Iceland, Scandinavia etc. would cool by around 2°C, whereas the rest of Europe warms by roughly the same amount. The consequences of such a strong temperature gradient are worryingly hard to predict, but don’t involve Europe being ‘covered by a glacier’. (Scandinavia, maybe? But not most of Europe.)

Is that 2 degrees of cooling gross or net the predicted warming? i.e. is that 2 degrees below pre-industrial levels, or is it x-2 where x is warming due to global warming ≈ about pre-industrial levels.

The last time this happened, the glacier reached France and Germany.

Looking at the figure caption, it appears to be relative to the simulated temperature without doubled carbon dioxide concentration and AMOC breakdown.

IMHO you left out one very important sentence just before the part you've quoted:

"A full AMOC collapse would be a massive, planetary-scale disaster. We really want to prevent this from happening."

And uncertainty here is not if it will ever happen - we know it will eventually, if the temperature continues to rise - part we're unsure of is only whether it will happen before 2100, or later.

Which makes the following part of the text a real conclusion for me:

"For the AMOC and other climate tipping points, the only action we can take to minimize the risk is to phase out fossil fuel use and stop deforestation as fast as possible. If we can reach zero emissions, further global warming will stop within years, and the sooner this happens the smaller the risk of passing devastating tipping points. It would also minimize many other losses, damages, and human suffering from “regular” global warming impacts (e.g., heatwaves, floods, droughts, harvest failures, wildfires, sea level rise), which are already happening all around us even without the passing of major climate tipping points."

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