On the week of March 13 - 19, 2016 , at Mauna Loa the measured, pretty reliable, average of CO2-portion in the atmosphere was 404.74 ppm, some 3.72 ppm more than on the week of March 13 - 19, 2015 when at Mauna Loa the measured, pretty reliable, average of CO2-portion in the atmosphere was 401.02 ppm. The March 13 - 19, 2016 , at Mauna Loa the measured, pretty reliable, average of CO2-portion in the atmosphere was also some 21.87 ppm more than on the week of March 13 - 19, 2006 when at Mauna Loa the measured, pretty reliable, average of CO2-portion in the atmosphere was 382.97 ppm.
Using the larger unit, as in "0,40474 ‰", is likely not yet warranted since the current CO2-portion in the atmosphere at Mauna Loa would round to zero, if we would be capable of using just the cardinal numbers, as in "one, two, three...", etc. But it must be noted that a skilled speaker or another kind of performer may excite a crowd of very large cardinal number of people to doing or not-doing things. The inverse of the current CO2-portion in the atmosphere at Mauna Loa is ~2471, so you may imagine a Justin Bieber-concert, where this kind of thing might be going on.