Explaining Pine Tree Scent’s Potential to Slow Climate Change

Scientists have unravelled the mechanism by which the strong scent produced by pine trees turns into aerosols. These aerosol particles have a cooling effect by aiding cloud formation and reflecting sunlight back into space, so could slow climate change.

Current climate change models cannot predict how many of these particles will form, but this new research, published in Nature, has helped to fill a large gap in our understanding. The team of researchers have found an extra step in the process by which the pine smell (made of volatile organic compounds) turns into aerosols. It has long been known that the pine smell reacts with the oxygen in the forest canopy to form the particles. The extra step is the discovery of ultra-low volatility organic vapours in the air that condense (irreversibly) onto any surface or particle they come into contact with, and so bind to the smallest scent particles, helping them grow and become aerosols.

The discovery is important because the vapours emitted by the pine trees make up around half the aerosols in the forest, so knowing how they form can aid predictions about their behaviour and how they will reduce temperatures. This cooling effect will likely increase in the future as well: in a warmer world with rising CO₂ photosynthesis will be faster, leading to more trees and more emission of these vapours. This, in turn, should slow global temperature rises. However, it is not a long-lasting solution: if forests become too stressed from heat or lack of water, they will stop emitting these vapours.

Nevertheless, they could be beneficial in the medium-term, as Dr Mikael Ehn from the University of Helsinki says: “If you go into a pine forest and notice that pine forest smell, that could be the smell that actually limits climate change.”

To find out more, please visit the original publication at: http://www.nature.com/nature/journal/v506/n7489/full/nature13032.html