From the blog of Dr. Roy Spencer
by Roy W. Spencer, Ph.D.
This is an update of my carbon budget model, which explains Mauna Loa’s annual atmospheric CO2 concentrations since 1959 using three main processes:
- an anthropogenic source term, mainly from the burning of fossil fuels
- a constant annual CO2 sink rate (removal) of 2.05% of the atmospheric “excess” above 295 ppm
- an ENSO term that increases atmospheric CO2 during El Nino years and decreases during La Nina years
The carbon budget model
I have described the CO2 budget model here. The key new finding was that the model showed that after cleaning up the history of El Nino and La Nina activities, the rate of CO2 sinking has not declined as claimed by carbon cycle modellers.
If the rate of sinking has really been declining, that means the climate system is becoming less and less able to remove “excess” CO2 from the atmosphere, and future climate change will (of course) be worse than we thought. But I have shown that the decreasing sink rate was just an artifact of the history of El Nino and La Nina activity, as shown in the figure below (updated to 2022).
The model also showed how the eruption of Mt. Pinatubo resulted in a sharp increase in the rate of CO2 removal from the atmosphere due to increased photosynthesis from more diffuse sunlight (not a new finding). This contradicts the popular belief that volcanoes are a major source of atmospheric CO2.
I attempted to publish the results in the Geophysical Research Letters and after review was accepted with reservations. But the editor wanted more reviewers, which he found, who then rejected the paper. The model is simple, physically consistent, and consistent with the observed Mauna Loa CO2 record, as shown in the diagram below.
Update 2022: CO2 continues to rise despite the turnaround in renewable energies
As I mentioned earlier, the global economic downturn caused by COVID had no measurable impact on Mauna Loa’s atmospheric CO2 record, and that’s not surprising given the large annual variations in natural CO2 sources and sinks. Atmospheric CO2 concentration continues to rise, mainly due to emissions from China and India, whose economies are growing rapidly.
The chart below zooms in on the period 2010-2035 and shows Mauna Loa’s CO2 increase compared to my budget model using 3 Energy Information Administration scenarios (blue lines) and also compared to the RCP scenarios used by the IPCC in the CMIP5 climate model comparison project.
The observations are below the RCP8.5 scenario, which assumes unrealistically high CO2 emissions but still remains the basis for widespread claims of a “climate crisis”. Observations over the last 2 years are slightly above my model and only time will tell if this trend continues.
But the international efforts to reduce CO2 emissions do not seem to show any obvious effects. This is not surprising as global energy demand continues to grow faster than new sources of renewable energy can make up the difference.