Every once in a while there is a warmist story that gets more play than average. My very scientific method of determining how many people are reading such news is based on how many relatives ask if I saw it. When the long lost relatives send me an email, then I know a lot of people saw the news. Ok, that isn’t really scientifically rigorous, but I like it anyway. This one however got onto the SkS webpage so I decided to put together a response.
The issue at hand is the initiation of the ice age in Antarctica that took place ~34 million years ago. This is a big event geologically speaking as the world’s sea level dropped dramatically and the climate in many places around the world changed. It is so big that it marks the end of the Eocene period and the beginning of the Oligocene period. There is a bit of information in the book about this period, so this is not a new topic of study.
The new news that broke over the past month was a study by Pagani that states that a global drop in CO2 is what caused the ice age in Antarctica to start. There is nothing new about this proposal, but for some reason this got more attention than most such studies. Perhaps that is due to the release a few weeks before the Durban climate meetings (which I ignored for good reason).
It used to be settled science that it was the opening of the Drake Passage that created the Antarctic Circumpolar Current (ACC) that prevented the warm tropical ocean currents from reaching Antarctica and this is what caused the initiation of the current ice age. The timing fits and for a long time this was the “settled” science. The warmists have found an angle to fight back with and they use the fact that global CO2 levels dropped at the same time as “proof” that it was CO2 that caused the ice age to initiate. It seems that every six months there is a paper for the Drake Passage theory and then six months later there is one to push the CO2 theory. Since the last Drake Passage paper came out in May, late November would be the six month mark, like clockwork. I covered the last Drake Passage news on May 30th, 2011.
The new news presents nothing new. Here is the end of the abstract:
Our results show that CO2 declined before and during Antarctic glaciation and support a substantial CO2 decrease as the primary agent forcing Antarctic glaciation
This proves nothing about the debate itself, it simply shows that the climate was changing at the time that Antarctica started it’s ice age. This is well known, because it was at this time that the Earth’s geography was changing enough to alter the ocean currents.
The major flaw in all CO2 studies is that changes in ocean temperature ALWAYS cause changes in the atmospheric CO2 concentration. It is not possible that a major change in ocean temperatures will not cause a major change in the CO2 level. The Southern Ocean is 20.3 million km2 in size which is ~6% of the Earth’s oceans and ~4% of the total Earth’s surface.
I am going to start by showing how much CO2 the top 1 m of the Southern Ocean can make to the global CO2 level. The 20.3 million km2 of ocean turns into 20.3 e+13 m2 of ocean. Since the lower range of sea water density is 1020 kg/m3, it is easy to figure out the weight of the top meter of the Southern Ocean at a 2.07 e+16 kg. The average temperature of the Southern Ocean today is 5 °C which means that at saturation, the top 1m of the Southern Ocean could hold 6.0 e+13 kg of CO2. That is 1.9% of the Earth’s total atmosphere. Since for most changes in ocean temperature it is the top 100 m that is considered, the top 100m of the Southern Ocean could hold 190% of the Earth’s atmospheric CO2.
Here is where the true absurdity of the latest study that claims it is the CO2 level that caused the Earth’s climate to change 34 million years ago. A 10 °C change in 100 m of the Southern Ocean could cause a 50% drop in the global CO2 level.
Since the solubility of CO2 is linear from 0-20 °C, it doesn’t even matter what the starting temperature was, all that is needed is to know how much the temperature of the ocean dropped.
Perhaps the most interesting thing of all is that the paper states that the CO2 prior to the ice age initiation was 1000-1200 ppm and afterwards it was 600-700 ppm. Somehow the idea that the cooling of the Southern Ocean by 10 °C would CAUSE a 50% drop in atmospheric CO2 is completely missed by the warmists. The warmists do not propose what would cause anything, except for the idea that a drop in CO2 caused the drop in temperature. This is very bad science.