Cause and Effect. No issue is more turned upside down in the global warming debate than global temperatures and CO2 levels. That CO2 levels change during the past glacial and interglacial periods is very well documented. It has been used as the basis for climate sensitivity calculations by many warmists. There is one problem with determining the climate sensitivity based on CO2 feedback forcing. It assumes that at least some of the temperature change is caused by changing CO2 levels.
What if the reverse is true? What if CO2 levels have primarily been determined by the ocean temperature and there is no significant forcing from additional CO2 in the atmosphere? Here is what is known. In the transition from the last glacial to the Holocene interglacial, the polar temperatures increased about 12 °C, while CO2 levels increased from 185 to 265 ppm, or about 80 ppm for the comparable time frame.
It is widely accepted that CO2 is released into the atmosphere when the oceans warm, but lets take a look at exactly how much is released. This is greatly simplified because the solubility is linear from 0C to about 18C. Since this is also the primary range that is affected during the transition from glacial to interglacial I am going to use linear behavior.
Since the Earth’s atmosphere weighs 5E18 kg, the mass of CO2 at the two levels are:
(185 ppm/ 1,000,000) * 5E18 kg = 9.25E14 kg
(265 ppm/ 1,000,000) * 5E18 kg = 1.33E15 kg
So the beginning of the Holocene saw ~ 4E14 kg of CO2 emitted into the atmosphere by the oceans. All very naturally. Someone had better figure out how to get the EPA to stop the oceans from polluting like that.
Now the assumptions start to enter in. Basically I am going to assume that most of the CO2 that gets released is held in the colder polar waters. This is supported by (Martin, Basak, 2010). So an assumption that 25% of the Earth’s oceans warm by 12 °C will be the starting point. I will also limit this to the top 1 meter of water for the starting point.
One quarter of the Earth’s oceans have a surface area of 9E13 m2. Since I am only doing a rough estimate right now I will use a fixed density for the oceans at 1023.7 kg/m3. That brings the total mass of one quarter of the oceans for a depth of 1 m to be:
9E13 m3 * 1023.7 kg/m3 = 9.24E16 kg
Now it is simply a matter of plotting the CO2 that is released for each 1 °C change in water temperature.
The result is almost dead on. Simply adjusting the impacted depth from 1 m to 3.5 m describes the total amount of CO2 that was added into the atmosphere as the result of the actual temperature change. The amount of CO2 released is in fact much greater than this due to the plant growth that takes place to fill the land that thaws out by the retreating ice sheets.
If the CO2 levels are dependent on temperature, then how is it possible to determine the climate sensitivity based on CO2 forcing? It is perfectly clear that CO2 levels in the atmosphere changed directly as a result of the warming, but there is no evidence at all that the CO2 caused any of the warming. Here are the NH summer energy, temperature and CO2 are plotted together chronologically.
The warming that led to the Holocene is initiated by the increase in NH solar energy which started to increased 22,000 years ago. Several thousand years later the warming was starting in Antarctica. The warming oceans around Antarctica started releasing the absorbed CO2 into the atmosphere. Once the NH solar energy stopped increasing, so did the warming. Once the warming stopped, CO2 stopped increasing. The order of events is very clear. Changes in solar energy cause warming. Warming oceans release CO2 into the atmosphere.
In situations where there is a temperature change that involves large bodies of water below 18 °C, CO2 levels will increase with warming water and drop with cooling water. In no way does it show that temperatures changed as a result of increased levels of CO2. The correlation of CO2 levels in the atmosphere to global temperatures shows only that a change in water temperature will cause CO2 levels to change. There is no reverse evidence that changing CO2 levels in the atmosphere cause a change in temperature.
The atmospheric concentration of CO2 would appear EXACTLY the same as it does for the Holocene warming period regardless of any positive “feedback” from CO2. Based strictly on the sequence of events, the correct statement is that CO2 levels in the atmosphere are dependent on the changes to the temperature of the polar oceans. There is no dependence of global temperature on changes in CO2 levels.
It should also be noted that water above 18 °C will release CO2 as it warms, but not in the same amounts as cooler water.
Determining the climate sensitivity based on the effect of the cause is backwards and meaningless. Temperature changes CAUSE the CO2 levels to change. There is no evidence that CO2 changes causes temperature change.
Vostok Ice Core: Temperature and CO2.
Northern Hemisphere: Summer Insolation