An evidence-based approach – Are you satisfied with that?

From Climate, etc.

by Joachim Dengler and John Reid

A new look at the atmospheric carbon budget.

Climate science is often concerned with the question “How much CO₂ still in the atmosphere?”, due to anthropogenic emissions and the limited ability of the oceans and biosphere to absorb excess CO2.₂ concentration. This has led to conclusions of the kind that a certain increasing portion of man-made emissions will remain in the atmosphere forever. The commonly used concept of “fraction in the air,” which is the fraction of anthropogenic emissions remaining in the atmosphere, seems to suggest this.

We shift the focus of attention by posing the logically equivalent question “How much CO₂ does not exist in the atmosphere? Why is this so different? amount of CO2₂ does not exist in the atmosphere can be calculated from direct measurements. We don’t have to deal with each mechanism of absorption from the atmosphere into the oceans or plants. From the known global concentration changes and the known global emissions, we have a good estimate of the actual total annual absorption. They are related to CO₂ concentration, promoting the guiding hypothesis for a linear absorption model. It turns out that we don’t need to know the actual coefficients of the individual absorption mechanisms—just assuming their linear dependence on current CO is enough.₂ concentration.

Here is a short summary of a recently published articlewhere all the sentences presented here are derived in detail and backed up by references and mathematical models.

Conservation of CO . mass₂

As in the bank account, the CO2 balance in the atmosphere is the result of total emissions reduced by total absorption:

Concentration growth = Emissions – Absorption

Total emissions (in blue) exceed the annual growth in CO2 concentrations (green), indicating an increasing capacity to effectively absorb (red) with increasing CO2 concentrations:

The assumption of approximate linearity of the relevant absorption processes is shown by a scatter plot, relating the effective CO2 absorption to the CO2 concentration.

We find a long-term linear dependence of effective absorption on atmospheric CO2 concentrations with a significant short-term bias, where the effective zero absorption curve intersects at appr. 280 pages/minute. This is considered the pre-industrial equilibrium CO2 concentration, in which annual natural emissions are balanced by annual intakes. The average annual absorption is appr. 2% CO2 concentration in excess of 280 ppm. Since data before 1950 has a large uncertainty, the following calculations are made based on data after 1950, resulting in a slightly smaller absorption rate of 1.6%.

CO . gas₂ concentration as a temperature proxy

When we make predictions with hypothetical future CO2 emissions, we don’t know future temperatures. Without going into the problematic discussion of how strongly CO2 concentration affects temperature, we assume a “worst case” of the ability to fully predict the effects of heat. according to CO2 concentration.

Without making any assumptions about C->T causality, the estimated functional dependence of the temperature representation from the regression on the CO2C concentration was found to be:

t_Authority = -16.0 + 2.77*log(C) = 2.77* log(C/(235ppm))

This corresponds to a sensitivity of 1.92°C.

official form

The model with the assumption of constant absorption parameter and constant natural emissions is tested with predictions of CO2 concentrations 2000-2020 based on emissions data from 1950-2020 and Concentration data from 1950-2000.

This is an excellent prediction of concentrations on the basis of emissions and the modeling assumptions above. There are only small obvious differences between the predictions and the actual data. Although the model allows for changes in absorption levels over time, the data for the last 70 years, is a period of large amounts of man-made CO.₂ emissions, leading to the conclusion that CO₂ Absorption parameter has no significant temperature or other time dependent component and CO current₂ The emitted pulse is absorbed with a half-life of 42 years.

Future emission scenario

The most likely future emissions scenario is the IEA policy emissions scenario with approximately constant, slightly reduced global emissions. The data set to be used practically for a realistic future prediction is generated by extrapolating the trend of stated policies after 2050 and assuming that land use changes

the data will follow the current trend and drop to zero by 2100. Emissions will not fall to zero by 2100, but will remain close to 2005 levels.

Predicting CO in the future₂ Concentration

From this realistic emission scenario, future CO2 concentrations are recursively predicted with our model.

With the stated policy scenario of the IEA, i.e. no special CO2 reduction policy, the equilibrium CO2 concentration is approx. 475 ppm will be achieved in the second half of this century. Based on the empirical CO2 temperature representation equation above, this increase in CO2 concentration from 410 ppm (2020) to 475 ppm corresponds to a temperature increase of 0.4 _C from 2020 or 1.4° C since 1850.

In conclusion, we can expect maximum CO2 levels of approximately 475 ppm in the second half of this century. At this point, emissions will be fully balanced by absorption, which is by definition a “zero-zero” situation.

Assuming the unlikely worst-case scenario is that CO2 concentrations are fully responsible for all global temperature changes, then the maximum expected global temperature increase due to the projected increase in CO2 concentrations is ant is 0.4 _C from now or 1.4°C since the beginning of industrialization.

So, if we keep living with CO as we are now₂ emissions – and an efficiency improvement of 3%/decade, the Paris climate targets will be achieved.