Warming will result in an earlier start of the pollen season and extending it, but this differs across regions, species, traits and flowering periods . For instance, in different parts of WCE and NEU, the start of birch-season flowering has been shifted and extended up to 2 weeks earlier during recent decades . Airborne pollen concentrations are projected to increase across Europe . In south-eastern Europe, where pollen already has a substantive impact, the pollen count could increase more than 3 to 3.5 times at 2.5°C GWL and can become a more widespread health problem across Europe, particularly where it is currently uncommon  .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report