May 10 Comment: NOAA has reported 400.03 for yesterday, but Scripps has reported 399.73. The difference is similar to other differences we have reported. The difference partly reflects time zone differences. NOAA uses UTC, whereas we use local time in Hawaii to define the start and stop of a given day. Changing to UTC excludes the lower CO2 period from the baseline on the May 9, shifting it to May 10.
The remaining baseline data then averages 400.08 for May 9.
May 7 Comment: Starting around May 1, we began experiencing intermittent difficulties with the computer used to control the Scripps CO2 analyzer at the Mauna Loa Observatory. This led to delays in providing daily values and also some data gaps. Although such difficulties are not uncommon and rarely lead to significant long-term data loss, we have decided to switch over to reporting daily values from second Scripps instrument, operated in parallel at Mauna Loa in collaboration with Earth Networks Corp.
Starting with the May 6 daily value, we are now reporting values from the second instrument. This second instrument was installed in Dec. 2012, and since then the two instruments have agreed well. The second instrument has not been experiencing the same sort of computer difficulties, allowing for more reliable daily updates. We are in the process of troubleshooting the first instrument, and plan to keep both instruments operational until a full year of overlapping data is obtained. The plan is to retire the first instrument at the end of 2013.
The daily average CO2 values are computed from hourly data, retaining data when the readings are stable for periods of several hours or more. If the hourly readings on a given day are too variable, a daily value will not be generated. More information on baseline data selection can be found on the Scripps CO2 program website.
Normally, the data is downloaded from the station every day around 5:00 A.M. in Hawaii. The data for the previous day is then processed to incorporate calibration information and screened to compute the daily value. If all goes smoothly, this information is then automatically posted.
Problems with the hardware, software or data transmission from Mauna Loa to Scripps may occasionally result in the temporary or permanent loss of CO2 data. Lost data will result in gaps appearing in plots of CO2 concentrations as well as possible delays in posting updates.
Network problems occasionally interfere with the raw data transmission to Scripps, temporarily resulting in a delay in receiving daily updates. However, since the data is permanently stored on the control PC at Mauna Loa, missing data is automatically re-sent during the next data transmission once network connection resumes so that these data are not permanently lost. Thus apparently missing data from the end of the record may be restored later once data connection resumes.
Hardware failures require intervention of personnel at the NOAA facility at Mauna Loa. However, with the laboratory being in such a remote location, personnel are typically only available to make adjustments during working hours on weekdays.
– Stephen Walker, Scripps CO2 Group