To see precise methane values, hover your mouse cursor over the blue graph trace. (However, all values are shown with at least one more significant digit than is warranted by the precision of the measurements, and the ice core values are less accurate than the Mauna Loa measurements.)
1840-1992 data (in light blue) is from http://cdiac.ornl.gov/ftp/trends/atm_meth/EthCH498B.txt (ice cores), interpolated.
1984-present data (in dark blue) is from ftp://aftp.cmdl.noaa.gov/products/trends/ch4/ch4_annmean_gl.txt (measurements at Mauna Loa Observatory, HI).
The figures are annual averages.
We also have a similar graph for carbon dioxide (CO2), and a combined graph with both CO2 and CH4.