  The results of a recent simulation with a complex global climate model
suggest that the overturning component of the freshwater transport at the
southern boundary of the Atlantic could be used as an early-warning indicator
of an AMOC collapse. However, there are two shortcomings. Firstly, the
simulation is based on some implausible assumptions. It is therefore not clear
whether this new indicator will still be helpful in a more realistic setting.
Secondly, the statistical methods employed in the simulation work only for time
series that are much longer than the currently available historical series. As
not much can be done in the short term about the first issue, this paper
focuses on the second issue. It is shown that it is possible to use alternative
statistical methods that can do the job at least as well and, moreover, are
also suitable for short series. Applying these more appropriate methods to
historical data obtained with an ocean reanalysis system, no indication of an
imminent AMOC collapse is found.
