Is the airborne fraction of anthropogenic CO2 emissions increasing?

Knorr, W. (2009), Is the airborne fraction of anthropogenic CO2 emissions increasing?, Geophys. Res. Lett., 36, L21710, doi:10.1029/2009GL040613.  (pdf at link below)

Abstract: ….” This study re-examines the available atmospheric CO2 and emissions data including their uncertainties. It is shown that with those uncertainties, the trend in the airborne fraction since 1850 has been 0.7 ±1.4% per decade, i.e. close to and not significantly different from zero.”

“Despite the predictions of coupled climate-carbon cycle models, no trend in the airborne fraction [of CO2] can be found.”

4. Results…. “The most important result is that inclusion of data uncertainties moderately increases the uncertainty of the trend estimate ,s. Furthermore, the use of the inter annual predictors (nN+vV) hardly reduces the uncertainty ins. The trend itself is either very close to zero (Versions 3 and 5), or slightly negative when using interannual predictors (Versions 4 and 6). In none of the cases there is a significant trend.”

…”Without the inclusion of ENSO and VAI in the analysis, the trend derived with data uncertainties is found to be very small, only 0.7 ± 1.4 or 0.2 ± 1.7% per decade, depending on whether the ice core record has been included or not. This is not significantly different from zero and in contrast to the previously published result [Canadell et al.,2007] reporting an increase of 2.5 ± 2.1% per decade, but obtained with de-trended VAI and ENSO index and withoutaccounting for data uncertainties. …”

“Conclusion[25] From what we understand about the underlying processes, uptake of atmospheric CO2should react not to a change in emissions, but to a change in concentrations. A further analysis of the likely contributing processes is necessary in order to establish the reasons for a near-constant AF [airborne fraction of CO2] since the start of industrialization. The hypothesis of a recent or secular trend in the AF cannot be supported on the basis of the available data and its accuracy.”


University of Bristol Press release issued 9 November 2009

New data show that the balance between the airborne and the absorbed fraction of carbon dioxide has stayed approximately constant since 1850, despite emissions of carbon dioxide having risen from about 2 billion tons a year in 1850 to 35 billion tons a year now.

This suggests that terrestrial ecosystems and the oceans have a much greater capacity to absorb CO2 than had been previously expected.

The results run contrary to a significant body of recent research which expects that the capacity of terrestrial ecosystems and the oceans to absorb CO2 should start to diminish as CO2 emissions increase, letting greenhouse gas levels skyrocket. Dr Wolfgang Knorr at the University of Bristol found that in fact the trend in the airborne fraction since 1850 has only been 0.7 ± 1.4% per decade, which is essentially zero.

The strength of the new study, published online in Geophysical Research Letters, is that it rests solely on measurements and statistical data, including historical records extracted from Antarctic ice, and does not rely on computations with complex climate models.

This work is extremely important for climate change policy, because emission targets to be negotiated at the United Nations Climate Change Conference in Copenhagen early next month have been based on projections that have a carbon free sink of already factored in. Some researchers have cautioned against this approach, pointing at evidence that suggests the sink has already started to decrease.

So is this good news for climate negotiations in Copenhagen? “Not necessarily”, says Knorr. “Like all studies of this kind, there are uncertainties in the data, so rather than relying on Nature to provide a free service, soaking up our waste carbon, we need to ascertain why the proportion being absorbed has not changed”.

Another result of the study is that emissions from deforestation might have been overestimated by between 18 and 75 per cent. This would agree with results published last week in Nature Geoscience by a team led by Guido van der Werf from VU University Amsterdam. They re-visited deforestation data and concluded that emissions have been overestimated by at least a factor of two.




Bud Bromley


About budbromley

Bud is a retired life sciences executive. Bud's entrepreneurial leadership exceeded three decades. He was the senior business development, marketing and sales executive at four public corporations, each company a supplier of analytical and life sciences instrumentation, software, consumables and service. Prior to those positions, his 19 year career in Hewlett-Packard Company's Analytical Products Group included worldwide sales and marketing responsibility for Bioscience Products, Global Accounts and the International Olympic Committee, as well as international management assignments based in Japan and Latin America. Bud has visited and worked in more than 65 countries and lived and worked in 3 countries.
This entry was posted in Uncategorized. Bookmark the permalink.

2 Responses to Is the airborne fraction of anthropogenic CO2 emissions increasing?

  1. budbromley says:

    “A key relationship in the theory of anthropogenic global warming (AGW) is that between annual fossil fuel emissions and annual changes in atmospheric CO2. The proposed causation sequence is that annual fossil fuel emissions cause annual changes in atmospheric CO2 which in turn intensifies the atmosphere’s heat trapping property. It is concluded that global warming is due to changes in atmospheric composition attributed to human activity and is therefore a human creation and that therefore we must reduce or eliminate fossil fuel emissions to avoid climate catastrophe (Parmesan, 2003) (Stern, 2007) (IPCC, 2014) (Flannery, 2006) (Allen, 2009) (Gillett, 2013) (Meinshausen, 2009) (Canadell, 2007) (Solomon, 2009) (Stocker, 2013) (Rogelj, 2016). “

    “A testable implication of the proposed causation sequence is that annual changes in atmospheric CO2 must be related to annual fossil fuel emissions at an annual time scale. This work is a test of this hypothesis. We find that detrended correlation analysis of annual emissions and annual changes in atmospheric CO2 does not support the anthropogenic global warming hypothesis because no evidence is found that changes in atmospheric CO2 are related to fossil fuel emissions at an annual time scale. These results are consistent with prior works that found no evidence to relate the rate of warming to the rate of emissions (Munshi, The Correlation between Emissions and Warming in the CET, 2017) (Munshi, Long Term Temperature Trends in Daily Station Data: Australia, 2017) (Munshi, Generational Fossil Fuel Emissions and Generational Warming: A Note, 2016) (Munshi, Decadal Fossil Fuel Emissions and Decadal Warming: A Note, 2015) (Munshi, Effective Sample Size of the Cumulative Values of a Time Series, 2016) (Munshi, The Spuriousness of Correlations between Cumulative Values, 2016.)”

    “The finding raises important questions about the validity of the IPCC carbon budget which apparently overcomes a great uncertainty in much larger natural flows to describe with great precision how flows of annual emissions are distributed to gains in atmospheric and oceanic carbon dioxide (Bopp, 2002) (Chen, 2000) (Davis, 2010) (IPCC, 2014) (McGuire, 2001). These carbon budget conclusions are inconsistent with the findings of this study and are the likely result of insufficient attention to uncertainty, excessive reliance on climate models, and the use of “net flows”
    (Plattner, 2002) that are likely to be subject to assumptions and circular reasoning (Edwards, 1999) (Ito, 2005) (Munshi, 2015a) (Munshi, 2016) (Munshi, An Empirical Study of Fossil Fuel Emissions and Ocean Acidification, 2015).”


Leave a Reply

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.