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dataset : NOAA-ESRL Trends in Atmospheric Methane, Globally averaged marine surface monthly mean data
NOAA-ESRL Trends in Atmospheric Methane, Globally averaged marine surface monthly mean data
Uncertainties in the global monthly 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 monthly 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 is reported in units of dry-air mole fraction, nanomol/mol, abbreviated, ppb. 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.aftp.cmdl.noaa.gov
When citing this dataset please refer to Ed Dlugokencky, NOAA/ESRL (www.esrl.noaa.gov/gmd/ccgg/trends_ch4/).
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