  The recent addition of orbit-spin coupling torques to atmospheric global
circulation models has enabled successful years-in-advance forecasts of global
and regional-scale dust storms on Mars. Here we explore the applicability of
the orbit-spin coupling mechanism for understanding and forecasting anomalous
weather and climate events on Earth. We calculate the time history of
orbit-spin coupling torques on the Earth system for the interval from
1860-2040. The torque exhibits substantial variability on decadal to bidecadal
timescales. Deep minima recur at intervals from 15-26 years; eight such
episodes are documented within the study period prior to 2020. Each of the
identified torque minima corresponds in time to an episode of widespread
drought in the Western USA extending over several years. The multiyear droughts
of the 1930s, the 1950s, the mid-1970s, the early 1990s, and of 2011-2015 were
each coincident in time with orbit-spin coupling torque minima. The upcoming
torque minimum of 2030 is the deepest such minimum of the 180-yr study
interval. A multiyear episode of widespread drought in the Western USA is
likely to be underway by 2028 plus or minus 4 years (2 standard deviations).
The potential benefits to societies of improved drought predictions justify an
immediate high-priority effort to include forcing by orbit-spin coupling within
state-of-the-art Earth system GCMs. Future targeted numerical modeling
investigations are likely to yield forecasts with considerably lower
uncertainties and with much improved temporal resolution in comparison to that
obtained here.
