Co2 on Ice

The question that used to be asked of someone whose mental faculties were suspect was ‘who’s the Prime Minister”.  Today the question might well be “what gas causes the climate emergency?” Indeed, for that purpose perhaps, the all-knowing Google presents for us a series of mini questions and simplified answers, so that some of us elderly types (those of us who weren’t educated proper in “The Science”) can correctly answer such an important question and be deemed compos mentis:

Question: What is the relationship between CO2 levels and temperature? 

Answer: When the carbon dioxide concentration goes up, temperature goes up. When the carbon dioxide concentration goes down, temperature goes down.  

Question: Does increased CO2 increase temperature?

Answer: When there’s more CO2 in the atmosphere, it makes the atmosphere warmer by trapping heat. Since humans are adding more CO2 to the atmosphere, that helps explain why temperatures are increasing around the world.

Question: Which comes first CO2 or temperature rise?

Answer: Although the increase in temperature occurs prior to an increase in carbon dioxide, carbon dioxide plays an important role in the retreat of an ice age. As carbon dioxide in the atmosphere increases, the greenhouse effect is strengthened, and a greater degree of warming occurs.

Question: Does temperature increase before CO2?

Answer: If the temperature went down, CO2 would go down. And the reason for that is when the temperature went up, the whole biosphere revved up and emitted CO2, and we had more CO2 in the atmosphere … Increasing CO2 in the atmosphere is leading to increased temperature.

These questions and answers echo the message made famous by the Nobel Prize winner Al Gore with his enormous studio prop for Guggenheim’s infamous film – An Inconvenient Truth.  This showed temperature and carbon dioxide levels changing in tandem down the Vostok ice core from central Antarctica. But, for me, these simplified answers exemplify much that is wrong with climate science. They illustrate the rush to overemphasise any seemingly supportive evidence and to ignore the negative. I note that the Google answers are based upon evidence drawn almost entirely from polar ice cores, but nowhere is this acknowledged.  Nor is it acknowledged that the ice core data can be used to falsify the idea of CO2 as a climate driver. Furthermore, the role of the ocean as a major source and sink for CO2  goes completely unmentioned. In conclusion, we have here four questions and answers that try to keep on message with the consensus, but which actually fail miserably.

We need to take a much closer look at the ice core data and what it is telling us.

Vostok ice core data

Ice core data that were used to establish these CO2-temperature relationships do not exactly fit the alarmists’ message. If CO2 is the major control of climate change and this amplifies smaller changes caused by other weaker factors, like Milankovitch Cycles, then why the large time lags between CO2 and interpreted temperature changes in those ice cores? These questions have been rather ignored by alarmists who have focussed exclusively upon the cause of temperature rises associated with increasing atmospheric CO2 and largely ignored the relationship (if any) between falling CO2 levels and temperature.

As just stated most attention has focused on the time lag at the end of some glacial episodes between the time temperatures began to rise and a later rise in CO2 levels, an average lag of 600 ± 400 years over three cycles. This looks very much like an effect occurring before its interpreted cause.  Consequently, sceptics have tended to focus upon this relationship. But for me and a few others, like Euan Mearns (see References), it is the time discrepancy between falling temperatures and CO2 levels that is more enlightening.  The alarmist position has been to ignore the time discrepancy when temperatures and CO2 levels fall, and to argue vehemently that under normal conditions CO2 is not the instigator of climate change but instead acts as an enforcer or enhancer – making the temperature change significantly greater than it would have been. Thus slight warming is produced by small changes in solar influx (itself governed by Milankovitch cycles), probably enhanced by albedo changes. This warming then causes more CO2 to enter the atmosphere from a warming ocean, enhancing the greenhouse effect, and further warming ensues. This storyline demands that CO2 is responsible for much of the warming, but not for its initiation.

There also has been some debate about how long the time lags between temperature and CO2 changes have been. This is because the age of the ice, whence the temperature record is obtained, differs from the age of the gas bubbles within the ice, whence the CO2 and methane contents are obtained.  Snow accumulates initially and this becomes progressively more compacted (turning first to firn and then to ice) as it is buried beneath later snow. During the compaction the trapped gasses between the snow crystals are still able to diffuse and mix with the atmosphere. Thus the composition of the gas mixture within bubbles in the ice is that of the atmosphere when the bubbles become isolated and not at the time the frozen water accumulated. This may occur hundreds or even thousands of years after the frozen water that encloses the gas bubbles. Thus there is an age for the ice and a different age for the gas bubbles. In ice that has accumulated very slowly, like that cored at the Vostok drill site in central Antarctica, ice and gas bubble ages may differ by more than several thousand years.  

There have been attempts to reduce the timing difference between changes in temperature and CO2 content at the glacial-to-interglacial transition by changing the estimates of when gas bubbles become isolated. This could make the relationships more favourable to an interpretation giving more emphasis to the importance of CO2 in controlling climate.  This can be done by reducing the difference between the ice and gas bubble ages.  However, what this also does is to increase the time lag between the falls in temperature and CO2 at the beginning of a glacial stage. Messing about with the age discrepancy between the ice and its enclosed gas bubbles also upsets a strong relationship between changes in temperature and the methane content in the trapped gas bubbles. Changes in methane are closely linked with temperature changes rising and falling nearly synchronously.

Figure – 1 dT and dCO2 in early part of post Eemian Last Glacial stage.  Temperature drops more than 7 oC over a period of 14,000 years with no change in CO2 levels from their interglacial values.  Note that time progresses from right to left

The problem with investing CO2 with a major role in the rise of temperature by virtue of its greenhouse gas properties is revealed at the other end of the climate cycle – what occurs at the end of an interglacial. Here temperatures drop precipitously down to glacial levels, whilst CO2 levels remain unchanged sometimes for as long as 14,000 years in the case of the demise of the last (Eemian) interglacial (Mearns, 2017). This reveals an inability of CO2 to influence atmospheric temperatures for this length of time. If CO2 did exert an influence on temperatures then its presence at high levels at the early stages of a glacial period should prevent temperatures falling to full glacial conditions. It doesn’t. In fact the presence of interglacial levels of atmospheric CO2  during the initial stages of a glacial period, when temperatures have already fallen to low levels, strongly suggests that CO2 has no effect whatsoever. Stated differently, there is no evidence that its greenhouse gas properties have ANY effect:CO2 is not the be-all and end-all of climate change.  High levels of CO2 were unable to maintain high temperatures as the world slipped into glacial conditions, not just once but during climate cycle after climate cycle during the Pleistocene.

Importance to climate change

In olden-days, in the times of Gore, anthropomorphic climate change rested upon four easily understood planks. First that CO2 is a greenhouse gas whose presence in the Earth’s atmosphere increases temperatures. Second, that since the Industrial Revolution, and especially since the 1950s, humans have been inadvertently and significantly increasing CO2 in the atmosphere. Third, that there is a lockstep between CO2 and calculated temperatures within polar ice cores revealing the importance of CO2 as a driver of temperature changes, and lastly Present-day CO2 levels are substantially higher than they have ever been during the entire period recorded in the ice cores. These easily understood planks were (and are still are) the basis for the belief in Anthropomorphic climate change and led to Catastrophic anthropomorphic climate change (aka the Climate Emergency) and demands for humongous changes in our lifestyles. Yet a simple examination of the relationships between temperature and atmospheric CO2 levels in Antarctic ice cores suggests that two of these planks are decidedly wrong – there is no precise lockstep between changes in temperature and atmospheric CO2 contents recorded in Antarctic ice cores at the beginning of glacial periods, and for many thousands of years at these times there is no evidence supporting the case that changes in CO2 content had any greenhouse effect. This last point is a real puzzle because there is much evidence that CO2 is indeed a greenhouse gas.

Two of the planks remain unbroken. Humans have increased atmospheric CO2 and to levels unmatched in the previous four interglacials but it is more difficult to support the case that our CO2 emissions constitute a threat.  

Nevertheless the old chestnuts are still alive and cooking. Despite the evidence from Antarctica, a drop in CO2 in the northern hemisphere is being blamed for the advance of ice sheets at the beginning of the last glacial period (Willeit et al., 2015). It is scarcely believable that a drop in CO2 causes temperature drops sufficient to cause glaciation in the northern hemisphere but had no recordable effect in the Southern Hemisphere for 14,000 years. But such is what we are being asked to believe. What is a sceptic (or even a warmista) to believe? Finally alarmists that seek a silver lining, that high CO2 levels might ameliorate a forthcoming ice age, are bound to be disappointed.

Note that this article only re-examines the possibility, based upon evidence from the Antarctic ice cores, that atmospheric CO2 controls global temperatures by virtue of its greenhouse gas properties and finds that possibility to be without merit. It does not speculate about the sources and sinks that release and absorb this gas. For those see Mearns 2017.

References:

From snow to firn to glacier ice. AntarcticGlaciers.org

Fischer, H. et al., 1999, Core Records of Atmospheric CO2 Around the Last Three Glacial Terminations, Science. 283, 1712-1714.

Euan Mearns, 2014, The Vostok Ice Core: Temperature, CO2 and CH4, Energy Matters.

Euan Mearns, 2017, The Vostok Ice Core and the 14,000 Year CO2 Time Lag, Energy Matters

Willeit, M., Ganopolski, A, Calov, R., Robinson, A. and  Maslin, M., 2015, The role of CO2 decline for the onset of Northern Hemisphere glaciation, Quaternary Science Reviews, 119, 22-34

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July 7, 2021 at 11:27AM

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