Not sure, but if you get please share with us.

Yes, please have a look at the analysis of the trend in methane concentrations contained in the latest report by the IPCC at page 6-4 (http://www.climatechange2013.org/images/uploads/WGIAR5_WGI-12Doc2b_FinalDraft_Chapter06.pdf)

Thanks Domenico it is interesting link that you sent. These are estimates and not the measured time trends. IPCC reports are anyway assimilation of data points both spatially and temporally seperated.

Domenico this is written on this report IPCC draft report not to cite and distribute. Are you an author and can we use it?

Deniz, Saif: other then the AR5 link posted by Domenico, you can find CH4 data in previous IPCC reports (www.ipcc.ch)

You may also be interested in this nearly classic paper summarizing Vostok ice core data for almost half a milliion years is:

http://www.nature.com/nature/journal/v399/n6735/abs/399429a0.html

Thanks Diogenes, will try to get this article.

Kenneth are these CH4 concentrations based on ice core determinations and how much of these are direct atmospheric measurements.

Thanks a lot for all the guidance you provide on these issues.

CDIAC may have what you are looking for ...

http://cdiac.ornl.gov/methane.html