GCM-driven Projections of Future Pollen Emissions and Counts over the United States

Climate change is expected to alter allergenic pollen seasonality for various pollen-emitting taxa. In addition to airborne pollen, particles of respirable size (subpollen particles, SPP) released from pollen rupture may contribute to allergy asthma. Given the prevalence of allergenic disease in the United States, it is crucial to understand how climate change will translate to changes in SPP as well as whole pollen. Moreover, rising global temperatures are expected to shift patterns of atmospheric transport and regional precipitation, which also affect the emissions and distribution of pollen and SPP. We use a comprehensive phenological model - Pollen Emissions for Climate Models version 1 (PECM1.0) - driven with ensemble of global climate model (GCM) temperatures to predict changes to the start and end dates of the pollen season for a variety of allergenic tree taxa, grasses and ragweed over the United States. We evaluate the phenological changes in emissions for two different future greenhouse gas emissions scenarios (RCP4.5 and RCP8.5). Next, we conduct regionally-downscaled simulations of pollen emissions, rupture and release of SPP, and transport to project future pollen and SPP concentrations under climate change. Specifically, we attribute changes in pollen and SPP counts to global temperature effects on pollen phenology and meteorological impacts on pollen and SPP emissions and fate.