Making reference to “An Inconvenient Truth”, the 2006 documentary written by former Vice President of the United States and climate activist Al Gore, a podcast with over 1,000 plays that is available on Apple Podcasts has claimed that the amount of carbon dioxide (CO2) usually present in the atmosphere – 417.19 parts per million (or ppm, the unit used to measure the concentration of this gas) – is a false record since “it has been significantly higher on many occasions”.
This claim is MISLEADING. While the presence of CO2 in prehistoric periods did reach up to 2,000 ppm, it does not mean that the current levels of 417.19 ppm are not a record: it is the highest amount of CO2 ever reached in the history of humanity.
Another mistake is the false current record of CO2: they say it has never been exceeded, but it has been significantly higher on many occasions
The planet is approximately 4.54 billion years old and humans appeared around 300,000 years ago. As we have already explained, the climate has undergone a number of transformations throughout this time, including a glacial maximum approximately 20,000 years ago and thermal maximum 55.8 million years ago, phenomena which have been explained, for example, by solar radiation, Milankovitch cycles or volcanoes.
There have also been periods in which CO2 levels have exceeded the current amount, as the podcast says. For example, during the Eocene – a period ranging between 56 million and 34 million years ago – there were no polar ice caps, the temperatures were roughly 10ºC higher than in the 20th century and the amount of atmospheric CO2 was roughly 1500 ppm.
Later on, less than 30 million years ago, “the levels were already beneath the threshold which allowed for the development of permanent ice sheets in Antarctica due to changes in the hydrography of the Southern Ocean, which would have increased storage of CO2 in the deep ocean”, Javier Sigró, geographer and researcher at the Centre for Climate Change (C3) of Rovira i Virgili University in Tarragona, Spain, explains to Verificat.
During the Jurassic period (between 201.3 and 145 million years ago), which the commentator talks about in the podcast, there were also elevated concentrations of carbon dioxide in comparison with today, although the amounts vary depending on the analysis. For example, according to a study published in Geophysical Research Letters in 2014, the estimates indicated that atmospheric CO2 levels reached 1,000 ppm during this period, i.e. approximately two and a half times more than the current level. Other analyses place this figure at roughly 1,500 ppm.
Sigró points out that these and other estimates of CO2 levels in prehistory are made “based on the analysis of various sources, such as marine and lake sediments (belonging to the lakes), the analysis of fossilised wood and pollen, stalactites (rocks formed on the roof by slow filtration of water with diluted calcium carbonate), and the composition of ice cores from Greenland and the Antarctic, and other things”.
CO2 levels today
Although the current CO2 levels may be relatively low in the context of the past 500 million years, the truth is that, according to NASA, these levels are much higher than at any other time in the past 800,000 years, and this increase has been predominately observed in the 20th century. “Since the start of the industrial era (in the 18th century), human activities have increased atmospheric CO2 by 50%”, according to the space agency.
Therefore, the current atmospheric CO2 levels are at a record high: not in the history of the Earth, but in the history of humanity.
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