Terpenes in Cloud Seeding
Trees use terpenes for their advantage in fascinating ways. When the conifers have not received enough water, and when the conditions are right, they emit terpenes to manipulate their environment and bring themselves rain. Clouds, composed of water vapor, condense around aerosols, and researchers have found that ozone located in the upper atmosphere sticks to molecules of alpha-pinene, a terpene released by pine trees. These highly-ozonated molecules stick together to form heavier particles and serve as an aerosol base for clouds to form to block sunlight and produce rain.6 While humanity has been trying to control and modify the climate for as long as we’ve existed through ceremonial dances, pre-historic sacrifices, and decades of research, trees have been doing so all along.
The most recent CLOUD experiment, a collaboration between around 80 scientists at the CERN particle physics lab near Geneva, increased our understanding of what was in the atmosphere before humans began adding pollution - and what it may be like again in the future. Most cloud droplets need tiny airborne particles to act as ‘seeds’ for their formation and growth. Terpenes emitted from these trees are a viable seed upon which a cloud can generate upon. If a cloud has more of these seeds, it will appear brighter and reflect away more sunlight from the Earth’s surface. This in turn cools the Earth and our climate. Therefore, understanding the number and size of terpenes, among other seeds, in the atmosphere is vital to predicting not only how bright and reflective the planet’s clouds are, but what global temperatures will be.
The discovery that organisms use terpenes to influence their world has huge implications regarding the importance of terpenes in the environment and the role they play in controlling weather. Since one of terpene’s functions is to spur cloud formation, this discovery, adds another two layers to the already well-understood problems associated with cutting down vast swaths of forestry in the process of industrialization. Rising temperatures has an immense number of effects and implications, ranging from rising sea levels, increased droughts and heat waves, to intensified tropical storms.
Since isoprene and other terpenes play a significant role in cloud formation, deforestation has an even bigger impact on the environment than previously thought and the production of terpenes may be integral in slowing the rising temperatures leading to climate change. One is obvious: clouds provide shade, reflecting a broad spectrum of sunlight thanks to their white color. The second, less obvious effect is the greenhouse action of H2O. If a reduction in atmospheric terpenes caused by deforestation does significantly inhibit cloud formation, water vapor that would otherwise form shady clouds instead remains as heat-trapping ambient humidity—unable to condense in the absence of aerosols. Without an abundance of terpene-emitting trees and plants in our environment, a slew of environmental and ecological issues arises.