Ah, the source I got used to has also continued weekly reports. Personally, I think there's little point in recording daily values wrt climate and ocean state around Hawaii, so I'm glad to see this continued, thank you Scripps for sharing data.
Last Week January 22 - 28, 2017 406.48 ppm
1 Year Ago January 22 - 28, 2016 403.12 ppm (+3,36 ppm)
10 Years Ago January 22 - 28, 2005 383.91 ppm
Comma-separated weekly values of data up to 2016/12/31 maybe found at http://scrippsco2.ucsd.edu/assets/data/atmospheric/stations/in_situ_co2/weekly/weekly_in_situ_co2_mlo.csv
for those who want to check various things about ENSO state influence on CO2-levels thereby spreading the influence of tidally (thus Lunally) driven complex primary oscillator of Current Earth heat transportation system (See Pukite model of ENSO), I gladly leave the MJO to the experts, I think it's a 'freewheel' between continentally restricted 'ENSO ocean shaker' and the completely (well mostly) tidal QBO causing the tropical weather forecasters some difficulties. That the QBO skipped a beat is a fact that should be explained ("GDI!" doesn't apply in science as an explanation, though).
As the El Nino-phase of ENSO throws up a whole bunch of greenhouse gases (almost only CO2 and H2O), which are pretty easily spread out over a whole hemisphere, I'd say the effects of a specific El Nino might remain at least two years on some specific locations.
As the tides may be a bit suppressed on areas with sea ice, the disappearance of Arctic Sea Ice may lead to related changes elsewhere in the ocean system as well, maybe even on ENSO, but I can't say this for certain. The Baltic has no tides to speak of, so no personal experience on this, additionally the tides (and the associated Ekman? Pumping on coasts due friction with continental shelves) move the whole water column somewhat, as opposed to waves which mix up only the top 20m (approx.).
Hmm, should check many things of the above but hearing 11000 Finns are banned from entering DSM because of a... ...no I'm not going to that. Comments welcome on the sciency bit. Preferably on some other thread as this is the Mauna Loa CO2 thread, I don't know why I started to write this up here. Sorry for OT.