A couple of days ago we received a Physorg.com article via Alan Siddons, Even soil feels the heat: Soils release more carbon dioxide as globe warms
], this was a summary article for a report that appeared in Nature (Bond-Lamberty and Thomson, 2010. Temperature-associated increases in the global soil respiration record, Nature March 25, 2009
Alan included the following comments.
More evidence that a climbing CO2 rate is the result of warming, not the cause. There are two other ramifications as I see it.
1. Results like this mean that the anthropogenic fraction must be readjusted. Is man's annual contribution 4%? 3%? Less?
2. This latest natural emission estimate shows that previous source/sink models have been inadequate, as usual.
The following then appeared in the comments section of CR
by Ben Bond-Lamberty and Allison Thompson, the authors of the said article.
Updated below from Western Institute for Study of the Environment Commentary
Hi, this is Ben Bond-Lamberty and Allison Thomson, the authors of the Nature article being discussed here. We'd like to note that this commentary by "AS" is incorrect:
• Our paper has nothing to do with whether CO2 is a result or cause of warming.
• This result does not necessarily mean that the anthropogenic fraction must be readjusted. We found that the soil-to-air component of the global carbon cycle is accelerating; this might not, by itself, have any effect on atmospheric CO2 levels. Even if it did, the projected CO2 increase from the soils (0.1 Pg/yr) is around 1% of fossil fuel emissions (8 Pg/yr).
• Our findings don't show that "source/sink models" are inadequate. The acceleration we report has been widely predicted, and seems to be occurring at levels consistent with those assumed by global climate models.
Sincerely, Ben and Allison
Claim: Our paper has nothing to do with whether CO2 is a result or cause of warming.
Yet the article states,
"There's a big pulse of carbon dioxide coming off of the surface of the soil everywhere in the world," said ecologist Ben Bond-Lamberty of the Department of Energy's Pacific Northwest National Laboratory. "We weren't sure if we'd be able to measure it going into this analysis, but we did find a response to temperature."
As I read that, the CO2 being emitted is a result of warming. Moreover, the very next paragraph deals with whether this extra carbon will enhance the greenhouse effect, concluding yes, if the carbon is old. As I read that, the CO2 being emitted is also a possible cause of warming ~ there’s not even a maybe about it if the carbon is old.
Claim: This result does not necessarily mean that the anthropogenic fraction must be readjusted.
From the article again:
"The scientists also calculated the total amount of carbon dioxide flowing from soils, which is about 10-15 percent higher than previous measurements. That number [is] about 98 petagrams of carbon a year (or 98 billion metric tons)
So let’s look at the difference. If 98 billion metric tons (i.e., 98 gigatons) per year is "10-15 percent higher than previous measurements," this indicates that the previous figure was in the neighborhood of 87 gigatons. That's a difference of 11 gigatons of carbon per year, more carbon than man is estimated to emit annually. Consider too that earlier IPCC estimates
put the anthropogenic fraction at 4.5% of the annual global total. Later estimates drew that down to 2.9%. Where it stops nobody knows.
On the other hand, since a 0.1 gigaton increase per year between 1989 and 2008 doesn't square with a 10-15% total increase, perhaps the article is in error and the authors were misquoted.
Claim: Our findings don't show that "source/sink models" are inadequate.
From the Nature introduction itself
Soil respiration, RS, the flux of microbially and plant-respired carbon dioxide (CO2) from the soil surface to the atmosphere, is the second-largest terrestrial carbon flux. However, the dynamics of RS are not well understood and the global flux remains poorly constrained.
I rest my case.
Click Soils, CO2, and Global Warming
to read more from The Western Institute for Study of the Environment Commentary