CH4 abundance (ppb)
--------------------
  year      measured
--------------------
  2000       1773.04
  2001       1771.03
  2002       1772.60
  2003       1776.93
  2004       1776.91
  2005       1773.96
  2006       1774.69
  2007       1781.15
  2008       1786.82
  2009       1793.27
  2010       1798.62
  2011       1803.01
  2012       1808.17
  2013       1813.28
  2014       1822.48
  2015       1834.00
  2016       1843.17
--------------------