Smells like tree spirit

Researchers find the missing step to cooling effect in boreal forests

Graphic: Scott Ford

An international team of researchers recently found a missing link in one of the mysteries surrounding climate change. Published in the journal Nature, the study is able to fully explain why chemical compounds such as the sweet-smelling vapours from pine trees are able to buffer some of the effects of global warming in boreal forests.

Prominent forests smells, such as the scent emitted by coniferous trees in the forest, seem like nothing more than a pleasant byproduct of the natural environment. However, this potent scent, which is made up of volatile organic compounds, combines with oxygen particles to form a type of aerosol.

Aerosols are defined as fine particles that can be found within the air. While major sources of aerosols include smoke, dust, and industrial pollutants, aerosols formed by the pine tree scent are able to create a cooling effect for the forest by creating clouds that both scatter the sun’s rays and reflect them back up into space.

Researchers studied the pine scent compound by extracting it from the air in forests in Finland. Finland is the most forest-abundant country in Europe, with 74.2 per cent of its land covered by forests. Its forests are also some of the most extensively studied in Europe. The particles from the Finnish trees were tested in an air chamber located at the Institute for Energy and Climate Research in Jülich, Germany.

Although it was known that the aerosol particles could provide a cooling effect, little was known about the mechanism by which many aerosols actually worked.

Using the advanced technology in the laboratory in Jülich, researchers were able to discover an extra step in the aerosol’s formation. By studying how the oxidation of α-pinene (pine scent) proceeds, the international group of researchers discovered the presence of low-volatility vapours in the air.

These low-volatility vapours are the missing link in the transformation of α-pinene to aerosol compounds. The vapours stick to the small α-pinene particles and help them grow to a size where they can become aerosols.

Although the cooling effect created by these aerosols is an important revelation for its role in climate change, researchers are careful not to overestimate this mechanism as a solution to global warming. In fact, if the forests and the trees become too stressed from global warming, they may not release the vapours at all.