The World Allergy Organization (2015) and various scientists have forecast prolonged and more intense pollen seasons resulting from climate change and this has been corroborated using data from NAB stations in northern latitudes of the USA (Ziska et al, 2011). Our NAB station is in SW Ontario, Canada along the northern US border, east of those stations.
Ragweed counts for SW Ontario over the past 18 years since 1998 were analyzed. For each ragweed season, we identified the start and end dates using three different criteria, season duration (# days), total counts, days with “0” counts, & the number of days with high counts.
Our data show that the start of the ragweed season is delayed. Meanwhile, the duration of successive ragweed seasons has become shorter. This has been accompanied by a notable decline in the total seasonal pollen counts for SW Ontario over the past eighteen years.
There are visible signs in the scientific data and literature that climate change is affecting pollen production. Instead of longer, more intense pollen seasons starting earlier, we have shown a local decline in ragweed counts, and a delayed start to a shorter season. The affects of climate change on pollen may be more complicated and less predictable than current science would have us believe. Alternatively, there may be another explanation for the anomoly, but we are unaware of what this is.