Yes you found it! Thanks! That saves me from doing expensive (and again: very anti-entrepreneur-spirited (from now on abbreviated simply as VANTEN-spirited or VANTENS) calls to oversea!


In fact I found now also in addition that Dr. Dlugokencky has a ftp server where the Mauna Loa files naming conventions seem to be explained:
ftp://ftp.cmdl.noaa.gov/ccg/ch4/in-situ/README_surface_insitu_ch4.html. In that file it is written that:


>[parameter]_[site]_[project]_[lab ID number]_[measurement group]_[optional qualifiers].txt

and since I had also found this page:
http://www.esrl.noaa.gov/gmd/dv/iadv/

I was able to learn that the site abbreviation "MLO" seems to mean Mauna Loa, so the file you linked to:

ch4_mlo_surface-insitu_1_ccgg_month.txt

seems to provide -if we assume that this naming convention applies also to this file- indeed a measurement of CH4 at the site Mauna Loa by the measurement strategy "surface insitu" (which I guess is some surface measurement?) by lab nr. 1 by the measurement group ccgg and the data displays the "Computed monthly mean values"

Then in the explanation file one finds the fields explained:

and field 6 is

>Dry air mole fraction. Missing values are denoted by -999.99[9].

So I guess one should assume that the numbers in the file you linked to are some mole fractions which are probably
the number of molecules of CH4 divided by the number of molecules of dry air found in one fixed volume.
Do you see this similarily?


>By the way - it’s interesting to see that the concentration of methane in the air depends a lot on the latitude!

click for details ?

it looks as if the graphics doesn't show the southern hemisphere - I could imagine that it is somewhat symmetric with respect
to north and south (i.e. that it would ascend again, where the word "global methane" is.)
The rise per latitude seems to be at least partially due to circulations. ?

>What do you want to compare about methane and CO2, Nad?

I actually wanted to compare the methane and the CO2 and the temperatures and eventually look if I can find anything
which can be remotely be called a time lag but I fear there is not enough data for that. The methane measurements are there only
since about 20 years.