From Dr. Roy Spencer’s Global Warming Blog
July 18, 2022 by Roy W. Spencer, Ph. D.
Summary
The simple CO2 budget model I introduced in 2019 is updated with Mauna Loa’s latest measurements of atmospheric CO2 and with the Energy Information Administration’s new estimates of global CO2 emissions. by 2050. The model shows that atmospheric CO2 will almost double pre-industrial levels by 2100, with the total radiative force of the climate system much lower than the worst-case scenario (RCP8. 5) used in alarm documentation (and the US national climate assessment), with closest conformance to RCP4.5. The model also clearly shows CO2 decrease effects of the 1991 eruption of Mount Pinatubo.
You are conflicted
As described here, the simple CO2 budget model uses annual sources and atmospheric CO2 to calculate how much atmospheric CO2 concentrations change from year to year.
The sinking (removal) of “excess” CO2 from the atmosphere assumes that all biological and geophysical processes that remove CO2 from the atmosphere do so at a real rate proportional to the excess CO2. some ‘equilibrium’ value. When the model was calibrated with annual Mauna Loa CO2 data from 1959 to 2021, this removal rate was 2.02% of the excess in the atmosphere above 294 ppm. So, for example, at the current CO2 concentration of 417 ppm, biological and geophysical removals are removing 0.0202 x [417 – 294] = 2.48 ppm per year for 2022 (rough estimate).
The source of the long-term increase in CO2 is believed to be man-made. There are various estimates of annual CO2 emissions, some from energy use, some including cement production and land use. I used Boden et al. (2017) and Our World in Data estimate annually from 1750 to 2009, and EIA.gov estimates the annual growth rate of emissions from 2010 to 2050, then assuming a constant 2050 growth rate to 2100.
I have also included an ENSO term (El Nino and La Nina) for the empirical calculation of the amount of CO2 increase during El Nino and decrease during La Nina. This term is up to 0.45 times the Multivariable Enso Index (MEI) value averaged from May of the previous year to April of the current year. For example, the most recent mean annual MEI is -1.29 (La Nina condition), so 0.45 x [-1.29] = Â -0.58 ppm CO2 reduction in 2022 from La Nina operation.Â
The model was initialized in 1750. MEI data were included starting from 1958-59.
Result
The model’s fit to the Mauna Loa CO2 data is shown in Figure 1. Note that the largest difference between the model and the observations is due to major volcanic eruptions, especially Mount Pinatubo in 2015. 1991.
Figure 1. Model compared to observed CO2 concentrations at Mauna Loa, HI.
Contrary to popular belief, these eruptions actually remove CO2 from the atmosphere. This may be due to increased photosynthesis due to large increase in diffuse solar radiation from the sky, from sunlight scattered by volcanic aerosols, can penetrate deeper into the plant canopy.
When we run the 2021 usage model EIA estimate Annual CO2 emissions increase from 2010 to 2050, and then assuming the 2050 increase remains the same through 2100, the resulting atmospheric CO2 scenario is closest to the IPCC RCP4.5 scenario. The CO2 concentration in the model barely reaches the 2XCO2 level, which is more than double the pre-industrial CO2 level.
Note that this model is much lower than the RCP8.5 scenario, which is the most commonly used scenario to drive alarmist forecasts for sea level rise, temperature rise, etc.
Discussion
Climate model projections depend heavily on how much CO2 in the atmosphere will increase in the future. That, in turn, depends on (1) future anthropogenic emissions, and (2) the natural rate at which “excess” CO2 is removed from the atmosphere.
A simple budget model of atmospheric CO2 concentrations that matches very well the Mauna Loa CO2 data for 1959-2021 using annual estimates of global anthropogenic CO2 emissions as a source of CO2 and the observed average rate of CO2 removal by biological and physical processes, proportional to the “excess” of atmospheric CO2 above baseline is 295 ppm. An empirical factor to account for El Nino and La Nina activity is also included.
The resulting model projection produces atmospheric CO2 concentrations by the end of this century much lower than the IPCC RCP8.5 scenario and even lower than the RCP6.0 scenario. This suggests that the most severe effects of climate change that the public hears about will not occur. Note that this ability to reduce future global warming impacts is in addition to evidence that the climate system is not as sensitive to CO2 increases as claimed by the IPCC. In other words, future climate change is likely to be much weaker than expected not only due to (1) lower sensitivity to climate, but also (2) weaker anthropogenic impacts. , and the combination of these two factors determines the outcome.
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