Noting that "throughout the Holocene, northern peatlands have both accumulated carbon and emitted methane," so that "their impact on climate radiative forcing has been the net of cooling (persistent CO2 uptake) and warming (persistent CH4 emission)," Frolking and Roulet (2007) further analyzed this situation by developing Holocene peatland carbon flux trajectories based on estimates of contemporary CH4 flux, total accumulated peat C, and peatland initiation dates, which they used as inputs to a simple atmospheric perturbation model to calculate the net radiative impetus for surface air temperature change. In doing so, the two researchers determined that the impact on the current atmosphere of northern peatland development and carbon cycling through the Holocene is a net deficit of 40-80 Pg CO2-C (~20-40 ppm of atmospheric CO2) and a net excess of ~200-400 Tg CH4 (~75-150 ppb of atmospheric CH4).

In discussing their findings, Frolking and Roulet note that early in the Holocene, the capture of CO2 and emission of CH4 by earth's northern peatlands is likely to have produced a net warming impetus of up to +0.1 W m^-2. Over the following eight to eleven thousand years, however, they say that earth's peatlands have been doing just the opposite, and that the current radiative forcing due to these atmospheric CO2 and CH4 perturbations represents a net cooling force on the order of -0.22 to -0.56 W m^-2. Hence, it can be appreciated that the impetus for global cooling due to carbon sequestration by earth's peatlands historically has been -- and currently is -- significantly greater than the global warming potential produced by their emissions of methane.

In introducing another important paper that deals with a second major aspect of the subject, Turetsky et al. (2007) write that "ongoing climate change has triggered widespread degradation of localized permafrost in peatlands across continental Canada," which observation has led many a climate alarmist to become, well, alarmed ... alarmed that the large volumes of methane being released to the atmosphere by this phenomenon, from both North America and Eurasia, might significantly exacerbate global warming, as suggested by Al Gore in his 21 March 2007 testimony before the United States Senate's Environment & Public Works Committee. Consequently, as Turetsky et al. describe it, they explored "the influence of differing permafrost regimes (bogs with no surface permafrost, localized permafrost features with surface permafrost, and internal lawns representing areas of permafrost degradation) on rates of peat accumulation at the southernmost limit of permafrost in continental Canada." This work revealed, in the words of the five American researchers, that "surface permafrost inhibits peat accumulation and that degradation of surface permafrost stimulates net carbon storage in peatlands." In fact, they report that "unfrozen bogs and internal lawns had net organic matter accumulation rates two-times faster [our italics] than rates of accumulation in localized permafrost features over the most recent 25-year horizon."

In discussing their findings, Turetsky et al. say their data suggest that "permafrost degradation within peatland environments, likely triggered by climate change, could serve as a negative feedback to net radiative forcing via enhanced carbon accumulation as peat." They note, however, that "increased methane emissions to the atmosphere will partially or even completely offset this enhanced peatland carbon sink for at least 70 years following permafrost degradation." Nevertheless, they say that because "internal lawns succeed relatively quickly (within 70 years) to more bog-like conditions and [since] bogs in continental Canada are associated with low methane emissions, the degradation of localized permafrost in peatlands is likely over the long-term to serve as a negative feedback to radiative forcing [our italics]."

Lastly, Fenner et al. (2007) write that "peatland ecosystems are vast global repositories of organic matter, containing an estimated 455 Gt of carbon (Gorham, 1991)," and they suggest, therefore, that it is important to determine how they will likely respond to projected increases in the air's CO2 content. Hence, they collected intact peat monoliths -- comprised predominantly of Sphagnum (S. subnitens Russ. and Warnst.) and Festuca ovina L., with small amounts of Juncus effusus L. and Polytrichum commune Hedw. -- in perfusion systems that allowed for fine control of the water table and lateral water movements, which they maintained for approximately three years in Solardomes with atmospheric CO2 concentrations of ambient or ambient plus 235 ppm, while daily supplying the mini-ecosystems with synthetic rainwater that was comparable in volume and nutrient content to that received at the site from which the monoliths were extracted.

At the end of their 3-year experiment, the seven UK researchers say they found that "species composition showed a shift from a Sphagnum-dominated community to one in which vascular monocotyledonous species dominated," as S. subnitens cover declined by 39% under elevated CO2, whereas J. effusus cover increased, from less than 1% in the control perfusion systems to 40% in the systems exposed to elevated CO2. At the same time, they found that "aboveground plant biomass showed a substantial increase under elevated CO2 (115%, P < 0.01) as did belowground biomass (96%, P < 0.01)." What is more, they report that "J. effusus roots were observed to be particularly thick, deep, and extensive under elevated CO2."

In conclusion, as the air's CO2 content continues to climb ever higher, it would appear that the carbon content of the planet's peatlands should also continue to rise -- and dramatically so -- especially if ecosystem productivity responds like it did in the monoliths studied by Fenner et al. These latter researchers, however, suggest just the opposite; but their reason for doing so derives from their believing in the validity of the tremendous warming that is predicted to accompany the increase in atmospheric CO2 by the world's newest Nobel Peace Prize winner, i.e., the IPCC (and Al Gore). We feel a greater allegiance to sticking with what is more surely known, among which things are the results of Fenner et al.'s own experimentation.

References
Fenner, N., Ostle, N.J., McNamara, N., Sparks, T., Harmens, H., Reynolds, B. and Freeman, C. 2007. Elevated CO2 effects on peatland plant community carbon dynamics and DOC production. Ecosystems 10: 635-647.

Frolking, S. and Roulet, N.T. 2007. Holocene radiative forcing impact of northern peatland carbon accumulation and methane emissions. Global Change Biology 13: 1079-1088.

Gorham, E. 1991. Northern peatlands: role in the carbon cycle and probable responses to climatic warming. Ecological Applications 1: 185-192.

Turetsky, M.R., Wieder, R.K., Vitt, D.H., Evans, R.J. and Scott, K.D. 2007. The disappearance of relict permafrost in boreal North America: Effects on peatland carbon storage and fluxes. Global Change Biology 13: 1922-1934.