Influence of ENSO, droughts, and temperature rise on pollen and pollen seasons in Australia

The concentration of pollen in the atmosphere is shaped by complex interactions between meteorology, climate, land use and human activities. Understanding these factors is crucial for allergy and asthma sufferers to better manage their conditions. This study examines the influence of weather and climate variables on pollen concentrations and pollen seasons in three Australian cities, using over 13, 16 and 32 years of long-term pollen data. El Niño Southern Oscillation (ENSO), drought, rainfall and vegetation index are among the major variables considered in the study. Grass pollen concentration (seasonal average) increased in Canberra (∼200 % per decade) and Sydney (∼34 % per decade) and likely decreased in Melbourne (∼13 % per decade). Melbourne showed an earlier onset and longer duration of the core grass pollen season. Long-term maximum temperature increased in Melbourne and Sydney while decreased in Canberra during the study years. Long-term daily pollen concentrations depicted a decreasing trend in Melbourne (p < 0.01) and increasing in Sydney (p < 0.01) and Canberra (p < 0.01). Daily maximum temperature had positive associations with daily pollen concentrations, while daily rainfall and humidity were negatively associated. Interannual variability in grass and other pollen concentrations was influenced by large-scale climate phenomena (ENSO cycle, Indian Ocean Dipole). Differential impacts were seen among grass and other pollen during drought and non-drought years in Melbourne. Spring rainfall (r = 0.5-0.7) and EVI (r = 0.3-0.9) had positive correlations with seasonal grass pollen. The findings from this study provide valuable insights for healthcare, scientific community and urban planning activities, especially in managing the health risks posed by allergenic pollen in a changing climate.