Abstract
Global mean surface air temperature (T) variability on subdecadal
timescales can be of substantial magnitude relative to the long-term
global warming signal and such variability has been associated with
considerable environmental and societal impacts. Therefore,
probabilistic foreknowledge of short-term T evolution may be of value
for anticipating and mitigating some course-resolution climate-related
risks. Here we present an empirically-based methodology that utilizes
global spatial patterns of annual surface air temperature to predict
subsequent annual T anomalies via Partial Least Squares Regression. The
method’s skill is achieved via information on the state of long-term
global warming as well as the state and recent evolution of the El
Niño-Southern Oscillation and the Interdecadal Pacific Oscillation. We
test the out-of-sample skill of the methodology using a “forecast
mode” where statistical predictions are made precisely as they would
have been if the procedure had been operationalized starting in the year
2000. The forecast errors for lead times of 1 to 4 years are smaller
than naïve benchmarks using persistence and perform favorably relative
to most dynamical Global Climate Models retrospectively initialized to
the observed state of the climate system. Thus, this method can used as
a computationally-efficient benchmark for dynamical model forecast
systems.