A couple of months back, there was a discussion taking place over at Joe Romm’s ClimateProgress blog concerning a report that the earth’s ability to take-up atmospheric carbon dioxide was declining. A declining CO2 sink, of course, meant that things climatological were going to be even worse than expected, because a growing proportion of anthropogenic CO2 emissions were going to remain in the atmosphere, thus pushing the rise of CO2 concentrations and the degree of climate change higher.
At the time, an alert reader pointed out to Joe Romm that there was in fact, no indication from data and observations that a larger percentage of human CO2 emissions were ending up in the atmosphere. In fact, the data showed that the fraction of CO2 emitted into the atmospheric by human activities has remained constant for the past 40 years.
This fact runs directly counter to the idea that the earth’s natural CO2 sinks are weakening—instead it indicates that natural sinks have been expanding as anthropogenic CO2 emissions have increased. After all, in order to keep the airborne fraction of CO2 emissions constant over time, increasing anthropogenic CO2 emissions must be countered by an increasing CO2 sink.
Joe Romm was a bit dismissive (to say the least) of this line of argument.
Here was one such exchange (Comment 13 of this thread):
Comment 13. Chip Knappenberger says:
March 30, 2009 at 5:15pm
I am not sure how you justify this statement:
“At the same time that CO2 emissions are soaring, CO2 sinks are saturating.”
Take your numbers for the rate of CO2 increase each year and divide them by the numbers for the annual global CO2 emissions each year (available from the Carbon Dioxide Information Analysis Center, http://cdiac.ornl.gov/ ftp/ ndp030/ global.1751_2005.ems) and see what you get.
Hint: the ppm/emissions ratio shows no trend at all which means that there is no decline in the CO2 sink—otherwise, this ratio would be increasing.
[JR: It is Dr. Romm, Chip, and, hint, it is what the scientific literature says. Try reading it, some time. Start with the Global Carbon Project.]
Just in case JR (Dr. Romm) really is interested in what the latest scientific literature on the topic says, there is a new paper in the journal Geophysical Research Letters that directly examines this issue. The paper is by Wolfgang Knorr a senior researcher in the Department of Earth Sciences at the U. K’s University of Bristol, and is aptly titled with the question “Is the airborne fraction of anthropogenic CO2 emissions increasing?”
Dr. Knorr carefully analyzed the record of anthropogenic CO2 emissions, atmospheric CO2 concentrations, and anthropogenic land-use changes for the past 150 years. Keeping in mind the various sources of potential errors inherent in these data, he developed several different possible solutions to fitting a trend to the airborne fraction of anthropogenic carbon dioxide emissions. In all cases, he found no significant trend (at the 95% significance level) in airborne fraction since 1850. (Note: It is not that the total atmospheric burden of CO2 has not been increasing over time, but that of the total CO2 released into the atmosphere each year by human activities, about 45% remains in the atmosphere while the other 55% is taken up by various natural processes—and these percentages have not changed during the past 150 years)
Controversial new climate change results
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.