SOIL CARBON AND CLIMATE CHANGE
NEWS
From
Consortium for Agricultural
Soils Mitigation of Greenhouse Gases(CASMGS)
http://soilcarboncenter.k-state.edu
Charles W. Rice, K-State
Department of Agronomy, National CASMGS Director
(785) 532-7217 cwrice@ksu.edu
Scott Staggenborg, K-State Department
of Agronomy (785) 532-7214 sstaggen@ksu.edu
Steve Watson, CASMGS
Communications (785) 532-7105 swatson@ksu.edu
June 30, 2006
No. 48
Science:
* Greenhouse Gas Levels Continue To Rise In 2005
* Do Plants Produce Methane? Analysis Of The Research
National:
*
**********
Greenhouse
Gas Levels
Continue
To Rise In 2005
The US National Oceanic and Atmospheric Administration (NOAA)
reported on May 1, 2006 that carbon dioxide levels increased from 2004 to 2005,
according to the agency's Annual Greenhouse Gas Index, or AGGI. Nitrous oxide
levels also rose, but methane and chlorofluorocarbon levels decreased. The AGGI
showed a 1.25 percent rise in overall greenhouse gases in 2005. The AGGI stood
at 1.215 in 2005 compared to the 1990 baseline value of 1.00, showing a steady
rise in greenhouse gases over the past 15 years. Global levels of carbon
dioxide increased from an average of 376.8 parts per million in 2004 to 378.9
parts per million in 2005. The report can be found at: www.cmdl.noaa.gov/aggi
Global averages of the concentrations of the major,
well-mixed, long-lived greenhouse gases, carbon dioxide, methane, nitrous
oxide, CFC-12 and CFC-11 from the NOAA global flask sampling network since
1978. These gases account for about 97% of the direct radiative forcing by
long-lived greenhouse gases since 1750.
-- Steve Watson swatson@ksu.edu
**********
Do
Plants Produce Methane?
Analysis
Of The Research
A recent study, led by Frank Keppler from the Max Planck
Institute, found that plants emit significant amounts of methane, a potent
greenhouse gas. Does this research call into question the value of carbon
sequestration from trees and plants as a climate change mitigation strategy, or
is this speculation as overblown? What did the research really say? What do
scientific experts think about its significance? In response to the publication
of these papers and the confusion and questions they and the press surrounding
them generated, the Nicholas Institute for Environmental Policy Solutions at
Excerpts from the document follow:
Two recent papers in the scientific literature have
generated speculation regarding the benefits of terrestrial carbon sinks. One
paper, led by Frank Keppler from the Max Planck Institute found that plants
emit significant amounts of methane, a potent greenhouse gas. (Another study,
led by Robert Jackson of
In the Nature paper, Frank Keppler and his coauthors report on a previously unmeasured source of methane emissions - living plants and their fallen leaves. Methane is a potent greenhouse gas, with a warming potential 23 times greater than carbon dioxide. At first glance, Keppler’s paper suggests the need to reassess the value of biological carbon sinks. If living plants are emitting methane, the benefit gained by planting or replanting forests to sequester carbon could be countered by the release of methane from the trees.
1. What did this new research by Keppler et al. say?
In their research, Keppler and his team measured methane emitted from plants and leaves in a laboratory. The discovery of this previously undetected source of methane and an unknown mechanism for methane production was met with some surprise and significant interest among the scientific community. The authors’ admittedly rough estimate of how much of the annual global methane emissions could come from this previously unmeasured source, 10-30%, was surprisingly large and generated much of the concern and confusion surrounding the publication of the article.
A crucial underlying fact about this research that was mischaracterized in some of the press coverage is that this source of methane is not a new phenomenon. However, scientists had never identified it, distinguished it from other sources, or included it as an identified source in global methane budgets. Although existing uncertainty in the budget provides room for an unidentified source, that this previously undetected plant-produced source could be as large as calculated by the authors gave rise to skepticism among some scientists. Balancing the sinks and sources of methane, with Keppler et al.’s estimates, would have required that other sources of methane have been overestimated.
Keppler and his coauthors were the first to detect methane emission from a wide variety of plants and their fallen leaves. They were the first to try to quantify this flux from plants and the first to try to understand this new mechanism of methane production. Scientific discovery is an iterative process. While they have taken the very first step and discovered a new phenomenon, much research still needs to be done before we will know enough to incorporate this new methane flux into greenhouse gas mitigation planning and accounting.
While Keppler and his coauthors used their laboratory findings to calculate global methane estimates from plants and found these estimates to be fairly large, they did not suggest major policy implications for their results. In contrast, the science news and general press made broad generalizations, often in the headlines, which led to a misinterpretation of the research suggesting that the benefit of forests for carbon storage could be substantially reduced based on the results of this study. The authors themselves felt this was a misinterpretation of their results and replied with a press release from the Max Plank Institute clarifying their results.
The preliminary extrapolation done in the research paper estimated that methane emitted from plants could make up 10 to 30% of the total methane emitted annually from all sources. The press suggested that this would greatly diminish or eliminate the climate benefits of forestry from sequestration. This inference, however, is incorrect. What Keppler and his coauthors report is a large flux of methane, but still it would only slightly diminish the carbon sequestration benefit of a forestry project, if it would do so at all. In the clarifying press release from the authors, they state: "... the climate benefits gained through carbon sequestration by reforestation far exceed the relatively small negative effect, which may reduce the carbon uptake effect by up to 4%.”
While the participants accepted that plant methane emissions were likely measured by Keppler and his coauthors, there was a general sense that these results should be replicated and validated through further experimentation.
Other recent scientific research may lend some support to Keppler’s findings of methane production from plants. A number of measurements in the Amazon suggest that the concentration of methane that accumulates in the forest canopy and the atmosphere above the Amazon region is too high to be easily explained by the sources usually considered. These studies may provide support for Keppler’s observations of methane emissions from plants, but are not detailed enough to help quantify them. Participants in this discussion also noted that Keppler showed no consistent differences in methane emissions from different kinds of plants. Measured methane emissions from grasses and trees were variable and overlapping.
2. Should the emission of methane by plants, as described in Keppler’s paper, change current or proposed policies for land use projects designed for the sequestration of carbon?
The answer is no. Keppler’s paper does not add a new methane source; rather it better defines what is in the uncertainty of current global measurements. The reduction in sequestration benefits from methane emissions from plants may be in the range of 0.4%, based on our discussion, or 4% based on the authors’ original calculation. In either case, it would likely make little difference in current policy design and, based on the precision in accounting methods it would likely have little significance for individual projects.
Furthermore, in most terrestrial sequestration projects,
trees replace grasses, shrubs, or crops. In Keppler’s study they show no clear
difference between the emissions from grasses and those from trees. There is no
indication that a plantation would emit more methane than the grassland or
other land cover that it replaces. With the development of a carbon market
under the Kyoto Protocol (KP) and the potential of a carbon market or carbon
policies in non-Kyoto countries like the
In summary:
* Plants appear to be a previously undetected source of methane. Using the estimates in the published study, the methane produced by a forest would reduce the carbon sequestration climate benefits by about 4%.
* The group gathered at Duke suggested refinements to the global estimate that would reduce the methane flux by a factor of 10. If future research finds this reduced estimate to be closer to the actual flux, the methane produced by plants would be only a small fraction of the global methane budget.
* More importantly, it is likely that no change in the sequestration climate benefit will be observed. The measurements in the study could not distinguish if the magnitude of methane emissions from trees is any different from that of grasses. Thus, we do not know whether replacing grasslands with forests will increase, decrease, or have no net effect on methane emissions.
* Irrespective of whether the original estimated fluxes are used or those suggested by this consensus group, the impacts on carbon sequestration benefits of forests are quite small. Methodologies typically used to assess the greenhouse gas benefits of carbon sequestration are sufficiently comprehensive and sophisticated to incorporate the impacts of methane emissions.
The
report can be found at: www.env.duke.edu/institute/methanewater.pdf
-- Steve Watson swatson@ksu.edu
**********
Record
Trading Month In May
Chicago Climate Exchange (CCX) announced that the total trading volume of CCX Carbon Financial Instrument contracts in May was 2,435,400 metric tons carbon dioxide. This doubles the total April 2006 volume of 1,069,400 metric tons of CO2 making it the highest monthly trading volume to date and the first month to break the mark of two million tons traded.
Total trading volume in the first half of May also surpassed the total trading volumes for 2004 and 2005. The highest single day trading volume record for CCX was set on May 15, 2006 when 698,000 metric tons traded, surpassing the previous record established on May 11, 2006 of 561,900 metric tons.
Trading during May occurred in all vintages from 2003 through 2010. (See May 15, 2006 CCX Market Summary below). Cumulative trading volume since December 2003 is 8,480,000 metric tons of CO2.
Market Summary
– May 1 to May 15, 2006
CCX Carbon
Financial Instrument™ contracts (CFI™)
|
High |
Low |
Last |
Volume (metric tons) |
||
|
2003 |
$3.85 |
$2.95 |
$3.70 |
106,000 |
|
|
2004 |
$3.85 |
$3.00 |
$3.70 |
118,500 |
|
|
2005 |
$3.85 |
$3.00 |
$3.65 |
108,700 |
|
|
2006 |
$3.85 |
$3.00 |
$3.65 |
60,800 |
|
|
2007 |
$3.75 |
$3.00 |
$3.60 |
504,700 |
|
|
2008 |
$3.75 |
$3.00 |
$3.55 |
545,200 |
|
|
2009 |
$3.75 |
$3.10 |
$3.55 |
502,800 |
|
|
2010 |
$3.75 |
$3.10 |
$3.55 |
488,700 |
|
|
2,435,400 |
|||||
Price Units: Per metric ton of CO2
Volume Units: metric tons CO2
For details, see www.chicagoclimateexchange.com
-- Rafael Marques,
rmarques@chicagoclimateexchange.
**********
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