Good News on Forests and Carbon Dioxide   
       
   Dec 31, 2014:  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 in the   
   Proceedings of National Academy of Sciences.   
       
   [Photo link missing]   
       
   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   
       
   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."   
       
   Credits:   
   Production editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More information:   
       
   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   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.99   
    * Origin: NCS BBS - Houma, LoUiSiAna (1:3828/7)