The lack of rainfall in the Great Lakes region in 2022 created a challenging growing season, but long-term trends show an increase in annual precipitation over the past 50 years, a climatology professor from Michigan State University shared at a recent conference in Ridgetown.
Jeff Andresen, the state climatologist for Michigan, gave a presentation called Wild Weather at the Ontario Agricultural Conference at the Ridgetown Campus of the University of Guelph.
Using data from London, he showed there were 591.2 millimeters of precipitation observed last year, while the normal average is 851.9 mm.
“You’ve got a departure or a deficit here of 260 mm,” Andresen said. “That’s something we don’t see that often. That’s a pretty large departure, and it took place over a long period of time.”
The dry weather began early in the growing season in the spring in Southwestern Ontario. By the summer, there were “widespread drier-than-normal conditions over much of the Great Lakes basin itself, but especially continuing here in southern Ontario,” he said.
Andresen noted the federal government’s Canadian Drought Monitor identified large areas of Ontario as having “abnormally dry conditions.” The Kitchener-Waterloo area was under “extreme drought conditions.”
“As the drought monitor here is defined, that’s a drought you would only expect to see once on average about every 20 years, so fairly unusual conditions at that point in time,” he said in early January. “Still, the long-term dryness persists. You just don’t see it now because of the time of the year and it being in the off-season.”
The dry weather came with “very, very low plant-available moisture” in the top meter of soil, he said.
Along with the lack of rainfall, the 2022 growing season in the region was one to two degrees Celsius warmer than normal, depending on the location, Andresen said.
“You can see a lot of the winter last year, especially the latter half of the winter, we had below normal temperatures, but after that, again, the majority of the days were above the long-term normals,” he said.
“We did have a couple periods here in the fall, notably, where we had extended periods of much warmer than normal, and also some reverse – cooler than normal. Of course, in terms of grain drying down, that’s a major, major factor for that time of the year.”
In terms of the Great Lakes region’s climate, it has become warmer and wetter over time, based on data collected for Michigan since 1895, Andresen said.
Over the past 50 years, there has been an additional 10 to 15 per cent of precipitation annually on average, which is occurring in all months, though in some more than others, he said.
“In Michigan, we’re getting 75 to 100 mm of additional precipitation on average that we didn’t have 50 years ago,” he said. “That’s a whole month’s worth of haste.”
Calling it the most important trend, Andresen said the additional rainfall helps with productivity for plant-based agriculture.
“If you have, on average, a whole additional month of precipitation, you’re going to less likely to run out when it matters, which is typically mid-summer to late-summer,” he said.
The additional precipitation is due to both more precipitation per event and more wet days, he said.
The temperature data Andresen presented for Michigan showed a flatline for the first few decades of the 20th century, followed by a warming period in the 1930s and then a “minor cooling trend” of about 0.25 C in the 1950s through the 1970s.
“That’s been followed by about a 1 C warming since 1980 or so,” he said. “Overall, we’re about 1 C warmer than where we were a century ago, but a lot of the warming has occurred here in the last few decades.”
The warming is occurring in all seasons, Andresen said, but the majority has happened in the winter. As well, nighttime temperatures are rising more rapidly than daytime temperatures, meaning the gap between high and low temperatures is shrinking.
Andresen has also looked at the last freezing temperatures of the spring season and the first freezing temperatures of the fall with data going back to 1981 for Lansing, Mich.
“The last freeze of the spring is now a full week earlier than what it was just a few decades ago. The first freezing temperatures of the fall are at least a week, if not a week and a half, later,” he said. “What we have in the middle here … is a longer frost-free growing season of at least two weeks.”
He said he has had his team look at 55 locations in and around Michigan, and 52 of them showed a similar pattern. Some areas had almost three additional weeks for the growing season.
When he started his position at the university 30 years ago, it was a lot more difficult to determine changes in precipitation or temperature over time, Andresen said.
“Coming up with well-defined trends was not an easy thing to do,” he said. “That is no longer the case. We’re definitely seeing some directions.”