# -------------------------------------------------------------------- # USE OF NOAA GML DATA # # These data are made freely available to the public and the # scientific community in the belief that their wide dissemination # will lead to greater understanding and new scientific insights. # The availability of these data does not constitute publication # of the data. NOAA relies on the ethics and integrity of the user to # ensure that GML receives fair credit for their work. If the data # are obtained for potential use in a publication or presentation, # GML should be informed at the outset of the nature of this work. # If the GML data are essential to the work, or if an important # result or conclusion depends on the GML data, co-authorship # may be appropriate. This should be discussed at an early stage in # the work. Manuscripts using the GML data should be sent to GML # for review before they are submitted for publication so we can # ensure that the quality and limitations of the data are accurately # represented. # # Contact: Ed Dlugokencky (303 497 6228; ed.dlugokencky@noaa.gov) # # File Creation: Fri Nov 5 04:05:03 2021 # # RECIPROCITY # # Use of these data implies an agreement to reciprocate. # Laboratories making similar measurements agree to make their # own data available to the general public and to the scientific # community in an equally complete and easily accessible form. # Modelers are encouraged to make available to the community, # upon request, their own tools used in the interpretation # of the GML data, namely well documented model code, transport # fields, and additional information necessary for other # scientists to repeat the work and to run modified versions. # Model availability includes collaborative support for new # users of the models. # -------------------------------------------------------------------- # # # See www.esrl.noaa.gov/gmd/ccgg/trends_ch4/ for additional details. # # Uncertainties in the global annual means are estimated using two # terms: The first is a bootstrap (resampling) method that varies the # sites in our network. Each pseudo-network contains the same number of # sites as our actual NOAA ESRL cooperative global air sampling network, # but some are repeated and some are excluded. The second term is a # Monte Carlo method that randomly modifies the data to account for # measurement uncertainty. In both cases, 100 globally-averaged time # series are created. Standard deviations of the annual means are # calculated, and the two terms (network and analytical) are taken in # quadrature to give the reported uncertainties. Please see Dlugokencky # et al., 1994, JGR, vol. 99, 17021-17043, for a complete discussion. # # CH4 expressed as a mole fraction in dry air, nanomol/mol, abbreviated as ppb # # NOTE: In general, the data presented for the last year are subject to change, # depending on recalibration of the reference gas mixtures used, and other quality # control procedures. Occasionally, earlier years may also change for the same # reasons. Usually these changes are minor. # # year mean unc 1984 1644.68 0.67 1985 1657.28 0.51 1986 1670.08 0.79 1987 1682.72 0.51 1988 1693.19 0.55 1989 1704.54 0.52 1990 1714.42 0.68 1991 1724.84 0.65 1992 1735.51 0.61 1993 1736.50 0.47 1994 1742.06 0.62 1995 1748.80 0.54 1996 1751.46 0.64 1997 1754.54 0.42 1998 1765.54 0.67 1999 1772.39 0.58 2000 1773.39 0.77 2001 1771.24 0.55 2002 1772.69 0.52 2003 1777.38 0.53 2004 1777.03 0.54 2005 1774.15 0.58 2006 1774.97 0.55 2007 1781.44 0.59 2008 1787.00 0.57 2009 1793.55 0.69 2010 1798.95 0.66 2011 1803.11 0.66 2012 1808.03 0.58 2013 1813.39 0.68 2014 1822.61 0.46 2015 1834.25 0.52 2016 1843.15 0.61 2017 1849.67 0.69 2018 1857.31 0.81 2019 1866.60 0.56 2020 1879.11 0.63