Everyone knows that trees capture CO2 from the air; Nature Communications found that they can cool the planet in another way – by forming low clouds over forests. Most of the clouds are created by evergreen needle forests, Phys reports.
Moreover, when the trees are covered with snow in winter, the clouds over the forests become much less than in the open space. Now you can dislike those who are engaged in illegal logging even more.
Satellites reveal how forests increase cloud and cool climate (image by European Space Agency)
Forests are not the only key to moderating our climate by sequestering atmospheric carbon, but they also create a cooling effect by increasing low-level clouds. A first global assessment using satellite observations has shown that afforestation increases low-level cloud cover for two-thirds of the world, with the outcome being most substantial over evergreen needleleaf forest.
Because trees sequester carbon dioxide from the atmosphere and convert it into biomass, forests are widely championed for their role in mitigating climate change. However, what has been less clear is how forests affect the climate in other ways, such as their role in the water cycle and surface energy balance.
The paper, published recently in Nature Communications, uses global data records of cloud and land-fractional cover produced by ESA’s Climate Change Initiative to examine the effect of the transition of vegetation cover into the lightning strikes that cause some wildfiresdeciduous and evergreen forest.
“Earth observations are increasingly showing that trees and forests are impacting climate by affecting biophysical surface properties,” says one of the co-authors of the study, Alessandro Cescatti.
The paper describes how cloud generally increased over the whole year in afforested areas in temperate, tropical, and arid regions, sometimes by as much as 15%.
However, during the boreal winter and spring across North America, Russia, and Eastern Europe, when these regions have prolonged snow cover, the authors found a reduction in cloud cover over forests compared to open land. On the other hand, the boreal summer has solid and consistent increases in cloud fraction by about 5%.
“Without global cloud and land-cover type observations from satellites, this study would not have been possible on a global scale,” says Martin Stengel. He was not involved in the study but leads the Climate Change Initiative Cloud project. “The authors of this study appreciated the high-spatial-resolution of the initiative’s products.”
Dr. Cescatti added, “Studies like this one, based on robust satellite observations, are fundamental to characterize the complexity of the climate system and provide benchmarks for climate model developments.”
The team emphasizes that land-based climate mitigation through afforestation, forest restoration, and avoided deforestation should not be reasoned purely in terms of carbon capture. Instead, policies should include the more comprehensive climate benefits that forests offer, including increasing cloud cover for localized cooling and generating rainfall, giving forests additional hydrological value.
