  The rotational evolution of cool stars is governed by magnetised stellar
winds which slow the stellar rotation during their main sequence lifetimes.
Magnetic variability is commonly observed in Sun-like stars, and the changing
strength and topology of the global field is expected to affect the torque
exerted by the stellar wind. We present three different methods for computing
the angular momentum loss in the solar wind. Two are based on MHD simulations
from Finley & Matt (2018), with one using the open flux measured in the solar
wind, and the other using remotely-observed surface magnetograms. Both methods
agree in the variation of the solar torque seen through the solar cycle and
show a 30-40% decrease from cycle 23 to 24. The two methods calculate different
average values, $2.9\times10^{30}$erg (open flux) and $0.35\times10^{30}$erg
(surface field). This discrepancy results from the already well-known
difficulty with reconciling the magnetograms with observed open flux, which is
currently not understood, leading to an inability to discriminate between these
two calculated torques. The third method is based on the observed spin-rates of
Sun-like stars, which decrease with age, directly probing the average angular
momentum loss. This method gives $6.2\times10^{30}$erg for the solar torque,
larger than the other methods. This may be indicative of further variability in
the solar torque on timescales much longer than the magnetic cycle. We discuss
the implications for applying the formula to other Sun-like stars, where only
surface field measurements are available, and where the magnetic variations are
ill-constrained.
