| 1. |
- Azar, Christian, 1969, et al.
(författare)
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Meeting global temperature targets-the role of bioenergy with carbon capture and storage
- 2013
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9318 .- 1748-9326. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- In order to meet stringent temperature targets, active removal of CO2 from the atmosphere may be required in the long run. Such negative emissions can be materialized when well-performing bioenergy systems are combined with carbon capture and storage (BECCS). Here, we develop an integrated global energy system and climate model to evaluate the role of BECCS in reaching ambitious temperature targets. We present emission, concentration and temperature pathways towards 1.5 and 2 degrees C targets. Our model results demonstrate that BECCS makes it feasible to reach temperature targets that are otherwise out of reach, provided that a temporary overshoot of the target is accepted. Additionally, stringent temperature targets can be met at considerably lower cost if BECCS is available. However, the economic benefit of BECCS nearly vanishes if an overshoot of the temperature target is not allowed. Finally, the least-cost emission pathway over the next 50 years towards a 1.5 degrees C overshoot target with BECCS is almost identical to a pathway leading to a 2 degrees C ceiling target.
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| 2. |
- Milne, Eleanor, et al.
(författare)
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Methods for the quantification of GHG emissions at the landscape level for developing countries in smallholder contexts
- 2013
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Ingår i: Environmental Research Letters. - : Institute of Physics: Open Access Journals / Institute of Physics (IoP). - 1748-9326 .- 1748-9318. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Landscape scale quantification enables farmers to pool resources and expertise. However, the problem remains of how to quantify these gains. This article considers current greenhouse gas (GHG) quantification methods that can be used in a landscape scale analysis in terms of relevance to areas dominated by smallholders in developing countries. In landscape scale carbon accounting frameworks, measurements are an essential element. Sampling strategies need careful design to account for all pools/fluxes and to ensure judicious use of resources. Models can be used to scale-up measurements and fill data gaps. In recent years a number of accessible models and calculators have been developed which can be used at the landscape scale in developing country areas. Some are based on the Intergovernmental Panel on Climate Change (IPCC) method and others on dynamic ecosystem models. They have been developed for a range of different purposes and therefore vary in terms of accuracy and usability. Landscape scale assessments of GHGs require a combination of ground sampling, use of data from census, remote sensing (RS) or other sources and modelling. Fitting of all of these aspects together needs to be performed carefully to minimize uncertainties and maximize the use of scarce resources. This is especially true in heterogeneous landscapes dominated by smallholders in developing countries.
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| 3. |
- Wu, Chaoyang, et al.
(författare)
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An underestimated role of precipitation frequency in regulating summer soil moisture
- 2012
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 7:2, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Soil moisture induced droughts are expected to become more frequent under future global climate change. Precipitation has been previously assumed to be mainly responsible for variability in summer soil moisture. However, little is known about the impacts of precipitation frequency on summer soil moisture, either interannually or spatially. To better understand the temporal and spatial drivers of summer drought, 415 site yr measurements observed at 75 flux sites world wide were used to analyze the temporal and spatial relationships between summer soil water content (SWC) and the precipitation frequencies at various temporal scales, i.e., from half-hourly, 3, 6, 12 and 24 h measurements. Summer precipitation was found to be an indicator of interannual SWC variability with r of 0.49 (p < 0.001) for the overall dataset. However, interannual variability in summer SWC was also significantly correlated with the five precipitation frequencies and the sub-daily precipitation frequencies seemed to explain the interannual SWC variability better than the total of precipitation. Spatially, all these precipitation frequencies were better indicators of summer SWC than precipitation totals, but these better performances were only observed in non-forest ecosystems. Our results demonstrate that precipitation frequency may play an important role in regulating both interannual and spatial variations of summer SWC, which has probably been overlooked or underestimated. However, the spatial interpretation should carefully consider other factors, such as the plant functional types and soil characteristics of diverse ecoregions.
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| 4. |
- Abdi, Hakim, et al.
(författare)
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The supply and demand of net primary production in the Sahel
- 2014
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 9:9, s. 11-094003
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Tidskriftsartikel (refereegranskat)abstract
- Net primary production (NPP) is the principal source of energy for ecosystems and, by extension, human populations that depend on them. The relationship between the supply and demand of NPP is important for the assessment of socio-ecological vulnerability. We present an analysis of the supply and demand of NPP in the Sahel using NPP estimates from the MODIS sensor and agri-environmental data from FAOSTAT. This synergistic approach allows for a spatially explicit estimation of human impact on ecosystems. We estimated the annual amount of NPP required to derive food, fuel and feed between 2000 and 2010 for 22 countries in sub-Saharan Africa. When comparing annual estimates of supply and demand of NPP, we found that demand increased from 0.44 PgC to 1.13 PgC, representing 19% and 41%, respectively, of available supply due to a 31% increase in the human population between 2000 and 2010. The demand for NPP has been increasing at an annual rate of 2.2% but NPP supply was near-constant with an inter-annual variability of approximately 1.7%. Overall, there were statistically significant (p < 0.05) increases in the NPP of cropland (+6.0%), woodland (+6.1%) and grassland/savanna (+9.4%), and a decrease in the NPP of forests (−0.7%). On the demand side, the largest increase was for food (20.4%) followed by feed (16.7%) and fuel (5.5%). The supply-demand balance of NPP is a potentially important tool from the standpoint of sustainable development, and as an indicator of stresses on the environment stemming from increased consumption of biomass.
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| 5. |
- Ahlström, Anders, et al.
(författare)
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Robustness and uncertainty in terrestrial ecosystem carbon response to CMIP5 climate change projections
- 2012
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the spatio-temporal carbon balance patterns resulting from forcing a dynamic global vegetation model with output from 18 climate models of the CMIP5 (Coupled Model Intercomparison Project Phase 5) ensemble. We found robust patterns in terms of an extra-tropical loss of carbon, except for a temperature induced shift in phenology, leading to an increased spring uptake of carbon. There are less robust patterns in the tropics, a result of disagreement in projections of precipitation and temperature. Although the simulations generally agree well in terms of the sign of the carbon balance change in the middle to high latitudes, there are large differences in the magnitude of the loss between simulations. Together with tropical uncertainties these discrepancies accumulate over time, resulting in large differences in total carbon uptake over the coming century (−0.97–2.27 Pg C yr −1 during 2006–2100). The terrestrial biosphere becomes a net source of carbon in ten of the 18 simulations adding to the atmospheric CO 2 concentrations, while the remaining eight simulations indicate an increased sink of carbon.
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| 6. |
- Heinonen, Jukka, et al.
(författare)
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Dense downtown living more carbon intense due to higher consumption : A case study of Helsinki
- 2011
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 6:3
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Tidskriftsartikel (refereegranskat)abstract
- Hindering urban sprawl is one of the main goals for contemporary urban planning. Urban density is considered crucial in climate change mitigation since it reduces automobile dependence and decreases unit sizes, for example. This letter analyzes the effect of density in a city context. In the study the Finnish capital Helsinki is divided into two areas of different urban densities: the high density downtown area and the more scarcely populated suburbs. The study is a continuation of a recently published study on the implications of urban structure on carbon emissions, and analyzes further the main finding of the first study - that higher urban density might have negligible or even reverse effect on the per capita carbon emissions. Similarly to the previous study, a consumption based tiered hybrid life cycle assessment (LCA) approach is employed in order to produce a comprehensive assessment, free of territorial boundaries and system cutoffs typical of traditional LCAs. Based on the findings of the previous study, it is hypothesized that when assessing city level carbon dioxide emissions from a wider, consumer oriented LCA perspective, increased urban density may not necessarily reduce carbon emissions. Surprisingly, the study finds that carbon dioxide equivalent (CO2e) emissions are substantially higher in the dense downtown area than in the surrounding suburbs, which is suggested to imply that the increased consumption due to the higher standard of living increases emissions more than the higher density is able to reduce them. The results demonstrate that, while increasing urban density can be justified from a number of ecological, social and economic viewpoints, density is not necessarily a key parameter in the particular case of climate change. In cities like Helsinki, where wealth is concentrated in the downtown area, climate policies should give higher priority to the energy consumption of buildings, to alternative energy production and distribution modes, as well as to low carbon consumption within the city.
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| 7. |
- Johansson, Margareta, et al.
(författare)
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Rapid responses of permafrost and vegetation to experimentally increased snow cover in sub-arctic Sweden
- 2013
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- Increased snow depth already observed, and that predicted for the future are of critical importance to many geophysical and biological processes as well as human activities. The future characteristics of sub-arctic landscapes where permafrost is particularly vulnerable will depend on complex interactions between snow cover, vegetation and permafrost. An experimental manipulation was, therefore, set up on a lowland peat plateau with permafrost, in northernmost Sweden, to simulate projected future increases in winter precipitation and to study their effects on permafrost and vegetation. After seven years of treatment, statistically significant differences between manipulated and control plots were found in mean winter ground temperatures, which were 1.5 degrees C higher in manipulated plots. During the winter, a difference in minimum temperatures of up to 9 degrees C higher could be found in individual manipulated plots compared with control plots. Active layer thicknesses increased at the manipulated plots by almost 20% compared with the control plots and a mean surface subsidence of 24 cm was recorded in the manipulated plots compared to 5 cm in the control plots. The graminoid Eriophorum vaginatum has expanded in the manipulated plots and the vegetation remained green longer in the season.
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| 8. |
- Lund, Magnus, et al.
(författare)
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Effects of drought conditions on the carbon dioxide dynamics in a temperate peatland
- 2012
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- Drought is arguably the most important regulator of inter-annual variation in net ecosystem CO2 exchange (NEE) in peatlands. This study investigates effects of drought periods on NEE and its components, gross primary production (GPP) and ecosystem respiration (R-eco), on the basis of eddy covariance measurements of land-atmosphere exchange of CO2 in 2006-2009 in a south Swedish nutrient-poor peatland. Two drought periods had dissimilar effects on the CO2 exchange. In 2006, there was a short but severe drought period in the middle of the growing season resulting in increased R-eco rates, but no detectable effect on GPP rates. In contrast, in 2008 the drought period began early in the growing season and lasted for a longer period of time, resulting in reduced GPP rates, suggesting that GPP is most sensitive to drought during leaf out and canopy development compared with the full canopy stage. Both in 2006 and in 2008 the peatland acted as an annual source of atmospheric CO2, while in 2007 and 2009, when there were no drought periods, the peatland constituted a CO2 sink. It was concluded that the timing, severity and duration of drought periods regulate the effects on peatland GPP, R-eco and NEE.
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| 9. |
- Olefeldt, D., et al.
(författare)
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Influence of the permafrost boundary on dissolved organic matter characteristics in rivers within the Boreal and Taiga plains of western Canada
- 2014
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Catchment export of terrestrial dissolved organic matter (DOM) and its downstream degradation in aquatic ecosystems are important components of landscape scale carbon balances. In order to assess the influence of peatland permafrost on river DOM characteristics, we sampled 65 rivers along a 900 km transect crossing into the southern discontinuous permafrost zone on the Boreal and Tundra Plains of western Canada. Catchment peatland cover and catchment location north or south of the permafrost boundary were found together to have strong influences on dissolved organic carbon (DOC) concentrations and DOM chemical composition. River DOC concentrations increased with catchment peatland cover, but were consistently lower for catchments north of the permafrost boundary. In contrast, protein fluorescence (PARAFAC analysis), was unrelated to catchment peatland cover but increased significantly in rivers north of the permafrost boundary. Humic and fulvic acid contribution to DOM fluorescence was lower in rivers draining catchments with large lakes than in other rivers, consistent with extensive photodegradation, but humic and fulvic acid fluorescence were also lower in rivers north of the permafrost boundary than in rivers to the south. We hypothesize that shifts in river DOM characteristics when crossing the permafrost boundary are related to the influence of permafrost on peatland hydrological connectivity to stream networks, peatland DOM characteristics and differences in DOM degradation within aquatic ecosystems.
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| 10. |
- Peichl, Matthias, et al.
(författare)
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A 12-year record reveals pre-growing season temperature and water table level threshold effects on the net carbon dioxide exchange in a boreal fen
- 2014
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Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 9:5
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Tidskriftsartikel (refereegranskat)abstract
- This study uses a 12-year time series (2001-2012) of eddy covariance measurements to investigate the long-term net ecosystem exchange (NEE) of carbon dioxide (CO2) and inter-annual variations in relation to abiotic drivers in a boreal fen in northern Sweden. The peatland was a sink for atmospheric CO2 in each of the twelve study years with a 12-year average (+/- standard deviation) NEE of -58 +/- 21 g C m(-2) yr(-1). For ten out of twelve years, the cumulative annual NEE was within a range of -42 to -79 g C m(-2) yr(-1) suggesting a general state of resilience of NEE to moderate inter-annual climate variations. However, the annual NEE of -18 and -106 g C m(-2) yr(-1) in 2006 and 2008, respectively, diverged considerably from this common range. The lower annual CO2 uptake in 2006 was mainly due to late summer emissions related to an exceptional drop in water table level (WTL). A positive relationship (R-2 = 0.65) between pre-growing season (January to April) air temperature (Ta) and summer (June to July) gross ecosystem production (GEP) was observed. We suggest that enhanced GEP due to mild pre-growing season air temperature in combination with air temperature constraints on ecosystem respiration (ER) during the following cooler summer explained most of the greater net CO2 uptake in 2008. Differences in the annual and growing season means of other abiotic variables (e.g. radiation, vapor pressure deficit, precipitation) and growing season properties (i.e. start date, end date, length) were unable to explain the inter-annual variations of NEE. Overall, our findings suggest that this boreal fen acts as a persistent contemporary sink for atmospheric CO2 that is, however, susceptible to severe anomalies in WTL and pre-growing season air temperature associated with predicted changes in climate patterns for the boreal region.
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