Measurements of atmospheric CH4 from air samples collected weekly at 46 remote surface sites show that, after a decade of near‐zero growth, globally averaged atmospheric methane increased during 2007 and 2008. During 2007, CH4 increased by 8.3 ± 0.6 ppb. CH4 mole fractions averaged over polar northern latitudes and the Southern Hemisphere increased more than other zonally averaged regions. In 2008, globally averaged CH4 increased by 4.4 ± 0.6 ppb; the largest increase was in the tropics, while polar northern latitudes did not increase. Satellite and in situ CO observations suggest only a minor contribution to increased CH4 from biomass burning. The most likely drivers of the CH4 anomalies observed during 2007 and 2008 are anomalously high temperatures in the Arctic and greater than average precipitation in the tropics. Near‐zero CH4 growth in the Arctic during 2008 suggests we have not yet activated strong climate feedbacks from permafrost and CH4 hydrates.

[1] Sixteen mixtures of methane (CH 4 ) in dry air were prepared using a gravimetric technique to define a CH 4 standard gas scale covering the nominal range 300-2600 nmol mol À1 . It is designed to be suitable for measurements of methane in air ranging from those extracted from glacial ice to contemporary background atmospheric conditions. All standards were prepared in passivated, 5.9 L high-pressure aluminum cylinders. Methane dry air mole fractions were determined by gas chromatography with flame ionization detection, where the repeatability of the measurement is typically better than 0.1% ( 1.5 nmol mol À1 ) for ambient CH 4 levels. Once a correction was made for 5 nmol mol À1 CH 4 in the diluent air, the scale was used to verify the linearity of our analytical system over the nominal range 300-2600 nmol mol À1 . The gravimetrically prepared standards were analyzed against CH 4 in air standards that define the Climate Monitoring and Diagnostics Laboratory (CMDL) CMDL83 CH 4 in air scale, showing that CH 4 mole fractions in the new scale are a factor of (1.0124 ± 0.0007) greater than those expressed in the CMDL83 scale. All CMDL measurements of atmospheric CH 4 have been adjusted to this new scale, which has also been accepted as the World Meteorological Organization (WMO) CH 4 standard scale; all laboratories participating in the WMO Global Atmosphere Watch program should report atmospheric CH 4 measurements to the world data center on this scale.