The eponym “Walker Circulation” refers to a concept
used by atmospheric scientists and oceanographers in providing a physical
explanation for the El Niño–Southern Oscillation phenomenon,
whereas the eponym “Yule–Walker equations” refers to
properties satisfied by the autocorrelations of an autoregressive process. But
how many statisticians (or, for that matter, atmospheric scientists) are aware
that the “Walker” in both terms refers to the same individual,
Sir Gilbert Thomas Walker, and that these two appellations arose in conjunction
with the same research on the statistical prediction of climate? Like George
Udny Yule (the “Yule” in Yule– Walker), Walker’s
motivation was to devise a statistical model that exhibited quasiperiodic
behavior. The original assessments of Walker’s work, both in the
meteorology and in statistics, were somewhat negative. With hindsight, it is
argued that his research should be viewed as quite successful.