Estimation of Global Methane Emissions for 2000-2012 using the CarbonTracker Europe-CH4 Data Assimilation System

Tuesday, 15 December 2015: 15:25
3024 (Moscone West)
Aki Tsuruta1, Tuula Aalto2, Leif Bjarne Backman2, Janne Juhani Hakkarainen3, Ingrid Theodora van der Laan-Luijkx4, Wouter Peters4, Maarten C Krol5, Renato Spahni6 and Sander Houweling7, (1)Finnish Meteorological Institute, Helsinki, Finland, (2)Finnish Meteorological Institute, Greenhouse Gas Group, Helsinki, Finland, (3)Finnish Meteorological Institute, Atmospheric Remote Sensing Group, Helsinki, Finland, (4)Wageningen University, Wageningen, Netherlands, (5)Utrecht University, Utrecht, Netherlands, (6)University of Bern, Bern, Switzerland, (7)Utrecht University, IMAU, Utrecht, 3584, Netherlands
We present global methane emission estimates for 2000-2012 using the CarbonTracker Europe-CH4 data assimilation system. The model optimizes surface emissions from biosphere and anthropogenic sources using the in-situ atmospheric concentration observations from NOAA and other cooperative networks. The CarbonTracker system is based on the ensemble Kalman filter, where the TM5 transport model is used as an observation operator. The estimated average global total emission for 2001-2012 is 519±37 Tg CH4/yr, with an average growth rate of 3.6 Tg CH4/yr. The emission estimate for the first half of the period (2001-2006) is ca. 10 Tg CH4/yr lower than the 12-year average, and the average growth rate was only 1.5 Tg CH4/yr. The emission estimate and its growth rate increased in the second half of the period (2007-2012) by ca. 12 Tg CH4/yr and ca. 80%, respectively. The differences in the average estimates and the growth rates before and after 2006 are mainly due to the growth of anthropogenic emissions in Asia. The results show no significant trend in Europe. Using the optimized emission estimates, atmospheric concentrations were calculated using TM5, and compared with in-situ, aircraft, and space-born observations. The comparisons generally show good agreements between model estimates and observations.