Why does CO2 Earth focus on CO2 readings from Mauna Loa?
CO2 Earth features measurements of CO2 that scientists make at the Mauna Loa Observatory (MLO) in Hawaii, USA. There are many reasons.
First, CO2 readings from Mauna Loa are direct observations of the Earth system. They are precise measurements of the air made at one location in the Earth's atmosphere. They are not projections, estimates or averages that use advanced mathematics to generate a daily number. CO2 Earth was created to make it easy for non-scientists to see changes of consequence to the planet as they happen. Whether the CO2 problem is getting worse or getting resolved, people deserve to have access to objective informaiton without filters and delays. For this reason, CO2 Earth use data from direct observations when it reports the latest available CO2 levels.
This brings us to another reason. Unlike CO2 readings from other observing stations in the world, CO2 readings from Mauna Loa are practically real time.
A third reason relates to reliability. CO2 readings are available from not one, but two scientific institutions: NOAA ESRL (Global Monitoring Division) and the Scripps Institution of Oceanography at UCSD (Scripps CO2 Program). Each institution measures CO2 readings with separate instruments and reports their readings indepndently of the other. Scripps started continuous measurements at Mauna Loa in 1958. The NOAA-ESRL program started in 1974.
Fourth, the Mauna Loa CO2 record is the the world's longest, continuous record of observations using high precision instruments. Observations today can be compared against observations at the same location over a period of time that is longer than any other.
Fifth, year-over-year comparisons of Mauna Loa CO2 gives people a signal of planetary significance. It's true that Mauna Loa is just a spot on the map. But the year-over-year trend in the Mauna Loa CO2 is essentially the same as the trends at other observing stations. “CO2 is rising everywhere, and at about the same rate” (Volk, 2008, pp. 39-41). Further, the CO2 data presents a trend that is so clear that statistical analysis is not needed to detect it (Tans & Bolin, 2006, p. 329).
And then there is the Mauna Loa Observatory and its remote location in the middle of the largest and deepest ocean on the planet. It is 3,400 metres above sea level on a slope about 3/4 of a kilometre metres below the top of the tallest mountain on Earth. (McGee, 2017, p. 99) NOAA-ESRL states that "the undisturbed air, remote location, and minimal influences of vegetation and human activity at MLO are ideal for monitoring constituents in the atmosphere that can cause climate change (NOAA-ESRL, GMD, 2020)."
Do volcanic emissions affect CO2 readings at Mauna Loa?
Most of the time, the observatory experiences “baseline” conditions and measures clean air which has been over the Pacific Ocean for days or weeks. We know this because the CO2 analyzer usually gives a very steady reading which varies by less than 3/10 of a part per million (ppm) from hour to hour. These are the conditions we use…
We only detect volcanic CO2 from the Mauna Loa summit late at night at times when the regional winds are light and southerly. Under these conditions, a temperature inversion forms above the ground, and the volcanic emissions are trapped near the surface and travel down our side of the mountain slope. When the volcanic emissions arrive at the observatory, the CO2 analyzer readings increase by several parts per million, and the measured amounts become highly variable for periods of several minutes to a few hours. In the last decade, this has occurred on about 15% of nights between midnight and 6 a.m.
These periods of elevated and variable CO2 levels are so different from the typical measurements that is easy to remove them from the final data set using a simple mathematical “filter.”
This answer is from a 2010 article by the NASA Earth Observatory. Read the full article on the NASA website: How do scientists know that Mauna Loa’s volcanic emissions don’t affect the carbon dioxide data collected there?
Skeptical Science Mauna Loa is a Volcano
NOAA-ESRL Mauna Loa volcanic emissions: 1958 - present
USGS Hawaiian volcano observatory weekly update
Why are seasonal CO2 fluctuations strongest at northern latitudes?
Latitudinal differences in fluctuation are the result of photosynthetic activity by plants. As plants begin to photosynthesize in the spring and summer, they consume CO2 from the atmosphere and eventually use it as a carbon source for growth and reproduction. This causes the decrease in CO2 levels that begins every year in May. Once winter arrives, plants save energy by decreasing photosynthesis. Without photosynthesis, the dominant process is the exhalation of CO2 by the total ecosystem, including bacteria, plants, and animals.
This answer is from a 2013 article by Bob Monroe. Read the full article at the Scripps UCSD Keeling Curve site.
How do scientists measure CO2 levels at Mauna Loa?
NOAA How scientists measure background CO2 levels on Mauna Loa
How do scientists compute daily averages?
Scientists compute daily averages from selected hourly values that meet defined standards. Daily averages are used to calculate weekly and monthly averages.
Why did a CO2 reading change at CO2.Earth?
CO2 Earth publishes the latest data that scientific institutions (including NOAA and Scripps) have made public. On occasion, this means that a reading changes because the source institution has updated it.
Scientific institutions refer to measurements within the past year as preliminary as they are subject to quality checks. Adjustments are not uncommon but usually small.