Public perceptions of pollen seasons under climate change

Political ideology and scientific communication shape human perceptions of pollen seasons

Allergen phenology
First-author
PNAS Nexus 2026
Master’s student Chuangbo Tong, undergraduate student Luke Hamilton, and undergraduate student Cait Schilt at the University of California, Santa Cruz contributed to the exploratory data analysis of this project.
Authors

Yiluan Song

Adam Millard-Ball

Nathan Fox

Derek Van Berkel

Arun Agrawal

Kai Zhu

Published

December 26, 2025

Keywords

global change biology, environmental data science, allergy, climate change, phenology, public health, social media

Paper GitHub

Highlights

  • Pollen-related Twitter posts correspond to pollen seasons over time and space.
  • Twitter users’ attribution of changes in pollen seasons depend on their ideology.
  • More liberal users are more likely to agree with climate impacts on pollen seasons.
  • Media and experts play key roles in communicating climate impacts on pollen seasons.

Abstract

Climate change is altering the timing and intensity of pollen seasons, increasing human exposure to allergenic pollen. Climate-driven changes in pollen seasons present a unique opportunity to craft messaging that communicates how climate change is affecting biological systems. However, it is unclear how pollen seasons are experienced and understood by the public, including how well we detect pollen seasons and what factors we view as responsible for changes in pollen seasons. Here, we use social media data (Twitter) in the United States from 2012 to 2022 to assess public perceptions of pollen seasons across the country. We find that pollen seasons detected by social media users are consistent with natural pollen seasons. Attribution of changing pollen seasons, however, varies based on political ideology: liberal users are more likely to attribute changing pollen seasons to climate change when compared with conservative users. Mass media and scientific experts shape communication about how climate change drives changes in pollen seasons. Our findings reveal how political ideology and scientific communication affect public perceptions of pollen seasons and climate change. Our findings are a key step towards improved communication of climate change impacts.

Twitter users accurately detect pollen phenology

Twitter pollen phenology aligns with natural pollen phenology over time and space. (a) Twitter pollen phenology aligns with natural pollen phenology over time and space. (b) Both Twitter and natural pollen phenology exhibit latitudinal gradients. (c) Spatial variation of pollen phenology across states in the US.

Attribution to climate change depends on political ideology

Twitter users’ attribution of pollen phenology was likely ideologically structured. (a) Venn diagram showing the relationship between three groups of continental US Twitter users defined for this study. (b) Density and kernel density estimates of ideology score in three groups of users. (c & d) Correlation between the conditional probability of a user attributing changes in pollen phenology to a specific driver (temperature change or climate change) given general interest in pollen phenology and the bin of ideology the user was in.

Scientific communication dominates discussions on climate change impacts

Role of scientific communication on Twitter users’ discussions on pollen phenology. The series of Sankey diagrams show the flow of messages from the source (users being retweeted) to the destination (users posting retweets) in our compiled dataset.