Update gvco2 field (and rename to mbl CO2?)

Reported by @AnsleyManke on 8 Feb 2013 19:45 UTC See also #1447

Here is a portion of an email thread in which Are Olsen points us to the gvco2 source to use now.

Date: Feb 8 2013 and previous. Subject: What variables to include in SOCAT v2.

On 2/8/2013 11:00 AM, Steve Hankin wrote:

On 2/8/2013 10:54 AM, Are Olsen wrote:

On Feb 8, 2013, at 5:10 PM, Steve Hankin wrote:

Thanks Are,

(STEVE) >>> Just in time. A few follow up questions here:

GlobalView CO2 is time interpolated from a monthly dataset that gets a new year appended each year. (Actually, not sure how frequently they update it.) My impulse would be to include it ... providing some kind of reference point on atmospheric CO2 has obvious value, as long as the limitations of it are clear from the variable name.

(ARE) >> I am not all that familiar with what GV looks like. If there are year-specific versions it would be nice to merge data from appropriate years into SOCAT, as far back as GV allows us to go.

Actually, searching for GV information, I came across this statement at ESRL GV page (http://www.esrl.noaa.gov/gmd/ccgg/globalview/co2/co2_version.html), "The Reference Marine Boundary Layer matrix, which was provided in previous releases, is no longer available. Instead, NOAA has made a more comprehensive MBL reference product available here. Statistical summaries of key features in measurement records are no longer included." "Here" is http://www.esrl.noaa.gov/gmd/ccgg/mbl/ - seems as if this product goes back to 2002. I am suggesting that we include this from 2002 hence forth, using the data closest in time and space, and leave the data from before 2002 without a (apparently what we now have to call ) mbl CO2 value.

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Migrated-From: http://dunkel.pmel.noaa.gov/trac/las/ticket/1502

NOAA-PMEL / LAS

Update gvco2 field (and rename to mbl CO2?) #1508