Using a new observational approach to an old but most important question, CLINTEL President Guus Berkhout finds that about 62% of the atmospheric CO2 increase is due to natural sources, not human emissions. The study then looks at the implications for drastic CO2 reduction measures, finding that these measures will not stop the atmospheric increase. Actually, they will have very limited effect. Hence the title of the report is “Managing the Carbon Dioxide Content in the Earth’s Atmosphere“.
Professor Berkhout’s approach is based on proven technology in geophysical imaging. He calls his method spectral ‘fingerprint detection (FPD)’, because it looks at the relationship between fine-grained details of the atmospheric CO2 increase and anthropogenic emissions over time by computing auto and cross correlation functions.
Note that in the spectral FPD approach knowledge about the existence of different CO2 isotopes (C12 and C13) is not required. This is consistent with the current decarbonization practice, where minimization of the atmospheric CO2 concentration is the target, whatever the isotopic composition.
Note also that spectral FPD reveals that a lot of information is hidden in the variability of observations. Therefore, spectral FPD starts with decomposing observations into trends and changes along the trends.
The study puts it this way:
“The fine-grained variability of the anthropogenic emission represents the ‘fingerprintof the human CO2-source, telling us that most of the anthropogenic CO2-emission is absorbed by the land-ocean reservoir (fingerprint detection). It also reveals the existence of internal oscillations between the atmosphere and the land-ocean reservoir.”
There is a lot of math here, including least-squares minimization, but the results are clear. An estimated 62% of the increased CO2 concentration is entirely natural.
The study then applies these findings to determine the impact of four different emission reduction scenarios, as follows:
“Four policy scenarios for decarbonization purposes have been built: ‘Business as Usual’, ‘Stabilizing the Emission’, ‘Reducing the emission’ and ‘Making use of CCS’. A big impact conclusion for policy making is that zero anthropogenic emission – being a major achievement– does not mean at all that the atmospheric accumulation becomes zero.”
The analysis comes with a warning:
“Each scenario has its own phase diagram, showing the relationship between atmospheric concentration and anthropogenic emission. It is advised that decarbonization policies are designed such that the transition path in the phase diagram is technically, economically and socially feasible.” (Emphasis added)
Given that even the most stringent (and hugely expensive) scenario does not stop the natural CO2 increase, their rationale is greatly diminished. Also, given that most of the past increase is natural, we can stop blaming ourselves for it.
Professor Berkhout says this is just the first step in applying spectral FPD to the science of climate change:
“By considering spectral fingerprint detection on any source variability, there will be a lot of applications. Apart from CO2 variability, we will look at solar-irradiation variability, cloudiness variability, etc. to determine their individual influence on atmospheric temperature. It leads to a multidimensional causality determination. Again, without any theoretical assumptions. It is all based on observations.”
In science new methods often yield surprising results. I look forward to this multidimensional causality determination with great interest. In the meantime, the climate science and policy communities need to rethink the contribution of human emission to the atmospheric CO2 increase, especially with regard to the potentially destructive mitigation actions.