The talk with present the key results of the IPCC Working Group III 5th assessment report. Concluding four years of intense scientific collaboration by hundreds of authors from around the world, the report responds to the request of the world's governments for a comprehensive, objective and policy neutral assessment of the current scientific knowledge on mitigating climate change. The report has been extensively reviewed by experts and governments to ensure quality and comprehensiveness.

Climate change 2014 - Mitigation of climate change

Soil microorganisms as controllers of atmospheric trace gases (H2, CO, CH4, OCS, N2O, and NO).

A positive temperature coefficient is the term which has been used to indicate that an increase in solubility occurs as the temperature is raised, whereas a negative coefficient indicates a decrease in solubility with rise in temperature.

Effect of Temperature

Stable isotopes in tree rings.

/pdf/remote-sensing-of-the-environment-4yfxjaaswe.pdf

Remote sensing of the environment

[i] Peatlands represent an important component of the global carbon cycle, storing 23 g C m -2 yr -1 . Peatland mining eliminates the carbon sink function of the peatland. In this paper we measure the total ecosystem respiration in a natural, 2 and 3 year (young) and 7 and 8 year (old) postcutover peatland near Sainte-Marguerite-Marie, Quebec, during the summers of 1998 and 1999. Although the natural site was a source of CO 2 during the dry 1998 study season (138 g C m -2 ), CO 2 emissions were between 260 and 290% higher in the cutover sites (363 and 399 g C m -2 for young and old, respectively). Cutover site CO 2 emissions were only 88 and 112 g CO 2 .C m -2 at the young and old sites during the wet 1999 study season. Total ecosystem respiration was more dependent on the water table position than on changes in the thermal regime or the labile carbon of the peat in a dry summer, but the opposite was the case in a wet summer. CO 2 emissions increased with postharvest time regardless of a decrease in labile carbon, demonstrating that cutover peatlands are a large persistent source of atmospheric CO 2 . Direct measurement of the net ecosystem CO 2 exchange in cutover peatlands, as opposed to determining the loss of carbon from bulk density determinations, provides a better understanding of how peat drainage and harvesting operations affect the carbon balance in peatlands.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2001GB001398

Cutover peatlands: A persistent source of atmospheric CO2

Northern peatlands play an important role globally in the cycling of C, through the exchange of CO2 with the atmosphere, the emission of CH4, the production and export of dissolved organic carbon (DOC) and the storage of C. Under 2 × CO2 GCM scenarios, most Canadian peatlands will be exposed to increases in mean annual temperature ranging between 2 and 6° C and increases in mean annual precipitation of 0 to 15 %, with the most pronounced changes occurring during the winter. The increase in CO2 uptake by plants, through warmer temperatures and elevated atmospheric CO2, is likely to be offset by increased soil respiration rates in response to warmer soils and lowered water tables. CH4 emissions are likely to decrease in most peatlands because of lowered water tables, except where the peat surface adjusts to fluctuating water tables, and in permafrost, where the collapse of dry plateau and palsa will lead to increase CH4 emission. There likely will be little change in DOC production, but DOC export to water bodies will decrease as runoff decreases. The storage of C in peatlands is sensitive to all C cycle components and is difficult to predict. The challenge is to develop quantitative models capable of making these predictions for different peatlands. We present some qualitative responses, with levels of uncertainty. There will be, however, as much variation in response to climatic change within a peatland as there will be among peatland regions.

Uncertainty in Predicting the Effect of Climatic Change on the Carbon Cycling of Canadian Peatlands

Northern peatlands provide important global and regional ecosystem services (carbon storage, water storage, and biodiversity). However, these ecosystems face increases in the severity, areal extent and frequency of climate-mediated (e.g. wildfire and drought) and land-use change (e.g. drainage, flooding and mining) disturbances that are placing the future security of these critical ecosystem services in doubt. Here, we provide the first detailed synthesis of autogenic hydrological feedbacks that operate within northern peatlands to regulate their response to changes in seasonal water deficit and varying disturbances. We review, synthesize and critique the current process-based understanding and qualitatively assess the relative strengths of these feedbacks for different peatland types within different climate regions. We suggest that understanding the role of hydrological feedbacks in regulating changes in precipitation and temperature are essential for understanding the resistance, resilience and vulnerability of northern peatlands to a changing climate. Finally, we propose that these hydrological feedbacks also represent the foundation of developing an ecohydrological understanding of coupled hydrological, biogeochemical and ecological feedbacks. Copyright © 2014 John Wiley & Sons, Ltd.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/eco.1493

Hydrological feedbacks in northern peatlands

Measurement of the spatial variability of CH4 emissions and net CO2 ecosystem exchange were made in a boreal peatland in northern Sweden in the summers of 1992 and 1993. Variability was monitored at the microscale (hummocks and hollows), mesoscale (ridges, lawns and pools), and macroscale (landforms) to assess the role of peatland topography on the magnitude and variability of the fluxes. The general trend is for topographically lower areas, such as hollows, pools, or peatland margins, to have higher CH4 emissions and lower CO2 uptake than the adjacent topographically higher areas such as hummocks, ridges, and plateaus. However, the greatest difference occurs at the microtopographic scale because the maximum differences in water table position and temperature occur at the microscale. The CH4 flux at the margins of the peatland was three to four times greater than that observed at the central plateau sites. Net CO2 uptake was also greatest at the margin sites. A combined meso-macro topographic model (MMF) was used to estimate the total peatland CH4 and CO2 exchange. The model indicates that a failure to measure the exchange of carbon from peatland pools can result in a large overestimate of the total peatland NEE and therefore carbon accumulation rates.

James M. Waddington

Papers

Cutover peatlands: A persistent source of atmospheric CO2

Uncertainty in Predicting the Effect of Climatic Change on the Carbon Cycling of Canadian Peatlands

Hydrological feedbacks in northern peatlands

Atmosphere-wetland carbon exchanges: Scale dependency of CO2 and CH4 exchange on the developmental topography of a peatland

Carbon balance of a boreal patterned peatland