WINTER PRECIPITATION
As reported previously in the publication " Indicators of Climate Change
for British Columbia" , quite large areas of the province have shown a
steady increase in precipitation at the rate of 2-4% per decade. Graphs #
6-8 illustrate that during the non growing season there has been a trend to
wetter conditions, at least at the two long-term climate stations (Agassiz
and Vernon). During the Pacific Decadal Oscillation, south Coast
precipitation during the winter months is somewhat greater under the
influence of the cold or ridge phase. Interestingly, the southern interior
does not show wetter conditions in this same phase. The upper air
circulation that favours a wetter situation on the coast may not extend
into the southern interior. Perhaps this is a function of the Coast
Mountains greater rain shadow effect during the cold or ridge phase.

During the growing season within the last seventy to eighty years, there
has been a steady trend to wetter conditions, both on the south coast and
in the southern interior (graph #9). However, the early record at the south
coastal station at Agassiz does reveal that the earliest part of the record
shows that the wettest years overall were in the late 19th and early part
of the 20th century. It is possible that we are merely returning to what
can be expected from time to time as a part of natural variability.
Therefore, global warming may or may not be responsible for the recent
observed wetter growing seasons.