  There is increasing concern that the Atlantic Meridional Overturning
Circulation (AMOC) may collapse this century with a disrupting societal impact
on large parts of the world. Preliminary estimates of the probability of such
an AMOC collapse have so far been based on conceptual models and statistical
analyses of proxy data. Here, we provide observationally based estimates of
such probabilities from reanalysis data. We first identify optimal observation
regions of an AMOC collapse from a recent global climate model simulation.
Salinity data near the southern boundary of the Atlantic turn out to be optimal
to provide estimates of the time of the AMOC collapse in this model. Based on
the reanalysis products, we next determine probability density functions of the
AMOC collapse time. The collapse time is estimated between 2037-2064 (10-90%
CI) with a mean of 2050 and the probability of an AMOC collapse before the year
2050 is estimated to be 59 +/- 17%.
