Climate Change Impact on Grass Pollens in SW Ontario “Undetectable”

Abstract

Scientists in the USA and Europe have found significant shifts in the pollen season of trees, grasses and weeds, including earlier start dates, longer seasons, higher peak concentrations and greater pollen production associated with climate change (Zhang et al, 2014 Grass pollen counts for SW Ontario covering the past 20 years since 1998 were analyzed. We identified the start and end dates of each year’s season, the length of the season, total annual counts per year, and the peak levels. Our data show that the start of the pollen season may be delayed marginally, but the data are too variable and unconvincing. We found no increase in the length of the season; if anything the duration of successive grass pollen seasons has slightly diminished. We found virtually no increase in the total yearly grass pollen production or in the peak concentrations in SW Ontario over the past 20 years. Published studies have stated that the pollen season in nearby areas of the USA appears to last longer than in the 1990's and as a result of longer growing seasons the levels of pollen have also increased. This is part of an upward latitudinal shift. Our data reveal an entirely different story. We have found no perceptible change in grass pollen, no increase in total yearly counts, if anything a slightly delayed start to the season resulting in a shorter season. Climatic conditions in neighboring regions around the Great Lakes may be considerably variable and less predictable.