CERN study finds plankton produce far more cloud seeds than models predicted

For nearly 50 years, scientists have suspected that microscopic marine plankton play a role in cloud formation over Earth's oceans. Now, a new experiment has confirmed their influence is far greater than anyone anticipated — potentially reshaping how climate models predict future warming.

A Missing Piece in Climate Models

In a paper published this week in the journal Nature, the CLOUD Collaboration at CERN reported that methanesulfonic acid (MSA), a compound derived from gases emitted by marine phytoplankton, can trigger the formation and growth of aerosol particles over cold ocean regions. The study found that particle nucleation rates could be accelerated up to tenfold compared with sulfuric acid and ammonia alone.home+2

The research, led by the University of Helsinki, was conducted in the CERN CLOUD chamber under controlled conditions replicating the ultra-low concentrations and cold temperatures of remote marine air, ranging from +9°C down to −52°C. When temperatures fell below −10°C with even trace ammonia present, MSA formed new particle nuclei just as effectively as sulfuric acid — long considered the primary driver of atmospheric aerosol formation.helsinki+1

"Since MSA and SA generally coexist at similar concentrations in cool marine regions, our findings indicate that particle nucleation rates might be accelerated up to tenfold and growth rates up to twofold compared with sulphuric acid and ammonia alone," said Jasper Kirkby, spokesperson of the CLOUD Collaboration.home

How Plankton Shape Clouds

Marine plankton release dimethylsulfide (DMS) during photosynthesis — the gas responsible for the characteristic smell of the sea. When oxidized in the atmosphere, DMS forms acidic vapors including both sulfuric acid and MSA at comparable concentrations. The CLOUD experiment demonstrated that MSA and sulfuric acid reinforce one another by forming shared molecular clusters, helping fragile nanometer-sized particles survive long enough to grow into cloud condensation nuclei.psi+2

The findings help explain the surprisingly high number of particles observed over the Southern Ocean and in the cold marine upper troposphere — areas where current climate models underestimate cloud condensation nuclei concentrations by more than half.helsinki+1

Implications for Future Climate

The discovery carries particular weight as fossil fuel emissions of sulfur dioxide continue to decline due to pollution controls. With anthropogenic aerosols falling, natural biological sources of cloud seeds from marine plankton may play an increasingly important role in the climate system.home+1

"The CLOUD Collaboration has made an important advance in our understanding of climate," said Gautier Hamel de Monchenault, CERN Director for Research and Computing. "It is crucial to deepen our understanding of aerosols: in this case, increased biogenic CCN will affect estimates of the Earth's climate sensitivity as well as projections of climate warming."home