Grains of pollen may be seeding clouds and affecting the planet’s climate in unexpected ways, University of Michigan researchers
write in the journal Geophysical Research Letters. Scientists had assumed that pollen particles were too large to remain in the atmosphere long enough to interact with the sun’s radiation or trigger cloud formation. The study found, however, that pollen grains are capable of disintegrating into much smaller particles and that exposure to humidity can accelerate pollen’s breakdown. Using a cloud-making laboratory chamber, the researchers showed that six common types of pollen — ragweed and oak, pecan, birch, cedar, and pine trees — could break into particles small enough to draw moisture and form clouds. “What happens in clouds is one of the big uncertainties in climate models right now,” author Allison Steiner said.