Monthly Reading on CO2 Atmospheric Concentration

The graph above shows the monthly CO2 atmospheric concentration reading collected at Mauna Loa (19°28′46.3″N, 155°36′09.6″W), North Hemisphere. The CO2 fluctuation pattern is consistent thoughout the year: rising high in the month of April-June and decrease in August to October, and September being the lowest point. Hmmm, why more CO2 is released in April (spring time) and CO2 is absorbed or taken away from atmosphere in September (autumn)? The decomposition of plant at the end of autumn or beginning of winter should explain the increasing CO2 trend starting from November, especially for north hemisphere.  

The steady increment of CO2 atmospheric concentration reading is also noted as the year increase. For example, the highest peak of CO2 reading in 1996 is 365.41 ppmv (April)  while lowest valley point is 359.46 ppmv (September). Two years later in 1998, the value of CO2 raised to 369.29 ppmv for the peak point while 363.9 ppmv is read in September, the lowest point in the year. An increment of 3.88 and 4.44 ppmv is recorded in April and September respectively. Thus, an average of 2 ppmv of CO2 is added annualy, or roughly 1.59E+10 tonnes in weight.

Next, the variation of month to month comparison is compared for the 10 years period, at the site of Maona Loa. Within a year itself, the range of CO2 atmospheric reading (highest and lowest recording point) is about 5.20 to 6.60 ppmv. By converting the concentration value in ppmv, the weight of CO2 is calculated (like example here). The weight of CO2 is listed in the table below:

As we see the values above, each year there is a huge amount of CO2 is fluctuating in the  atmosphere. It might look small in concentration reading (as small as 5-6 ppmv), but in terms of weight,  it is almost 2-2.5 times of human activity related CO2 emission: 2.413E+10 tonnes.

Another comparison is made as well. There are 10 sites recording the CO2 atmospheric concentration, as listed previously here. The average reading of one year recording at each site is compared to other 9 locations. The range of the reading is as big as 4.44 ppmv among these locations around the world. Translating this concentration number into CO2 weight, a difference of 2.931E+10 (or 29.31 billion) tonnes to 34.70 billion tonnes of CO2 is noted. Again, this number is exceeding the anthroprogenic CO2 emission (24.13 billion tonnes).

source: CDIAC

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