How to Moderate Climate Change: Plant More Trees to Avoid Warming

First Posted: Apr 29, 2013 10:55 AM EDT

How do we moderate climate change? Plant more trees. A new study reveals that plants can actually release gases that help form clouds and cool the atmosphere. That's sure to provide some incentive for drought-stricken areas.

Researchers have known for quite some time that aerosols, which are particles that float in the atmosphere, tend to cool the climate as they form cloud droplets which reflect sunlight. These aerosols can come from many different sources, including human emissions. However, the effects of a biogenic aerosol, which is particulate matter that originates from plants, aren't as well-studied.

Plants actually release gases that, after atmospheric oxidation, tend to stick to aerosol particles. This causes the original particles to grow and reflect more sunlight. This also serves as the basis for cloud droplets.

In order to understand a bit more about this phenomenon and how it might affect our climate, researchers collected data at 11 different sites from around the world. They measured the concentrations of aerosol particles in the atmosphere, along with the concentrations of plant gases and temperature. They also reanalyzed estimates for the height of the boundary layer, which is the layer of air closest to Earth in which gases and particles mix effectively. This layer actually changes with weather, which made it a key variable in the scientists' estimates.

So what did researchers find? They discovered that as temperatures rise, there's an increase of natural aerosols which have a cooling effect on the atmosphere. In other words, plants actually reacted to changes in temperature and aided in the cooling effect.

That's not going to save us from climate change, though. The effect of enhanced plant gas emissions on climate only countered about one percent of warming.  However, that effect had far more of an impact on the regional scale; it could potentially counter 30 percent of warming in more rural, forested areas where anthropogenic emissions of aerosols were much lower in comparison to the natural aerosols.

While this study may show that trees won't have a major impact on cooling, it does show how they might affect something else. The research could have major implications for climate models.

"Aerosol effects on the climate are one of the main uncertainties in climate models," said lead researcher, Pauli Paasonen, in a press release. "Understanding this mechanism could help us reduce those uncertainties and make the models better."

The findings are published in the journal Nature Geoscience.

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