In this week’s edition of The Big Weather Picture, meteorologist Bob "Tornado Bob" Conzemius joined Heidi Holtan and John Latimer to discuss historical trends in Canadian wildfires, Minnesota air quality and climate change.
Taken together, these metrics show a variable picture: air quality has mostly improved in the last 20 years, while wildfire severity lacks a clear trend but varies considerably year-to-year. Rainfall has increased over the last 100 years, as have daily low temperatures.
Air quality trends
Overall, air quality in Minnesota has improved over the last two decades. However, wind-blown smoke from wildfires can have a marked impact on pollution levels and carries with it significant health impacts.
“It’s sort of an insidious threat because you don’t really notice it until you’re outside, maybe working hard,” Latimer said. “ ... You don’t realize that the air you’re taking in is not good for you. You just kind of find yourself a little short of breath or maybe with a little cough.”
People partaking in strenuous physical activity or with lung or heart issues may feel more severe effects, however. Wildfire smoke carries small particles (labeled PM2.5 by health agencies) which can enter the lungs and, subsequently, the bloodstream. According to the Minnesota Department of Health, particle pollution is linked to lung and heart diseases including heart attacks, bronchitis and asthma.
The Minnesota Pollution Control Agency issues air quality alerts as needed, stressing the link of air quality and health. Sensitive groups include people with breathing conditions like chronic obstructive pulmonary disease, heart disease, high blood pressure as well as pregnant people, children and older adults. In addition, people with increased exposure like workers who have vigorous activities outside, people without air conditioning and people without permanent shelter may experience health effects of poor air quality.
A Minnesota Department of Health study found in 2013, “Between 5 and 10 percent of all residents who died, and 1 to 5 percent of all residents who visited the hospital or emergency room for heart and lung problems, did so partly because of fine particles in the air or ground-level ozone.”
Fire trends
Pervasive smoky air in Minnesota summers tends to originate from wildfires in Canada, brought south by northern winds. Since fires tend to start in wilderness areas without much infrastructure or access, it is difficult for firefighters to contain or put out wildfires.
“It’s not really very easy to get in there and put in a lot of firefighting resources, at least ground-based resources,” Conzemius said. “You can do it by air a bit, but still, getting a lot of resources to those fires is pretty difficult.”
Significant rainfall can put out fires naturally, but lightning from thunderstorms often ignites new fires. Thus, both natural and artificial extinguishing processes struggle to contain these large wilderness fires.
When Conzemius looked at how many acres are burned by wildfires each year in Canada, he didn’t find a significant upward trend. Instead, he observed high variability, with some years having only marginal fires and others burning huge swathes of land.
Part of what distinguishes good years from bad is when the fires start: a fire starting early in the season tends to burn many more acres compared to a fire starting late. Climate change may play a role. As snow and ice melt earlier, the vegetation feeding wildfires emerges earlier and extends the wildfire season. In addition, plants are growing farther north than in pre-industrial times, extending the areas where wildfires can burn.
Conzemius suspects a more distinctive trend may emerge over the next decade. The lack of satellite and other long-range methods to detect and quantify wildfire effects make earlier data less robust, and less easy to compare to current data.
Rainfall and temperature trends
Conzemius also looked at historical precipitation trends.
“If you did a 100-year trend, you’d find an increase in rainfall from our Grand Rapids station going from about 3 inches in the late 1910s to nowadays over 4 inches.”
So, while 2022 and 2023 have been dry years, the overall trend has been toward more precipitation. This tendency holds true for precipitation during the summer season: overall, Minnesota is getting more rain in the summer than it did 100 years ago.
Temperatures also show an upward trend, with daily lows in June increasing by four degrees. Higher temperatures are correlated with more severe wildfires.
Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR).
