Thanks for writing this. The impacts of an AMOC collapse on the food-system implications are definitely worth studying. However, as written the post seems to exaggerate the risk somewhat.
1. The post mixes the impacts of an AMOC collapse in isolation (eg the Jackson paper), with its impacts embedded in a warming world (one of the papers you cite estimates the effects may just cancel). The latter seems more relevant here
2. I also agree with the previous comment that you seem overly drawn to the sudden shutdown literature. There’s a lot of literature on this topic, and it’s probably best to start with the IPCC estimate and update from there.
[More specifically, the higher probability papers you cite generally rely on early warning indicators increasing in variance prior to collapse. This assumes 1. The indicators are highly predictive (which is debated) and 2. That increases in variance are associated with imminent tipping points. The IPCC characterizes the latter as “low confidence” because the same metrics also rise in unforced scenarios.]
Again, not saying this isn’t worth studying, just adding some caution. Happy to talk more if helpful.
That increases in variance are associated with imminent tipping points. The IPCC characterizes the latter as “low confidence” because the same metrics also rise in unforced scenarios.
What about autocorrelation? I [edit: mistakenly] think Ditlevsen & Ditlevsen themselves identify this as a stronger warning sign than variance.
AR6 doesn’t comment on autocorrelation (see section 9.2), but the paper actually identifies the variance as a stronger signal: “Here we establish such a measure of the confidence for the variance and autocorrelation and demonstrate that variance is the more reliable of the two.”
Thanks for your comment! I’m actually attending the Global Tipping Points Conference right now, and the leading scientists still say there are mixed results regarding net temperature change in post-collapse scenarios and that overall change hides what could be very different summers and winter results. It very much depends on how much warming we have already experienced at the time of a potential AMOC collapse, as well as the state of other interconnected regional climate systems—like the ice sheets. Suffice it to say it’s tough to model. I think it’s fair to say, though, that it wouldn’t just “cancel out,” as there are the ITCZ shift, the monsoon changes, Northern Hemisphere drying, and other knock-on effects outside of surface air temperature.
Thanks for writing this. The impacts of an AMOC collapse on the food-system implications are definitely worth studying. However, as written the post seems to exaggerate the risk somewhat.
1. The post mixes the impacts of an AMOC collapse in isolation (eg the Jackson paper), with its impacts embedded in a warming world (one of the papers you cite estimates the effects may just cancel). The latter seems more relevant here
2. I also agree with the previous comment that you seem overly drawn to the sudden shutdown literature. There’s a lot of literature on this topic, and it’s probably best to start with the IPCC estimate and update from there.
[More specifically, the higher probability papers you cite generally rely on early warning indicators increasing in variance prior to collapse. This assumes 1. The indicators are highly predictive (which is debated) and 2. That increases in variance are associated with imminent tipping points. The IPCC characterizes the latter as “low confidence” because the same metrics also rise in unforced scenarios.]
Again, not saying this isn’t worth studying, just adding some caution. Happy to talk more if helpful.
What about autocorrelation? I [edit: mistakenly] think Ditlevsen & Ditlevsen themselves identify this as a stronger warning sign than variance.
AR6 doesn’t comment on autocorrelation (see section 9.2), but the paper actually identifies the variance as a stronger signal: “Here we establish such a measure of the confidence for the variance and autocorrelation and demonstrate that variance is the more reliable of the two.”
Somewhat embarrassed to have remembered the opposite given that I read this just last week. Thanks!
Thanks for your comment! I’m actually attending the Global Tipping Points Conference right now, and the leading scientists still say there are mixed results regarding net temperature change in post-collapse scenarios and that overall change hides what could be very different summers and winter results. It very much depends on how much warming we have already experienced at the time of a potential AMOC collapse, as well as the state of other interconnected regional climate systems—like the ice sheets. Suffice it to say it’s tough to model. I think it’s fair to say, though, that it wouldn’t just “cancel out,” as there are the ITCZ shift, the monsoon changes, Northern Hemisphere drying, and other knock-on effects outside of surface air temperature.