Disputes climate change data

To the editor:

This is regarding the Spectrum piece by Norbert Chowaniec, published in the Frontiersman on March 2. Mr. Chowaniec seems to misunderstand the math concept of “percent change,” the relationship between a change in value and the beginning value.

Using the atmospheric CO2 concentrations provided of 0.0280 percent in 1800 and 0.0344 percent in 2000 gives an increase over those 200 years of 0.0054 percent (parts per 100 parts). Note that this is the concentration increase in parts per 100 parts; it is not the percent change in value. To get the percent change, divide the concentration increase, 0.0054 percent, by the concentration in 1800 of 0.0280 percent. This gives 0.192857, or 0.192856 of a part in 1 part. To convert to percentage (number of parts in 100 parts), multiply by 100, to yield 19.2857 percent, which is approximately 20 percent. Stated another way, 0.0054 (the increase) is 19.2857 percent of 0.0280 (the beginning value).

Expressing the CO2 concentrations as percent values (parts per 100) confuses the discussion. Atmospheric science usually gives gas concentrations in parts per million by volume, or “ppmv.” Converting the CO2 concentrations under discussion from parts per 100 parts (percent) to parts per million (ppm) yields whole numbers rather than small decimal fractions and eliminates using the term “percent” to describe concentrations. The conversion factor is 10,000 (1 million divided by 100). The equivalent atmospheric CO2 concentrations can then be stated as 280 ppm in the year 1800 and 344 ppm in 2000. Subtracting 280 ppm from 344 ppm, gives a difference of 54 ppm, the increase in the 200 year period. Dividing 54 by 280 gives the same decimal fraction calculated above of 0.192857, meaning 54 is 19.2857 percent of 280, or approximately 20 percent. So, when climate monitoring scientists stated that the atmospheric CO2 concentrations increased by about 20 percent between 1800 and 2000, they were correct.

By the way, the mean atmospheric CO2 concentrations measured over the last 50 years at the Mauna Loa Observatory in Hawaii, the atmospheric research facility operated by NOAA (at 11,135 feet above sea level), increased from 316 ppmv in 1959 to 387.4 ppmv in 2009, an increase of about 22.6 percent. The concentrations increased every year. See data at www.esrl.noaa.gov/gmd/obop/mlo.

James Keene

Palmer