Climate change and energy - terrestrial emissions

Title

Permafrost carbon-climate feedbacks accelerate global warming

Reference

PNAS September 6, 2011 vol. 108 no. 36 14769-14774

Author(s)

Charles D. Koven , Bruno Ringeval, Pierre Friedlingstein, Philippe Ciais, Patricia Cadule, Dmitry Khvorostyanov, Gerhard Krinner, and Charles Tarnocai

Study type

Peer Review Journal

Abstract

Permafrost soils contain enormous amounts of organic carbon, which could act as a positive feedback to global climate change due to enhanced respiration rates with warming. We have used a terrestrial ecosystem model that includes permafrost carbon dynamics, inhibition of respiration in frozen soil layers, vertical mixing of soil carbon from surface to permafrost layers, and CH₄ emissions from flooded areas, and which better matches new circumpolar inventories of soil carbon stocks, to explore the potential for carbon-climate feedbacks at high latitudes. Contrary to model results for the Intergovernmental Panel on Climate Change Fourth Assessment Report (IPCC AR4), when permafrost processes are included, terrestrial ecosystems north of 60°N could shift from being a sink to a source of CO₂ by the end of the 21st century when forced by a Special Report on Emissions Scenarios (SRES) A2 climate change scenario. Between 1860 and 2100, the model response to combined CO₂ fertilization and climate change changes from a sink of 68 Pg to a 27 + -7 Pg sink to 4 + -18 Pg source, depending on the processes and parameter values used. The integrated change in carbon due to climate change shifts from near zero, which is within the range of previous model estimates, to a climate-induced loss of carbon by ecosystems in the range of 25 + -3 to 85 + -16 Pg C, depending on processes included in the model, with a best estimate of a 62 + -7 Pg C loss. Methane emissions from high-latitude regions are calculated to increase from 34 Tg CH₄/y to 41-70 Tg CH₄/y, with increases due to CO₂ fertilization, permafrost thaw, and warming-induced increased CH₄ flux densities partially offset by a reduction in wetland extent.

Policy theme(s)

Climate change and energy >> Climate change mitigation >> Carbon sinks
Climate change and energy >> Greenhouse gas emissions >> Terrestrial emissions
Soil >> Soil carbon and nitrogen

Keywords

carbon cycle:  land surface models: cryosphere: soil organic: matter active layer

Entry Source:

Selected for Science for Environment Policy News Alert

Referred to in EC doc:

N/A

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http://www.pnas.org/content/108/36/14769.abstract
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cdkoven@lbl.gov

Title

Methane and the greenhouse-gas footprint of natural gas from shale formations.

Reference

Climatic Change, 2011
DOI: 10.1007/s10584-011-0061-5

Author(s)

Robert W. Howarth, Renee Santoro, Anthony Ingraffea.

Study type

Peer Review Journal

Abstract

We evaluate the greenhouse gas footprint of natural gas obtained by highvolume
hydraulic fracturing from shale formations, focusing on methane emissions.
Natural gas is composed largely of methane, and 3.6% to 7.9% of the methane from shale-gas production escapes to the atmosphere in venting and leaks over the lifetime of a well. These methane emissions are at least 30% more than and perhaps more than twice as great as those from conventional gas. The higher emissions from shale gas occur at the time wells are hydraulically fractured-as methane escapes from flow-back return fluids-and during drill out following the fracturing. Methane is a powerful greenhouse gas, with a global warming potential that is far greater than that of carbon dioxide, particularly over the time horizon of the first few decades following emission. Methane contributes substantially to the greenhouse gas footprint of shale gas on shorter time scales, dominating it on a 20-year time horizon. The footprint for shale gas is greater than that for conventional gas or oil when viewed on any time horizon, but particularly so over 20 years. Compared to coal, the footprint of shale gas is at least 20% greater and perhaps more than twice as great on the 20-year horizon and is comparable when compared over 100 years.

Policy theme(s)

Climate change and energy >> Climate change mitigation >> Low carbon and renewable energy
Climate change and energy >> Greenhouse gas emissions >> Terrestrial emissions

Keywords

Methane, Greenhouse gases, Global warming, Natural gas, Shale gas,
Unconventional gas, Fugitive emissions, Lifecycle analysis, LCA, Bridge fuel,
Transitional fuel, Global warming potential, GWP

Entry Source:

Selected for Science for Environment Policy News Alert

Referred to in EC doc:

N/A

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http://www.springerlink.com/content/e384226wr4160653/
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rwh2@cornell.edu

Title

Emissions Embodied in Trade (EET) and Land use in Tropical Forest Margins

Reference

CGIAR policy brief

Author(s)

Minang, P.A., van Noordwijk, M., Meyfroidt, P., Agus, F., Dewi, S.

Study type

Report

Abstract

Increasing proportions of land use change responsible for emissions from deforestation, forest degradation and agriculture in developing countries is associated with commodities meant for export, hence the concept of Emissions Embodied in Trade- EET. As many corporations, countries and consumers embrace carbon footprint labelling and advocate for “greener” commodities, there is potential for reducing emissions from land use change in the humid and sub-humid tropics. Yet, current debate on Reduced Emissions from Deforestation and Degradation - REDD+ has not considered the potential implications of EET. In this brief, we present and briefly reflect on (a) how emission reductions may induce cross-border land use displacements; (b) how market demand for “greener” commodities and consumer pressure on some tropical commodities can shape behaviour of land use agents and influence emissions; and (c) the policy implications that result from EET.

Policy theme(s)

Climate change and energy >> Greenhouse gas emissions >> Terrestrial emissions
Forests >> Forest protection >> Deforestation and degradation
Sustainable development and policy assessment >> Sustainable economic development >> Trade and environment

Keywords

N/A

Entry Source:

Shortlisted for Science for Environment Policy News Alert

Referred to in EC doc:

N/A

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http://www.asb.cgiar.org/PDFwebdocs/PB17_final.pdf
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asb@cgiar.org

Title

Indirect land use change emissions related to EU biofuel consumption: an analysis based on historical data

Reference

Environmental Science & Policy
Volume 14, Issue 3, May 2011, Pages 248-257

Author(s)

Koen P. Overmars, Elke Stehfest, Jan P.M. Ros and Anne Gerdien Prins

Study type

Peer Review Journal

Abstract

Biofuels have recently been promoted in policies as a way to reduce greenhouse gas emissions from the transport sector. However, biofuel production in itself also induces emissions directly as well as indirectly. This paper presents an explicit calculation of indirect land use change (ILUC) emissions from EU biofuel consumption. The approach includes a straightforward methodology for quantifying ILUC, based on assumptions and on data that is readily available. The calculations show that ILUC emissions alone could shift the CO2 balance for biofuels from reductions to more emissions relative to fossil fuels. This calculation is largely based on historical data, which reduces uncertainty compared to forward looking modelling approaches. However, some of the uncertainties remain. Advantage of this approach is that it can easily be reproduced, which may add to the acceptability in the domain of policy making.

Policy theme(s)

Agriculture >> Agricultural management >> Land use change
Climate change and energy >> Climate change mitigation >> Low carbon and renewable energy
Climate change and energy >> Greenhouse gas emissions >> Terrestrial emissions
Land use >> Land use change

Keywords

Indirect land use change (ILUC), Bioenergy, Greenhouse gas emissions, Renewable energy directive

Entry Source:

N/A

Referred to in EC doc:

Shortlisted for Science for Environment Policy News Alert

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http://www.sciencedirect.com/science/article/pii/S1462901110001887
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koen.overmars@pbl.nl

Title

Role of volcanic forcing on future global carbon cycle

Reference

Earth Syst. Dynam., 2, 53-67, 2011

Author(s)

J. F. Tjiputra and O. H. Ottera

Study type

Peer Review Journal

Abstract

Using a fully coupled global climate-carbon cycle model, we assess the potential role of volcanic eruptions on future projection of climate change and its associated carbon cycle feedback. The volcanic-like forcings are applied together with a business-as-usual IPCC-A2 carbon emissions scenario. We show that very large volcanic eruptions similar to Tambora lead to short-term substantial global cooling. However, over a long period, smaller eruptions similar to Pinatubo in amplitude, but set to occur frequently, would have a stronger impact on future climate change. In a scenario where the volcanic external forcings are prescribed with a five-year frequency, the induced cooling immediately lower the global temperature by more than one degree before it returns to the warming trend. Therefore, the climate change is approximately delayed by several decades, and by the end of the 21st century, the warming is still below two degrees when compared to the present day period. Our climate-carbon feedback analysis shows that future volcanic eruptions induce positive feedbacks (i.e., more carbon sink) on both the terrestrial and oceanic carbon cycle. The feedback signal on the ocean is consistently smaller than the terrestrial counterpart and the feedback strength is proportionally related to the frequency of the volcanic eruption events. The cooler climate reduces the terrestrial heterotrophic respiration in the northern high latitude and increases net primary production in the tropics, which contributes to more than 45 % increase in accumulated carbon uptake over land. The increased solubility of CO2 gas in seawater associated with cooler SST is offset by a reduced CO2 partial pressure gradient between the ocean and the atmosphere, which results in small changes in net ocean carbon uptake. Similarly, there is nearly no change in the seawater buffer capacity simulated between the different volcanic scenarios. Our study shows that even in the relatively extreme scenario where large volcanic eruptions occur every five-years period, the induced cooling leads to a reduction of 46 ppmv atmospheric CO2 concentration as compared to the reference projection of 878 ppmv, at the end of the 21st century.

Policy theme(s)

Climate change and energy >> Greenhouse gas emissions >> Terrestrial emissions
Natural hazards >> Geological hazards

Keywords

Volcanoes; carbon cycle

Entry Source:

Shortlisted for Science for Environment Policy News Alert

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N/A

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http://www.earth-syst-dynam.net/2/53/2011/esd-2-53-2011.html
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Jtj061@uib.no

Title

Comparison of soil CO2 flux between uncleared and cleared windthrow areas in Estonia and Latvia

Reference

Forest Ecology and Management
Volume 262, Issue 2, 15 July 2011, Pages 65-70

Author(s)

Kajar Köster, Ülle Püttsepp and Jukka Pumpanen

Study type

Peer Review Journal

Abstract

Storms can turn a great proportion of forests' assimilation capacity into dead organic matter because of windthrow and thus its role as a carbon sink will be diminished for some time. However, little is known about the magnitude or extent to which storms affect carbon efflux. We compared soil CO2 fluxes in wind-thrown forest stands with different time periods since a storm event, and with different management practices (deadwood cleared or left on-site). This study examined changes in soil CO2 efflux in two windthrow areas in north-eastern Estonia and one area in north-western Latvia, which experienced severe wind storms in the summers of 2001, 2002 and 1967, respectively. We measured soil CO2 fluxes in stands formerly dominated by Norway spruce (Picea abies L. Karst.) with total and partial canopy destruction (all trees or roughly half of the trees in stand damaged by storm), in harvested areas (material removed after the wind storm) and in control areas (no damage by wind). Removal of wind-damaged material decreased instantaneous CO2 flux from the soil surface. The highest instantaneous fluxes were measured in areas with total and partial canopy destruction (0.67 g CO2 m-2 h-1 in both cases) compared with fluxes in the control areas (0.51 g CO2 m-2 h-1), in the new storm-damaged areas where the material was removed (0.57 g CO2 m-2 h-1) and in the old storm-damaged area where wood was left on site (0.55 g CO2 m-2 h-1). The only factor affecting soil CO2 flux was location of the measuring collar (plastic collar with diameter 100 mm, height 50 mm) - either on undamaged forest ground or on the uprooted tree pit, where the mineral soil was exposed after disturbance. New wind-thrown stands where residues are left on site would most likely turn to sources of CO2 for several years until forest regeneration reaches to substantial assimilation rates. New wind-thrown stands where residues are left on site would most likely tend to have elevated CO2 fluxes for several years until forest regeneration reaches to substantial assimilation rates. However, forest managers might be concerned about the amounts of CO2 immediately released into the atmosphere if the harvested logs are burned.

Policy theme(s)

Climate change and energy >> Greenhouse gas emissions >> Terrestrial emissions
Forests >> Forest governance and management
Soil >> Soil carbon

Keywords

Soil respiration, Carbon dioxide, Disturbance, Windthrow management

Entry Source:

Shortlisted for Science for Environment Policy News Alert

Referred to in EC doc:

N/A

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http://www.sciencedirect.com/science/article/pii/S0378112710005554
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kajar.koster@emu.ee

Title

Effects of elevated atmospheric CO2, prolonged summer drought and temperature increase on N2O and CH4 fluxes in a temperate heathland

Reference

Soil Biology and Biochemistry
Volume 43, Issue 8, August 2011, Pages 1660-1670

Author(s)

Mette S. Carter, Per Ambus, Kristian R. Albert, Klaus S. Larsen, Michael Andersson, Anders Priemé, Leon van der Linden and Claus Beier

Study type

Peer Review Journal

Abstract

In temperate regions, climate change is predicted to increase annual mean temperature and intensify the duration and frequency of summer droughts, which together with elevated atmospheric carbon dioxide (CO2) concentrations, may affect the exchange of nitrous oxide (N2O) and methane (CH4) between terrestrial ecosystems and the atmosphere. We report results from the CLIMAITE experiment, where the effects of these three climate change parameters were investigated solely and in all combinations in a temperate heathland. Field measurements of N2O and CH4 fluxes took place 1-2 years after the climate change manipulations were initiated. The soil was generally a net sink for atmospheric CH4. Elevated temperature (T) increased the CH4 uptake by on average 10 µg C m-2 h-1, corresponding to a rise in the uptake rate of about 20%. However, during winter elevated CO2 (CO2) reduced the CH4 uptake, which outweighed the positive effect of warming when analyzed across the study period. Emissions of N2O were generally low (<10 µg N m-2 h-1). As single experimental factors, elevated CO2, temperature and summer drought (D) had no major effect on the N2O fluxes, but the combination of CO2 and warming (TCO2) stimulated N2O emission, whereas the N2O emission ceased when CO2 was combined with drought (DCO2). We suggest that these N2O responses are related to increased rhizodeposition under elevated CO2 combined with increased and reduced nitrogen turnover rates caused by warming and drought, respectively. The N2O flux in the multifactor treatment TDCO2 was not different from the ambient control treatment. Overall, our study suggests that in the future, CH4 uptake may increase slightly, while N2O emission will remain unchanged in temperate ecosystems on well-aerated soils. However, we propose that continued exposure to altered climate could potentially change the greenhouse gas flux pattern in the investigated heathland.

Policy theme(s)

Climate change and energy >> Greenhouse gas emissions >> Terrestrial emissions
Soil >> Soil carbon

Keywords

Climate change, Ecosystem manipulation, Greenhouse gas, Methane, Nitrous oxide, Rewetting, Sandy soil, Shrubland, Treatment interaction

Entry Source:

Shortlisted for Science for Environment Policy News Alert

Referred to in EC doc:

N/A

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http://www.sciencedirect.com/science/article/pii/S0038071711001477
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mthy@risoe.dtu.dk

Title

Benchmark map of forest carbon stocks in tropical regions across three continents

Reference

Proceedings of the National Academy of Sciences, 2011;
DOI: 10.1073/pnas.1019576108

Author(s)

Sassan S. Saatchi, Nancy L. Harris, Sandra Brown, Michael Lefsky, Edward T. A. Mitchard, William Salas, Brian R. Zutta, Wolfgang Buermann, Simon L. Lewis, Stephen Hagen, Silvia Petrova, Lee White, Miles Silman, Alexandra Morel.

Study type

Peer Review Journal

Abstract

Developing countries are required to produce robust estimates of forest carbon stocks for successful implementation of climate change mitigation policies related to reducing emissions from deforestation and degradation (REDD). Here we present a 'benchmark' map of biomass carbon stocks over 2.5 billion ha of forests on three continents, encompassing all tropical forests, for the early 2000s, which will be invaluable for REDD assessments at both project and national scales. We mapped the total carbon stock in live biomass (above- and belowground), using a combination of data from 4,079 in situ inventory plots and satellite light detection and ranging (Lidar) samples of forest structure to estimate carbon storage, plus optical and microwave imagery (1-km resolution) to extrapolate over the landscape. The total biomass carbon stock of forests in the study region is estimated to be 247 Gt C, with 193 Gt C stored aboveground and 54 Gt C stored belowground in roots. Forests in Latin America, sub-Saharan Africa, and Southeast Asia accounted for 49%, 25%, and 26% of the total stock, respectively. By analyzing the errors propagated through the estimation process, uncertainty at the pixel level (100 ha) ranged from ±6% to ±53%, but was constrained at the typical project (10,000 ha) and national (>1,000,000 ha) scales at ca. ±5% and ca. ±1%, respectively. The benchmark map illustrates regional patterns and provides methodologically comparable estimates of carbon stocks for 75 developing countries where previous assessments were either poor or incomplete.

Policy theme(s)

Climate change and energy >> Greenhouse gas emissions >> Terrestrial emissions
Forests >> Forest protection >> Deforestation and degradation

Keywords

forest biomass, forest height, microwave and optical imaging, error propagation, carbon cycling

Entry Source:

Shortlisted for Science for Environment Policy News Alert

Referred to in EC doc:

N/A

View this study at:

http://www.pnas.org/content/early/2011/05/24/1019576108
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saatchi@jpl.nasa.gov  

Title

Development and application of a detailed inventory framework for estimating nitrous oxide and methane emissions from agriculture

Reference

Atmospheric Environment
Volume 45, Issue 7, March 2011, Pages 1454-1463

Author(s)

Junye Wang, Laura M. Cardenas, Tom H. Misselbrook and Sarah Gilhespy

Study type

Peer Review Journal

Abstract

A detailed inventory framework was developed to estimate nitrous oxide (N2O) and methane (CH4) emissions from UK agriculture using the IPCC approach. The inventory framework model was illustrated by combining relevant emission factors with agricultural census data for England, Wales, Scotland and Northern Ireland for the year 2000 to derive country-specific emission estimates which were summed to derive the UK total. The framework enables simple assessment to be made of the impact on national emissions of using different emission factors (EFs) (e.g. site- or local-specific compared with IPCC default factors). The framework was used to calculate the average annual emissions of nitrous oxide (N2O) and methane (CH4) for specific livestock and crops, and amounts lost through volatilisation, leaching and runoff for each country in the UK. The framework provides a simple, realistic and transparent approach to estimating national emissions and can easily be updated.

Policy theme(s)

Agriculture >> Agricultural pollution >> Agricultural emissions
Climate change and energy >> Greenhouse gas emissions >> Terrestrial emissions

Keywords

Methane, Inventory, Greenhouse gas emissions, Nitrous oxide

Entry Source:

Selected for Science for Environment Policy News Alert

Referred to in EC doc:

N/A

View this study at:

http://www.sciencedirect.com/science/article/pii/S135223101001040X
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junye.wang@bbsrc.ac.uk