What was done
The authors derived and analyzed long-term (1901-2002) temporal trends in the agroclimate of Alberta, Canada.

What was learned
Shen et al. report that "an earlier last spring frost, a later first fall frost, and a longer frost-free period are obvious all over the province."  They also found that May-August precipitation in Alberta increased 14% from 1901 to 2002, and that annual precipitation exhibited a similar increasing trend, with most of the increase coming in the form of low-intensity events.  In addition, the researchers note that "the area with sufficient corn heat units for corn production, calculated according to the 1973-2002 normal, has extended to the north by about 200-300 km, when compared with the 1913-32 normal, and by about 50-100 km, when compared with the 1943-72 normal."

What it means
Shen et al. conclude that "the changes of the agroclimatic parameters imply that Alberta agriculture has benefited from the last century's climate change," emphasizing that "the potential exists to grow crops and raise livestock in more regions of Alberta than was possible in the past."  They also note that the increase in the length of the frost-free period "can greatly reduce the frost risks to crops and bring economic benefits to Alberta agricultural producers," and that the northward extension of the corn heat unit boundary that is sufficient for corn production "implies that Alberta farmers now have a larger variety of crops to choose from than were available previously."  Hence, they say "there is no hesitation for us to conclude that the warming climate and increased precipitation benefit agriculture in Alberta."