On the Poor Correlation between Atmospheric CO2 Levels and Average Global Temperatures
Over the years and another blog, I wrote some posts about why the popular gospel of anthropogenic climate change was a form of secular apocalypticism whose origins can be traced to the ongoing terminal demise of the West. However I never got around to writing a proper and in-depth series about that topic, until now. My biggest concern about writing such a series was its potential length and the necessity of explaining many concepts over its course. But it gradually became obvious that 'kicking the can down the road' was not a viable long-term strategy. So, I have decided to start writing it- even if the results turn out to be, initially, less brilliant than hoped for.
With that out of the way, let me quickly describe the structure of this series. While it would have been better to first tackle the psychology and mindset underlying belief in anthropogenic climate change, doing so would result in a series of long posts which were unlikely to capture the reader’s interest. Instead, I will mix up posts about the interpretation of scientific evidence with others about related psychological concepts. The first couple of posts in this series will be about the lack of correlation between atmospheric concentration of CO2, average surface temperature of earth and mass extinctions over past 550-600 million years of geological history.
But before we go there, let us be clear about a few things. Measuring atmospheric CO2 directly and accurately is only possible if you have an actual sample of the atmosphere. All measurements of atmospheric CO2 from the past are, therefore indirect- albeit to varying degrees. For example, while it is possible to measure CO2 dissolved in ice core samples, the numbers have to adjusted for the atmospheric temperature at which the tested snow originally precipitated using isotope analysis, because the solubility of CO2 in water and ice is temperature dependent. Ice core measurements, in contrast to other methods, do have good temporal resolution.
There is however a upper-age limit to using ice cores and the oldest one, we are somewhat certain about, is about 2.7 million years old. Also, there may be a hard limit on how far we can go back with ice cores since many parts of mainland Antarctica within 483 km (300 miles) of the south pole were seasonally ice-free as late as 2.6 million years ago. In the next part of this series will explore how those parts of Antarctica were 30 degrees Celsius warmer than today, even though the atmospheric CO2 levels were not that different. Measuring atmospheric CO2 from a time before 2 million years requires different, and even more indirect, methods of measurement.
Without going into too much detail here (you can always read the source paper), this category of methods is based on atmospheric CO2 being correlated to preferential weathering of certain minerals in rocks (through rain) and carbonate deposition in the oceans. It also factors many other things from stable isotope measurement of certain elements in dated rock and soil samples, size and position of continents in the past, outgassing through known large-scale volcanic activity and many others to estimate the amount of CO2 in the atmosphere.
The relevant part is that this method, even in its crude older form, gives an acceptably accurate measurement of CO2 levels in the atmosphere upto 600 million years ago. Yes.. the error margins can be upto 50% of the measurement, but it is still good enough to tell us that the earth used to have far higher atmospheric CO2 in the past. Reconstruction of average surface temperature during these eras is based on fossils records of plants and animals, various isotopic ratios and recreating positions of landmasses using paleomagnetic data.
But how much higher were the CO2 levels? Well.. they were almost 20 times higher than today in Cambrian era and about 10 times more during the Ordovician. And it remained in the 8-12 x range for the Silurian and Devonian. Notably, these were the four geological ages when most animals and plants lived in or near oceans and other water bodies. It was also the heyday for Mollusks and shelled Cephalopods. Evidently, all of that “excessive” atmospheric CO2 had no negative effect on the oceanic pH.
More curiously, the Ordovician-Silurian (O-S) extinction was largely due to a short spell of global glaciation. And this global ice age occurred when CO2 levels were over 12 times higher than today. It was only in the late Devonian (after plants had finally established themselves on land) that atmospheric CO2 levels started to fall, and there was another moderate sized extinction towards the end of that age. The next age, Carboniferous, saw a massive expansion of plants of land and resulted in a further decrease in atmospheric CO2 until it was about 2-3 times current levels. It was also the age of high oxygen levels and giant insects.
Atmospheric CO2 levels during the Permian remained low for millions of years but then started to go up. The end of this era saw two very closely spaced and massive extinctions, the End-Capitanian and Permian-Triassic aka 'The Great Dying'. While CO2 levels went up to about 4-5 times today, temperature increases (especially in tropical and sub-tropical oceans) were insane. There is evidence that the temperature of ocean water at surface in subtropical regions exceeded 40 degrees Celsius for a few hundred thousand years. While temperatures did fall afterwards and life recovered, they remained pretty high by current standards. However the climate eventually became wetter, especially after the Carnian Pluvial Event.
The Triassic-Jurassic extinction ended the Triassic and ushered the Jurassic. That geological age saw an increase in atmospheric CO2 but no accompanying rise in average surface temperature. While forests on earth never reached the density and levels they did during the Carboniferous, the Jurassic comes a semi-close second. Earth transitioned into next age, aka Cretaceous, with only a few minor and small extinctions. Initially the cooling seen during the late Jurassic continued, but soon reversed itself and it became almost as warm as the middle-Jurassic. The Cretaceous was also the longest geologic age since the Cambrian explosion and lasted about 145 million years. Atmospheric CO2 levels slowly declined to about 2-3 times today, in spite of the temperature remaining fairly high and constant. Isn't that odd?
The Cretaceous ended with the Cretaceous-Tertiary/Paleocene extinction. After that the earth recovered from it the climate was still pretty warm and humid. Then we had the Paleocene–Eocene Thermal Maximum at around 55 million years and for about 200 k years it so warm in higher latitudes that Palm trees grew in Washington State and Southern Canada. Then around 45-35 million years ago, there was another round of cooling and a further slight decrease in atmospheric CO2. However temperatures went up again between 35 and 6 million years ago. The most recent round of global cooling began about 6 to 7 million years ago when a land-bridge between north and south American continents started to form between southern tip of what is today Mexico and northern tip of Colombia. This bridge slowly started to cut off equatorial connection and circulation between the Atlantic and Pacific.
Once that land connection was fully formed about 2.6-2.3 million years ago, global temperatures dropped even further and we started having regular and long ice ages (after almost 300 million years) with brief inter-glacial warm periods. This is also when a lot of tropical and sub-tropical whale species and large marine mammals went kaput and consequently took out predators such as Megalodon. Did you notice that the drop in atmospheric CO2 cannot explain the current stretch of ice ages started around 6 million years ago, nor why they intensified in past 2.3-2.6 million years. Are you beginning to see why I think that the whole anthropocentric climate change theory is bullshit. In not, there is more material in upcoming posts under this topic.
What do you think? Comments?