You need to understand the droplets that make up clouds to understand cloud formation, and you need to understand cloud formation for accurate climate modelling. There are many particles in the atmosphere, including dust, sea salt from the ocean, microorganisms, soot, sulphur, and organic material that can be both viscous and oily. When water vapour is attracted to these particles floating in the atmosphere, droplets form, and scientists have long believed that the viscous and oily organic material produced by pollution could form droplets more slowly than other particles, significantly impacting the formation of clouds.
However, researchers at the Georgia Institute of Technology have found that organic coatings on particles don’t seem to significantly affect the rate at which droplets form. They took both aerial and ground-based measurements of droplet formation from ten different areas of the northern hemisphere, studying a wide range of particles, including some the infamous organic, hydrocarbon-rich particles from the Deepwater Horizon oil spill in the Gulf of Mexico in 2010.
According to Athanasios Nenes, a professor in the School of Earth and Atmospheric Sciences and the School of Chemical and Biomolecular Engineering, ‘It turns out that it doesn’t matter how much goop you have — or don’t have — the droplets take the same time to form. Even in extreme environments like Deepwater Horizon, the rate of droplet formation on particles found over the spill doesn’t differ from that of typical sea salt particles.’
He explained, ‘The reason we care about droplet formation rates is because the more slowly the droplets form, the more droplets you end up having in clouds. This, in turn, affects cloud properties and their climate impacts.’ He concluded by saying that, thanks to their findings, ‘With careful measurements and global deployment of measuring instruments, you can actually resolve outstanding questions in cloud physics and help simplify the descriptions of clouds in climate models.’