New research and discovery is causing some scientists to question whether modern CO2 levels are really much different today than CO2 levels in the past.
Today CO2 levels in the atmosphere have reached some 411 parts per million. This is something like 4 one hundredths of one percent of molecules in the atmosphere. Many scientists rely on measurements taken at Mauna Loa, Hawaii since 1958. Prior to the placement of the Mauna Loa observatory, however, atmospheric CO2 levels were not systematically measured.
Consequently, scientists have looked to “proxies” to try to determine CO2 levels in Earth’s past. The most commonly consulted proxy is the content of ice cores obtained near Vostok, Antarctica.
Scientists obtain the cores by drilling down through Antarctic ice and then examining the gas content of layers of ancient ice. From this technique, some scientists have claimed that CO2 levels were generally stable across time at around 200 to 220 ppm until the Mauna Loa observations.
But there are grounds to challenge the accuracy and validity of the CO2 levels found in the ancient ice core samples as a measurement of atmospheric CO2 levels of the past.
A video by “1000Frolly,” an Australian climate scientist, points out that the ice core records may not be valid for measuring CO2. The ice core records do not correlate with other known proxy methods for measuring atmospheric CO2. (For example, records of fossilized plant stomata, which are tiny holes in plant leaves through which CO2 enters plants, seem to indicate CO2 levels were generally quite high (and quite variable) in the past.
“1000Frolly” suggests that the “Knudsen diffusion effect” may account for the seeming low levels of CO2 found in ice core samples. This effect occurs when pressure from ice pushes CO2 and other gasses to escape from the ice.