BY JOSE PALU-AY DACUDAO
CARBON Dioxide (CO2) is always in the news for being the most common greenhouse gas. I have already discussed it in previous articles. Due to its notoriety, let’s discuss it again, its theoretical history. This is a review article with some new ideas.
Carbon Dioxide’s recent history
This is pretty well-documented since CO2 atmospheric studies began in March of 1958 in Mona Loa Observatory in Hawaii, a weather station of the U.S. Weather Bureau, and since then all over the world. The measurement was 315 ppm in 1957. It has been hypothesized that CO2 pre-industrial level was 280 parts per million, but this is not documented by concrete measurements. In my opinion it’s safest to assume a figure of about 300 ppm in the early 1900s.
In 28 January 2024, Mona Loa measured atmospheric CO2 at 422 ppm.
In contrast, during the end of the Cretaceous Period when non-avian dinosaurs last walked the Earth, CO2 atmospheric level is estimated to have risen to more than 1,000 ppm at one point 90 million years ago at the Cretaceous Thermal Maximum. Note that at this time of high CO2 and heat, there was a surge in speciation and biodiversity. Some of the most famous kinds of dinosaurs, such as the large carnivorous two-legged theropods as exemplified by the later Tyrannosaurus had their origins at this time.
The most recent geological era, the Cenozoic saw a cooling of Terra. It consists of two Periods, the Paleogene from the extinction of non-avian dinosaurs, 66 million years ago, and the Neogene, 23.03 million years ago to the present. It is estimated that CO2 levels during the Paleogene ranged around two times today’s Neogene (our present Period since 23 million years ago, wherein CO2 levels hovered around 300 ppm, except during the Paleocene–Eocene Thermal Maximum).
The Palaeocene is a geological Epoch of the Palaeogene Period of the Cenozoic Era that lasted from 66 to 56 million years ago. The Eocene Epoch lasted from about 56 to 33.9 million years ago. The time span between these two Epochs was remarkable for a surge in CO2 levels and Terra’s temperature.
CO2 levels at this time zoomed to an estimated 650-3500 ppm. Sea temperature in the tropics is estimated to have risen to 36 centigrade. In Antarctica the minimal temperature was 15 C.
Caveat: these studies of ancient temperatures are usually based in the isotopes of Oxygen, Carbon, Nitrogen, and Sulfur. They are inexact, thus the wide range that crop up in different studies. What we can definitely say is that atmospheric CO2 in ancient times was definitely higher than that of today’s. The farther one goes back in time, the higher atmospheric CO2 and global temperature are.
A question is: was this a disaster for biodiversity? (To be continued)/PN
