Reforestation could cool the planet more than thought

Madrid, 10 ago. (European Press) –

Reforestation is among the simplest and most attractive natural climate solutions, but the effect of trees on atmospheric temperature It’s more complicated than it seems.

One question scientists are asking is whether reforesting places at mid-latitudes such as North America or Europe could actually warm the planet. Forests absorb large amounts of solar radiation as a result of reduced albedo, which is a measure of a surface’s ability to reflect sunlight.

In the tropics, reduced albedo corresponds to increased uptake of carbon dioxide through dense vegetation throughout the year. But in temperate climates, the concern is that the heat trapped by the sun It can counteract any cooling effects that forests can provide by removing carbon dioxide from the atmosphere.

But a new study by Princeton University researchers finds that these concerns may be missing a crucial ingredient: drag. They report in the Proceedings of the National Academy of Sciences that more intense cloud formations associated with forest areas mean that reforestation is likely to It would be more effective at cooling the Earth’s atmosphere than previously thought.

“The main thing is that no one knew if planting trees in mid-latitudes was good or bad because of the problem of albedo,” he said. It’s a statement Corresponding author Amilcare Porporato, Thomas J. Wu’94 Professor of Civil and Environmental Engineering at Princeton and High Meadows Institute for the Environment (HMEI). “We show that if you consider that clouds tend to form frequently over forest areas, So planting trees in large areas is beneficial and should be done for climatic purposes.”

As anyone who feels a cloud pass over the sun on a hot day knows, Daytime clouds have a cooling, albeit fleeting, effect on Earth. In addition to directly blocking the sun’s rays, the clouds have a high albedo that resembles ice and snow. However, clouds are known to be difficult to study and have been largely excluded from many studies investigating the efficacy of mitigating natural climate change, Including reforestationPurburato said.

To consider reforestation in the context of cloud cover, Porporato worked with lead author Sara Cerasoli, a graduate student at Princeton University in civil and environmental engineering, and Jun Ying, an assistant professor at the University of Information Science and Technology in Nanjing, who was previously a postdoc. . Fellow of the Porporato Research Group. His work has been supported by the HMEI-based Carbon Mitigation Initiative.

Purburato and Yen previously reported that climate models underestimate the cooling effect of the daily cloud cycle. They also mentioned last year that climate change It can lead to an increase in daily cloud cover in arid regions such as the southwestern United States, which is currently considered ideal for solar energy production.

For the latter study, Cerasoli, Porporato, and Yin investigated the effect of vegetation on cloud formation in mid-latitudes by combining satellite cloud cover data from 2001 to 2010 with models related to the interaction between plants and the atmosphere.

The researchers modeled the interactions between different types of vegetation and the atmospheric boundary layer, which is the lowest layer of the atmosphere and interacts directly with the Earth’s surface, to determine whether cloud formation is affected differently by the type of vegetation. They focused on regions in the latitudinal range of 30 to 45 degrees, roughly from the subtropics to the semi-arid regions such as the North Midwest of the United States. They considered the effects of both reforestation (restoration of lost tree cover) and afforestation, Which involves planting forests in previously treeless areas, although this may have other environmental costs.

The team found that for mid-latitudes, the cooling effect of clouds, in addition to sequestering carbon, outweighs the solar radiation absorbed by forest areas.

Models showed that clouds form more often over forest areas than over grasslands and other areas with little vegetation, and that this improved cloud formation had a cooling effect on Earth’s atmosphere. The researchers note from satellite data that clouds also tend to form in the early afternoon over forested areas, This results in a longer duration of cloud cover and a longer time for clouds to reflect solar radiation away from the Earth.

The results can help establish policies for allocating land for reforestation and agriculture; Wetter mid-latitudes such as the eastern United States or southeastern China are suitable for reforestation and afforestation, but are also attractive for cultivation. The study authors report that one approach is to combine mid-latitude reforestation with distribution of drought-tolerant crops in areas less suitable for reforestation.

However, the authors urged caution when making the leap from science to policy. “Not only can we consider climate change, but we must also take into account other factors, such as biodiversity and the fact that land is also essential for food production,” said Serrasoli. “Future studies should continue to look at the role of clouds, but should focus on more specific regions and take their economies into account.”