Doug L. Hoffman
The Resiliant Earth
Thursday, December 10, 2009

Recent claims by climate change alarmists have raised the possibility that terrestrial ecosystems and particularly the oceans have started loosing part of their ability to absorb a large proportion of man-made CO2 emissions. This is an important claim, because currently only about 40% of anthropogenic emissions stay in the atmosphere, the rest is sequestered by a number of processes on land and sea. The warning that the oceans have reached their fill and their capacity to remove atmospheric CO2 is accompanied by the prediction that this will cause greenhouse warming to accelerate in the future. A new study re-examines the available atmospheric CO2 and emissions data and concludes that the portion of CO2 absorbed by the oceans has remained constant since 1850.

Wolfgang Knorr from the Department of Earth Sciences, University of Bristol, has published a study in Geophysical Research Letters entitled “Is the airborne fraction of anthropogenic CO2 emissions increasing?” Knorr combines data from ice cores, direct atmospheric measurements, and emission inventories to show that the fraction of human emitted CO2 that remains in the atmosphere has stayed constant over the past 160 years, at least within the limits of measurement uncertainty. Here is the paper’s abstract:

Several recent studies have highlighted the possibility that the oceans and terrestrial ecosystems have started loosing part of their ability to sequester a large proportion of the anthropogenic CO2 emissions. This is an important claim, because so far only about 40% of those emissions have stayed in the atmosphere, which has prevented additional climate change. 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. The analysis further shows that the statistical model of a constant airborne fraction agrees best with the available data if emissions from land use change are scaled down to 82% or less of their original estimates. Despite the predictions of coupled climate-carbon cycle models, no trend in the airborne fraction can be found.


This work directly contradicts studies that claim to have shown that the uptake of atmospheric CO2 by the ocean has already slowed. Knorr’s work is backed up by a study in Nature by S. Khatiwala et al.: “Reconstruction of the history of anthropogenic CO2 concentrations in the ocean .” Noting that buring fossil fuels has increased the level of to CO2 in the atmosphere, the authors state “the ocean plays a crucial role in mitigating the effects of this perturbation to the climate system, sequestering 20 to 35 per cent of anthropogenic CO2 emissions.” They found that sequestration by the oceans had not diminished significantly and that land plants have greatly increased their absorption of the gas. Quoting from the paper:



Our results indicate that ocean uptake of anthropogenic CO2 has increased sharply since the 1950s, with a small decline in the rate of increase in the last few decades. We estimate the inventory and uptake rate of anthropogenic CO2 in 2008 at 140 ± 25 Pg C and 2.3 ± 0.6 Pg C yr-1, respectively. We find that the Southern Ocean is the primary conduit by which this CO2 enters the ocean (contributing over 40 per cent of the anthropogenic CO2 inventory in the ocean in 2008). Our results also suggest that the terrestrial biosphere was a source of CO2 until the 1940s, subsequently turning into a sink. Taken over the entire industrial period, and accounting for uncertainties, we estimate that the terrestrial biosphere has been anywhere from neutral to a net source of CO2, contributing up to half as much CO2 as has been taken up by the ocean over the same period.


Some have suggested that reducing human CO2 emissions by 50% would bring atmospheric levels into equilibrium. This new report raises the possibility that, if human emissions were lowered, absorption levels by the oceans and land plants might decline as well, maintaining the growth in overall atmospheric CO2 levels. It also seems possible that, if man’s release of carbon dioxide is greatly reduced, the terrestrial biosphere could shift from a net absorber to a producer of greenhouse gas. The change in sources and sinks over time is presented graphically in figure S3 from the paper’s supplementary information, shown below:





Figure S3: Evolution of anthropogenic CO2 sources and sinks between 1765 and 2005. Sources, shown as positive values, include fossil fuel burning (with a small contribution from cement production) and changes in land use. Sinks are shown as negative values, and include the atmosphere, ocean, and land biosphere. Error envelope, indicated by broken lines and the shaded area, includes estimated uncertainties in the source terms (5% for fossil fuel emissions, and ±0.5 PgC/y for land-use change).


These observations imply that all the hoopla about reining in CO2 levels may be working at odds with nature, that Earth’s environment already has mechanisms in place to regulate changing levels of greenhouse gases. The observation that the terrestrial biosphere was a source of CO2 until the 1940s, and has subsequently become a sink, indicate that the problem is not as simple as shutting down factories and banning SUVs. With nature regulating GHG levels on its own, perhaps we have time to look more closely into the matter before we leap off an economic cliff at the urging of the IPCC and the likes of Al Gore.

Ocean Acidification Reconsidered

Many climate scientists and ecologists seem to seek the dark cloud instead of the silver lining for any new discovery. A case in point is concern over increased ocean acidification due to the absorption of greater amounts of CO2 from the atmosphere. While the previous panic over bleached coral reefs seems to have abated (see “Bleached Coral Reefs Bounce Back”), researchers continue to warn that many species of invertebrates will disappear as the oceans acidify. But new observations indicate that the effects of increased CO2 on marine environments will be more complex than previously predicted. In fact, a new study shows that some of these species may benefit from ocean acidification, growing bigger shells or skeletons that provide more protection.

Because different ocean creatures use different forms of calcium carbonate for their shells, marine scientist Justin Ries of the University of North Carolina at Chapel Hill, hypothesized that not all ocean organisms would respond the same way to increased acidity. Ries and two colleagues from the Woods Hole Oceanographic Institution, Anne L. Cohen and Daniel C. McCorkle, exposed marine organisms from 18 marine species to four levels of seawater acidity. As described in an article from ScienceNOW, the first environment matched today’s atmospheric CO2 levels. The second and third were set at double and triple the pre-Industrial CO2 levels, conditions the IPCC has predicted to occur over the next century. The fourth CO2 level was 10 times pre-Industrial levels, a level not seen since before the onset of the Pleistocene Ice Age more than 3 million years ago.





Exposure to today’s atmospheric CO2 levels (400 ppm, left), and 10 times the pre-Industrial level (2850 ppm, right) resulted in American lobster and blue crabs with unexpectedly larger, heavier exoskeletons. Credit: J. Ries.


Blue crabs, lobsters, and shrimp thrived in the highest CO2 level, growing heavier shells, the researchers reporte in Geology. Ries speculates that these bottom dwellers are somehow better able to manipulate CO2 ions to build their shells, even though fewer ions are available to them in an acidic environment. Exactly how they accomplish this remains unknown. Meanwhile, American oysters, scallops, temperate corals, and tube worms all fared poorly, growing thinner, weaker shells. Clams and pencil urchins, who’s exoskeletons dissolved at the highest CO2 levels, were the biggest potential losers. In all a thought provoking study, but we don’t need to borrow trouble.

Barring any massive natural outgassing of greenhouse gas, CO2 levels will not rise as high as those in the fourth test environment, at least not in the foreseeable future. The atmosphere did experience similar CO2 levels during the middle of the Cretaceous period about 100 million years ago. “This is an interval in which many of these organisms lived and apparently did okay, despite the extremely elevated levels of atmospheric CO2 that existed at that time,” Ries said. “The take-home message is that the responses to ocean acidification are going to be a lot more nuanced and complex than we thought.” As usual when Earth’s climate changes, there are winners and losers but life carries on.

For Earth to experience such conditions the Pleistocene Ice Age must come to an end, which implies the melting of all significant glaciers, a tremendous rise in sea levels and other climatic changes scientists can only guess at. On the bright side, if Earth is transitioning back to pre-ice age conditions mankind really doesn’t have any say in the matter—at least our conscience will be clear.

That High Temperature Record

As a final note, it has become fashionable to declare current global temperatures as the highest in more than a million years, implying that anthropogenic global warming has resulted in a climate that is out of the norm for interglacials during the Pleistocene Ice Age. An article in the November 19, 2009, edition of Nature by David Noone has revealed that, using temperature estimates derived from isotopes in polar ice cores, interglacial periods were rather warmer than previously thought. How much higher is hard to say exactly given the limits of measurement accuracy for the proxy data but “the last warm period, the Eemian, occurred around 128,000 years ago, and from various proxy measurements it is widely accepted that temperatures then were higher than those during modern pre-industrial times.”

According to the USGS, during the peak of the last interglacial period, around 125 thousand years ago, sea level was about 6 m (20 ft) higher than present. This estimate is based on dating of emergent coral reefs on tectonically stable coastlines distant from plate boundaries. These data indicate that global ice volumes were significantly lower than present, by an amount equivalent to the present volume of the Greenland or West Antarctic ice sheets. This in turn suggests that temperatures were higher for longer than today in order to melt that volume of ice—all without human help. Despite these findings, global warming alarmists continue to issue bombastic statements that are known to be false—what kind of scientists are these people, who purposely mislead the public?

Be safe, enjoy the interglacial and stay skeptical.



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