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NASA Finds Good News on Forests and Carbon Dioxide

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A new NASA study suggests that tropical forests, like this one in Malaysia, absorb more atmospheric carbon dioxide than is absorbed by forests in Alaska, Canada and Siberia. (Image credit: Wikimedia Commons)
A new NASA study suggests that tropical forests, like this one in Malaysia, absorb more atmospheric carbon dioxide than is absorbed by forests in Alaska, Canada and Siberia. (Image credit: Wikimedia Commons)

PRESS RELEASE (NASA/JPL) – A new NASA-led study shows that tropical forests may be absorbing far more carbon dioxide than many scientists thought, in response to rising atmospheric levels of the greenhouse gas. The study estimates that tropical forests absorb 1.4 billion metric tons of carbon dioxide out of a total global absorption of 2.5 billion — more than is absorbed by forests in Canada, Siberia and other northern regions, called boreal forests.

“This is good news, because uptake in boreal forests is already slowing, while tropical forests may continue to take up carbon for many years,” said David Schimel of NASA’s Jet Propulsion Laboratory, Pasadena, California. Schimel is lead author of a paper on the new research, appearing online today in the Proceedings of National Academy of Sciences.

Forests and other land vegetation currently remove up to 30 percent of human carbon dioxide emissions from the atmosphere during photosynthesis. If the rate of absorption were to slow down, the rate of global warming would speed up in return.

The new study is the first to devise a way to make apples-to-apples comparisons of carbon dioxide estimates from many sources at different scales: computer models of ecosystem processes, atmospheric models run backward in time to deduce the sources of today’s concentrations (called inverse models), satellite images, data from experimental forest plots and more. The researchers reconciled all types of analyses and assessed the accuracy of the results based on how well they reproduced independent, ground-based measurements. They obtained their new estimate of the tropical carbon absorption from the models they determined to be the most trusted and verified.

“Until our analysis, no one had successfully completed a global reconciliation of information about carbon dioxide effects from the atmospheric, forestry and modeling communities,” said co-author Joshua Fisher of JPL. “It is incredible that all these different types of independent data sources start to converge on an answer.”

The question of which type of forest is the bigger carbon absorber “is not just an accounting curiosity,” said co-author Britton Stephens of the National Center for Atmospheric Research, Boulder, Colorado. “It has big implications for our understanding of whether global terrestrial ecosystems might continue to offset our carbon dioxide emissions or might begin to exacerbate climate change.”

As human-caused emissions add more carbon dioxide to the atmosphere, forests worldwide are using it to grow faster, reducing the amount that stays airborne. This effect is called carbon fertilization. “All else being equal, the effect is stronger at higher temperatures, meaning it will be higher in the tropics than in the boreal forests,” Schimel said.

But climate change also decreases water availability in some regions and makes Earth warmer, leading to more frequent and larger wildfires. In the tropics, humans compound the problem by burning wood during deforestation. Fires don’t just stop carbon absorption by killing trees, they also spew huge amounts of carbon into the atmosphere as the wood burns.

For about 25 years, most computer climate models have been showing that mid-latitude forests in the Northern Hemisphere absorb more carbon than tropical forests. That result was initially based on the then-current understanding of global air flows and limited data suggesting that deforestation was causing tropical forests to release more carbon dioxide than they were absorbing.

In the mid-2000s, Stephens used measurements of carbon dioxide made from aircraft to show that many climate models were not correctly representing flows of carbon above ground level. Models that matched the aircraft measurements better showed more carbon absorption in the tropical forests. However, there were still not enough global data sets to validate the idea of a large tropical-forest absorption. Schimel said that their new study took advantage of a great deal of work other scientists have done since Stephens’ paper to pull together national and regional data of various kinds into robust, global data sets.

Schimel noted that their paper reconciles results at every scale from the pores of a single leaf, where photosynthesis takes place, to the whole Earth, as air moves carbon dioxide around the globe. “What we’ve had up till this paper was a theory of carbon dioxide fertilization based on phenomena at the microscopic scale and observations at the global scale that appeared to contradict those phenomena. Here, at least, is a hypothesis that provides a consistent explanation that includes both how we know photosynthesis works and what’s happening at the planetary scale.”

NASA monitors Earth’s vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records and computer analysis tools to better see how our planet is changing. The agency shares this unique knowledge with the global community and works with institutions in the United States and around the world that contribute to understanding and protecting our home planet.

For more information about NASA’s Earth science activities in the last year, visit:

http://www.nasa.gov/earthrightnow

Media Contact

Alan Buis
Jet Propulsion Laboratory, Pasadena, California
818-354-0474
Alan.Buis@jpl.nasa.gov

Written by Carol Rasmussen
NASA Earth Science News Team

2014-442

Rosetta comet probe team narrows landing site to five locations

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This annotated image depicts four of the five potential landing sites for the Rosetta mission's Philae lander.
This annotated image depicts four of the five potential landing sites for the Rosetta mission’s Philae lander (Courtesy NASA/JPL-Caltech, Image by ESA/Rosetta/MPS for OSIRIS Team).

The European Space Agency’s Rosetta Comet mission has chosen five likely landing sites for its Philae’s lander on comet 67P/Churyumov-Gerasimenko. The lander is scheduled to descend down to the comet’s nucleus in November.

According to a press release by NASA’s Jet Propulsion Laboratory:

Rosetta is an international mission headed up by the ESA with support from NASA, and will be the first ever attempt to land on a comet.

Rosetta is an international mission headed up by the ESA with support from NASA, including providing instruments.

 The European Space Agency’s Rosetta mission has chosen five candidate landing sites on comet 67P/Churyumov-Gerasimenko for its Philae lander. Philae’s descent to the comet’s nucleus, scheduled for this November, will be the first such landing ever attempted. Rosetta is an international mission spearheaded by the European Space Agency with support and instruments provided by NASA.
Picking the landing site is complex and a balancing the technical issues of the orbiter and lander during the entire phases of separation, descent, landing, and all operations on the surface must be precise.

Due to the distance from Earth and the orbiter and lander creates uncertainties in navigating the orbiter close to the comet, the only way possible to pick a landing site in terms of an ellipse, which will cover up to six-tenths of a square mile (or one square kilometer) where the Philae lander might land.

“This is the first time landing sites on a comet have been considered,” said Stephan Ulamec, Philae Lander Manager at the German Aerospace Center, Cologne, Germany in a press release.

“The candidate sites that we want to follow up for further analysis are thought to be technically feasible on the basis of a preliminary analysis of flight dynamics and other key issues – for example, they all provide at least six hours of daylight per comet rotation and offer some flat terrain. Of course, every site has the potential for unique scientific discoveries.”
 For each possible zone, important questions must be asked:

Will the lander be able to maintain regular communications with Rosetta?

 How common are surface hazards such as large boulders, deep crevasses or steep slopes?

Is there sufficient illumination for scientific operations and enough sunlight to recharge the lander’s batteries beyond its initial 64-hour lifetime without causing overheating?

The team reduced the number of landing sites from 10 to five, and gave them letters that have no special meanings.

 Three of the landing sites (B, I and J) are on the smaller lobe of the comet, where the other two sites (A and C) are located on the larger lobe.

“The process of selecting a landing site is extremely complex and dynamic; as we get closer to the comet, we will see more and more details, which will influence the final decision on where and when we can land,” said Fred Jansen, Rosetta’s mission manager from the European Space Agency’s Science and Technology Centre in Noordwijk, The Netherlands, in the same press release.

 “We had to complete our preliminary analysis on candidate sites very quickly after arriving at the comet, and now we have just a few more weeks to determine the primary site. The clock is ticking and we now have to meet the challenge to pick the best possible landing site.”
This image of comet 67P/Churyumov-Gerasimenko shows the diversity of surface structures on the comet...
This image of comet 67P/Churyumov-Gerasimenko shows the diversity of surface structures on the comet’s nucleus. It was taken by the Rosetta spacecraft’s navigation camera on August 7, 2014. At the time, the spacecraft was 65 miles (104 kilometers) away from the 2.5 mile (4 kilometer) wide nucleus. Courtesy NASA/JPL-Caltech, Image by ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DAS
 The next thing the team must do is to prepare a comprehensive analysis of each of the five landing sites so they can determine the best orbital and operational strategies that could be used so Rosetta can deliver the lander to any one of them.

During the time the team is preparing their analysis, Rosetta will move to 31 miles (50 kilometers) of the comet allowing more detailed study of the five landing sites.

 The Rosetta team will have the complete assessments of all five landing sites completed by September 14, and they will be ranked in order to select a primary landing site, with both a full detailed strategy for landing the orbiter at the primary or selected site, along with a backup contingency.

The ESA Rosetta team plans to land the Philae lander sometime around mid-November when the comet will be about 280 million miles (450 million Kilometers). This means the comet will be three times the distance than the Earth is to the Sun (280 million miles also equals 3 astronomical units, where an astronomical unit is 93 million miles, or the distance between the Sun and the Earth).

At 3 AU, there should be little to no activity on the comet that would jeopardize the landing of the Philae lander on the comet’s surface, and just before the comet becomes active.

Launched in March 2004, Rosetta was reactivated in January 2014 after a record 957 days in hibernation. Composed of an orbiter and lander, Rosetta’s objectives since arriving at comet 67P/Churyumov-Gerasimenko earlier this month are to study the celestial object up close in unprecedented detail, prepare for landing a probe on the comet’s nucleus in November, and track its changes through 2015, as it sweeps past the sun.

Illustration of comet-seeker Rosetta with details of its progress
Illustration of comet-seeker Rosetta with details of its progress (AFP/File – P. Pizarro/A. Bommenel/K. Tian)
 Rosetta’s objectives as the spacecraft reached comet 67P/Churyumov-Gerasimenko earlier this month is to do a close up study of the comet in unprecedented detail and to prepare for landing the probe on the comet’s nucleus and track any changes through 2015 as it orbits comet 67P/Churyumov-Gerasimenko.

Cosmologists consider comets as time capsules containing materials left over from building of the Solar System 3.4 billion years ago. Rosetta’s lander will obtain the very first images taken from a comet’s primordial composition by drilling into the surface.

 Scientists will also be able to study how a comet changes its composition as it makes its way around the Sun. It is believed this will help scientists to understand more about the role of comets may have played in seeding the Earth with water, and even life. They will also be able to learn more about the evolution of our Solar System.

According to the press release:

 The scientific imaging system, OSIRIS, was built by a consortium led by the Max Planck Institute for Solar System Research (Germany) in collaboration with Center of Studies and Activities for Space, University of Padua (Italy), the Astrophysical Laboratory of Marseille (France), the Institute of Astrophysics of Andalusia, CSIC (Spain), the Scientific Support Office of the European Space Agency (Netherlands), the National Institute for Aerospace Technology (Spain), the Technical University of Madrid (Spain), the Department of Physics and Astronomy of Uppsala University (Sweden) and the Institute of Computer and Network Engineering of the TU Braunschweig (Germany). OSIRIS was financially supported by the national funding agencies of Germany (DLR), France (CNES), Italy (ASI), Spain, and Sweden and the ESA Technical Directorate.

Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta’s Philae lander is provided by a consortium led by the German Aerospace Center, Cologne; Max Planck Institute for Solar System Research, Gottingen; French National Space Agency, Paris; and the Italian Space Agency, Rome. NASA’s Jet Propulsion Laboratory in Pasadena, California, a division of the California Institute of Technology, manages the U.S. participation in the Rosetta mission for NASA’s Science Mission Directorate in Washington.

For Specifications on: 67P/Churyumov-Gerasimenko