ANY estimation of the timing of a tipping point must take into account the uncertainties, which are so considerable that they are all inadequate in the light of day, when made. Bet you won’t read that in the media?

From The KlimaNachrichten Editor

By Fritz Vahrenholt and Frank Bosse

A reminiscence of an article about the imminent “tipping point” of the Atlantic overturning circulation:

At the end of July 2023, we reported on a paper that thought it had identified the “tipping point” of the Atlantic Overturning Circulation (AMOC): It should (most likely) be ready as early as 2057. It kicked up a lot of dust, we described it. Our summary at the time:

“DD23 is an exercise in statistics, very far from any evidence of physical significance for the AMOC itself. The conclusions are not supported by the content of the paper.”  

In the meantime (mid-September 2023), another, not yet peer-reviewed (preprint) paper appeared, which finds very similar. It uses several data series for sea surface temperatures (SST) and another “fingerprint” of the AMOC, a dipole that avoids the warming itself from being included in the result of the AMOC decrease sought.

And lo and behold: she comes to completely different conclusions. Depending on which series one uses (especially in the early years up to about 1950 they are very incomplete in direct observation and what is missing is supplemented by various “infill methods” that have a strong effect on the statistics on which the article in question is based) one comes to completely divergent results. Thus, the “collapse” of the AMOC is postponed by almost a hundred years, if you use the same “fingerprint”, only a different SST series (instead of HadISST1 ERSSTv5).

The other, also SST-based “fingerprint” postpones the “collapse” determined by the methods of the paper to between 2100 and the year 3300 and beyond! At the end, the authors, including, interestingly, Niklas Boers of PIK, who is probably concerned about the scientific reputation of the institution, write:

“We emphasize that these uncertainties, originating from underlying modelling or mechanistic assumptions as well as from the employed empirical data, need to be taken into account and propagated thoroughly before attempting to estimate a future tipping time of any potential Earth system tipping element.”  

ANY estimation of the timing of a tipping point must take into account the uncertainties, which are so considerable that they are all inadequate in the light of day, when made. Bet you won’t read that in the media? They had their hands full, with the active help of Prof. Rahmstorf, also from PIK, to propagate the imminent end of the AMOC. That’s what the attentive reader has this blog for.