Previous research has led scientists and politicians to believe that regrowing forests on Northern lands that were cleared in order to grow crops would not decrease global warming. But these studies did not consider the importance of the choices made by farmers in the historical past. The work, with colleagues from the Max Planck Institute for Meteorology and the University of Hamburg, will be published August 2 by Geophysical Research Letters.
The Earth has been getting warmer over at least the past several decades, primarily as a result of the emissions of carbon dioxide from the burning of coal, oil, and gas, as well as the clearing of forests.
One strategy for slowing or reversing the increase in atmospheric concentrations of carbon dioxide is to regrow forests on abandoned agricultural land. But the proposal has been difficult to evaluate, because forests can either cool or warm the climate. The cooling effects come from carbon dioxide uptake. When forests grow, they absorb the greenhouse gas carbon dioxide from the atmosphere, and store the carbon in plant biomass and litter in branches, trunks, roots, and soils. This carbon dioxide absorption has a cooling influence on our planet's temperature.
The warming effect comes from the absorption of solar radiation. Forests are often darker than agricultural lands because they absorb more solar radiation. More importantly, forests in the spring often have snow-free and highly absorbing trees, at a time when fields and pastures are still snow-covered and reflective. As a result, forests generally absorb more sunlight than fields or pasture, and this increased absorption of sunlight has a warming influence, with this effect felt most strongly in the snowy areas of the world.
Previous studies that have attempted to understand the balance between cooling and warming from regrowing a forest considered unrealistic and highly idealized scenarios. The study by Pongratz and colleagues for the first time evaluated the climate cooling potential of reforestation taking historical patterns of land-use conversion into consideration.
Pongratz and colleagues found that farmers generally chose to use land that was more productive than average, and therefore richer in carbon. Furthermore, farmers generally chose to use land that was less snowy than average. While this result is not in itself surprising, its implications for the cooling potential of reforestation previously had been ignored. Regrowing forest on these productive lands can take up a lot of the greenhouse gas carbon dioxide, and therefore have a strong cooling influence. Because these lands are not very snowy, regrowing forests would not absorb very much additional sunlight. The net effect of the historical preference for productive snow-free land was to increase the climate cooling potential for reforestation on this land.
"Taking historical factors into account, we believe that we have shown that reforestation has more climate cooling potential than previously recognized," Pongratz said. "We are still not yet at the point where we can say whether any particular proposed reforestation project would have an overall cooling or warming influence. Nevertheless, broad trends are becoming apparent. The cooling effect of reforestation is enhanced because farmers in the past chose to use productive lands that are largely snow free."
The Department of Global Ecology was established in 2002 to help build the scientific foundations for a sustainable future. The department is located on the campus of Stanford University, but is an independent research organization funded by the Carnegie Institution. Its scientists conduct basic research on a wide range of large-scale environmental issues, including climate change, ocean acidification, biological invasions, and changes in biodiversity.
The Carnegie Institution for Science (carnegiescience.edu) is a private, nonprofit organization headquartered in Washington, D.C., with six research departments throughout the U.S. Since its founding in 1902, the Carnegie Institution has been a pioneering force in basic scientific research. Carnegie scientists are leaders in plant biology, developmental biology, astronomy, materials science, global ecology, and Earth and planetary science.
Julia Pongratz | EurekAlert!
Climate change weakens Walker circulation
20.10.2017 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen
Shallow soils promote savannas in South America
20.10.2017 | Senckenberg Forschungsinstitut und Naturmuseen
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research