05 May 2015:
Pollen May Play Surprising
Role in Climate and Cloud Formation
Grains of pollen can break into even smaller particles.
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 — something that allergy researchers have known for quite some time — 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 pull in moisture and form clouds. "What happens in clouds is one of the big uncertainties in climate models right now," lead researcher Allison L. Steiner said. "One of the things we're trying to understand is how do natural aerosols influence cloud cover and precipitation under present day and future climate."
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