Global anthropogenic CO2 emissions have been on a slight downward trend since 2011 – Is it up because of that?
Via Kenneth Richard above 9. December 2021
Until recently, human CO2 emissions were responsible for ~10% of the variance of the annual CO2 growth rate. But a new analysis says human CO2 emissions have fallen slightly over the past decade. So obviously 0% is responsible.
CO2 emissions arising from human activities (fossil fuel burning and land use changes) account for only about +0.1 to 0.3 PgC/year of the annual change in CO2 concentrations. This is about “10% of the variance (σ²) of the rate of CO2 increase” (Wang et al., 2013).
Image source: Wang et al., 2013
Jones and Cox (2005) have shown that changes related to annual fossil fuel emissions are unlikely to explain the CO2 growth rate anomaly.
“… It is unlikely that these anomalies can be explained by a sudden increase in anthropogenic emissions, since the anomaly is much larger than the annual increase in fossil fuel emissions. .”
Image source: Jones and Cox, 2005
Dr. Jari Ahlbeck (2009) also concluded that the correlation between fossil fuel emissions and the increase in the CO2 growth rate is “obviously not statistically significant.” He therefore excluded this factor from consideration in his analysis of the mechanisms of CO2 transformation.
A chart included in the body of the paper shows other 5-year periods of declines in annual trends in CO2 emissions (5.33, 5.17, 5, 13, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5 terms, 5, 5, 5, 13, 5, 5, 17, 5, 17, 5, 5, 13, 5, 5, 13, 5, 13, 5; 11, 5.29 GtC/year for 1980-1984) or a flat trend (6.40, 6.53, 6.63, 6.59, 6.57 GtC/year 1995-1999).
Image source: Ahlbeck, 2009
And now a detailed updated analysis in Carbon Summary The blog suggests “global CO2 emissions have been constant – if not slightly – over the past 10 years.”
Image source: Carbon Summary
In stark contrast to small to non-existent changes in annual anthropogenic CO2 growth rates, there is a large amount of uncertainty and a lack of observational knowledge when estimating large changes. year in natural CO2 emissions from the Earth’s Soil.
While anthropogenic CO2 emissions from fossil fuel combustion and land use change range between 9 and 10 GtC/year with little variance in the 21st century, emissions from land are estimates range from 78 GtC to 108 GtC/year in recent decades (Huang et al., 2021).
This natural CO2 emissions annually is about 8 to 10 times greater than the emissions from all human activities combined (Carey et al., 2016).
The difference in uncertainty ±15 GtC/year (78 to 108 GtC/year) is orders of magnitude larger than the variance of annual growth rates from man-made sources.
Image source: Huang et al., 2021
So we have (a) flat with the trend of decreasing annual anthropogenic CO2 emissions over the past decade, (b) many times smaller annual CO2 emissions from anthropogenic sources relative to nature, and (c) uncertainty about the degree of change relative to nature Sources of CO2 emissions.
So, is there a point where we question the importance of human contributions to overall changes in atmospheric CO2? Or has the perception of “stable science” precluded such an examination?
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