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  • Wyser, Klaus, et al. (författare)
  • Warmer climate projections in EC-Earth3-Veg : The role of changes in the greenhouse gas concentrations from CMIP5 to CMIP6
  • Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9318 .- 1748-9326. ; 15:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Climate projections for the 21st century for CMIP6 are warmer than those for CMIP5 despite nominally identical instantaneous radiative forcing. Many climate modeling groups attribute the stronger warming in the CMIP6 projections to the higher climate sensitivity of the new generation of climate models, but here we demonstrate that also changes in the forcing datasets can play an important role, in particular the prescribed concentrations of greenhouse gases (GHG) that are used to force the models. In the EC-Earth3-Veg model the effective radiative forcing (ERF) is reduced by 1.4 W m-2 when the GHG concentrations from SSP5-8.5 (used in CMIP6) are replaced by the GHG concentrations from RCP8.5 (used in CMIP5), and similar yet smaller reductions are seen for the SSP2-4.5/RCP4.5 and SSP1-2.6/RCP2.6 scenario pairs. From the reduced ERF we can estimate the temperature at the end of the century in a full climate simulation with the CMIP6 version of the EC-Earth model but using CMIP5 GHG concentrations instead. For the new SSP5-8.5 and SSP2-4.5 scenarios we find that 50% or more of the temperature increase from CMIP5 to CMIP6 at the end of the century is due to changes in the prescribed GHG concentrations. The implication is that CMIP5 and CMIP6 projections for the 21st century are difficult to compare with each other not only as models differ but also as the forcing conditions are not equal. Therefore, the communication of CMIP6 results to the impact, mitigation and adaptation communities has to be carefully formulated, taking into account the role of the updated GHG concentrations when interpreting the warmer climate projections for the 21st century.
  • Pei, Lin, et al. (författare)
  • Climate variability or anthropogenic emissions: which caused Beijing Haze?
  • 2020
  • Ingår i: Environmental Research Letters. - 1748-9318 .- 1748-9326. ; 15:3
  • Tidskriftsartikel (refereegranskat)abstract
    • © 2020 The Author(s). Published by IOP Publishing Ltd. Beijing Haze has been phenomenal, especially for winter, and widely considered a result of the increasing anthropogenic emissions of atmospheric pollutants in the region. Since 2013, the pollutant emissions have been reduced with the help of a series of emission-control actions. However, severe haze events still occurred frequently in Beijing in recent winters, e.g., those of 2015 and 2016, implying that other factors such as meteorological conditions and interannual climate variability have also played an important role in forming the haze. Based on homogenized station observations, atmospheric circulation reanalysis and anthropogenic emissions data for the period 1980-2017, this paper attempts to quantify the relative importance of anthropogenic emissions and climatic conditions to the frequency and intensity of Beijing Haze in winter. It is found that the frequency (number) of hazy days exhibits large interannual variability and little trend, and its variations were mainly controlled by climate variability, with a correlation coefficient of 0.77. On the other hand, the intensity of haze displays strong interannual variability and a significant increasing trend during 1980-2012 and a notable decreasing trend during 2012-2017. The multiple linear regression model suggests that about half of the total variance of the haze intensity is explained by climate variability (mainly for interannual variations), and another half by the changing emissions (mainly for the trends).
  • Tlusty, Micheal, et al. (författare)
  • Commentary : Comparing efficiency in aquatic and terrestrial animal production systems
  • 2018
  • Ingår i: Environmental Research Letters. - : Institute of Physics Publishing. - 1748-9318 .- 1748-9326. ; 13:12
  • Tidskriftsartikel (refereegranskat)abstract
    • Aquaculture is receiving increased attention from a variety of stakeholders. This is largely due to its current role in the global food system of supplying more than half of the seafood consumed, and also because the industry continues to steadily expand (UN Food and Agriculture Organization 2018). A recent article in Environmental Research Letters, 'Feed conversion efficiency in aquaculture: Do we measure it correctly?', by Fry et al (2018a) found that measuring feed conversion efficiency of selected aquatic and terrestrial farmed animals using protein and calorie retention resulted in species comparisons (least to most efficient) and overlap among species dissimilar from comparisons based on widely used weight-based feed conversion ratio (FCR) values. The study prompted spirited discussions among researchers, industry representatives, and others. A group assembled to write a standard rebuttal, but during this process, decided it was best to engage the study's original authors to join the discourse. Through this collaboration, we provide the resultant additional context relevant to the study in order to advance conversations and research on the use of efficiency measures in aquatic and terrestrial animal production systems.
  • Vowles, Tage, et al. (författare)
  • Contrasting impacts of reindeer grazing in two tundra grasslands
  • 2017
  • Ingår i: Environmental Research Letters. - 1748-9318 .- 1748-9326. ; 12:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Plant communities in Arctic and alpine areas are changing due to higher temperatures and longer vegetation periods and it is uncertain how this will affect plant-herbivore dynamics. For instance, relatively fast-growing, deciduous shrub species that are the most responsive to warming may also be the most targeted by herbivores such as reindeer, giving less palatable evergreen shrubs the chance to expand. Using herbivore exclosures, we have studied how two grasslands with contrasting nutrient and moisture regimes, a dry, nutrient-poor alpine grass heath and a wet, productive low herb meadow, changed between 1995 and 2012, in grazed and ungrazed conditions. At the grass heath, evergreen low shrub abundance had more than doubled, regardless of grazer treatment, whereas at the low herb meadow, evergreen shrubs had increased only outside exclosures while deciduous tall shrubs and forbs were significantly more abundant inside exclosures. Deciduous tall shrubs were also significantly taller in exclosures. These contrasting findings suggest that the impact of herbivores is to a great deal determined by their influence on competitive interactions between plant species, and therefore depends on the underlying composition of the plant community. Consequently, as the balance in these competitive interactions is shifting due to climate warming, we conclude that the potential of herbivory to influence this balance is considerable yet highly site dependent.
  • Zu Ermgassen, Erasmus K.H.J., et al. (författare)
  • Using supply chain data to monitor zero deforestation commitments: an assessment of progress in the Brazilian soy sector
  • 2020
  • Ingår i: Environmental Research Letters. - 1748-9326 .- 1748-9318. ; 15:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Zero deforestation commitments (ZDCs) are voluntary initiatives where companies or countries pledge to eliminate deforestation from their supply chains. These commitments offer much promise for sustainable commodity production, but are undermined by a lack of transparency about their coverage and impacts. Here, using state-of-the-art supply chain data, we introduce an approach to evaluate the impact of ZDCs, linking traders and international markets to commodity-associated deforestation in the sub-national jurisdictions from which they source. We focus on the Brazilian soy sector, where we find that ZDC coverage is increasing, but under-represents the Cerrado biome where most soy-associated deforestation currently takes place. Though soy-associated deforestation declined in the Amazon after the introduction of the Soy Moratorium, we observe no change in the exposure of companies or countries adopting ZDCs to soy-associated deforestation in the Cerrado. We further assess the formulation and implementation of these ZDCs and identify several systematic weaknesses that must be addressed to increase the likelihood that they achieve meaningful reductions in deforestation in future. As the 2020 deadline for several of these commitments approaches, our approach can provide independent monitoring of progress toward the goal of ending commodity-associated deforestation.
  • Wu, Chaoyang, et al. (författare)
  • An underestimated role of precipitation frequency in regulating summer soil moisture
  • 2012
  • Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 7:2, s. 1-9
  • 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.
  • Abdi, Hakim, et al. (författare)
  • The supply and demand of net primary production in the Sahel
  • 2014
  • Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 9:9, s. 11-094003
  • 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.
  • Ahlström, Anders, et al. (författare)
  • Importance of vegetation dynamics for future terrestrial carbon cycling
  • 2015
  • Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 10:5
  • Tidskriftsartikel (refereegranskat)abstract
    • Terrestrial ecosystems currently sequester about one third of anthropogenic CO 2 emissions each year, an important ecosystem service that dampens climate change. The future fate of this net uptake of CO 2 by land based ecosystems is highly uncertain. Most ecosystem models used to predict the future terrestrial carbon cycle share a common architecture, whereby carbon that enters the system as net primary production (NPP) is distributed to plant compartments, transferred to litter and soil through vegetation turnover and then re-emitted to the atmosphere in conjunction with soil decomposition. However, while all models represent the processes of NPP and soil decomposition, they vary greatly in their representations of vegetation turnover and the associated processes governing mortality, disturbance and biome shifts. Here we used a detailed second generation dynamic global vegetation model with advanced representation of vegetation growth and mortality, and the associated turnover. We apply an emulator that describes the carbon flows and pools exactly as in simulations with the full model. The emulator simulates ecosystem dynamics in response to 13 different climate or Earth system model simulations from the Coupled Model Intercomparison Project Phase 5 ensemble under RCP8.5 radiative forcing. By exchanging carbon cycle processes between these 13 simulations we quantified the relative roles of three main driving processes of the carbon cycle; (I) NPP, (II) vegetation dynamics and turnover and (III) soil decomposition, in terms of their contribution to future carbon (C) uptake uncertainties among the ensemble of climate change scenarios. We found that NPP, vegetation turnover (including structural shifts, wild fires and mortality) and soil decomposition rates explained 49%, 17% and 33%, respectively, of uncertainties in modelled global C-uptake. Uncertainty due to vegetation turnover was further partitioned into stand-clearing disturbances (16%), wild fires (0%), stand dynamics (7%), reproduction (10%) and biome shifts (67%) globally. We conclude that while NPP and soil decomposition rates jointly account for 83% of future climate induced C-uptake uncertainties, vegetation turnover and structure, dominated by biome shifts, represent a significant fraction globally and regionally (tropical forests: 40%), strongly motivating their representation and analysis in future C-cycle studies.
  • Ahlström, Anders, et al. (författare)
  • The large influence of climate model bias on terrestrial carbon cycle simulations
  • 2017
  • Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 12:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Global vegetation models and terrestrial carbon cycle models are widely used for projecting the carbon balance of terrestrial ecosystems. Ensembles of such models show a large spread in carbon balance predictions, ranging from a large uptake to a release of carbon by the terrestrial biosphere, constituting a large uncertainty in the associated feedback to atmospheric CO 2 concentrations under global climate change. Errors and biases that may contribute to such uncertainty include ecosystem model structure, parameters and forcing by climate output from general circulation models (GCMs) or the atmospheric components of Earth system models (ESMs), e.g. as prepared for use in IPCC climate change assessments. The relative importance of these contributing factors to the overall uncertainty in carbon cycle projections is not well characterised. Here we investigate the role of climate model-derived biases by forcing a single global ecosystem-carbon cycle model, with original climate outputs from 15 ESMs and GCMs from the CMIP5 ensemble. We show that variation among the resulting ensemble of present and future carbon cycle simulations propagates from biases in annual means of temperature, precipitation and incoming shortwave radiation. Future changes in carbon pools, and thus land carbon sink trends, are also affected by climate biases, although to a smaller extent than the absolute size of carbon pools. Our results suggest that climate biases could be responsible for a considerable fraction of the large uncertainties in ESM simulations of land carbon fluxes and pools, amounting to about 40% of the range reported for ESMs. We conclude that climate bias-induced uncertainties must be decreased to make accurate coupled atmosphere-carbon cycle projections.
  • Blok, Daan, et al. (författare)
  • The response of Arctic vegetation to the summer climate: relation between shrub cover, NDVI, surface albedo and temperature
  • 2011
  • Ingår i: Environmental Research Letters. - : IOP Publishing. - 1748-9326. ; 6:3, s. 035502-035502
  • Tidskriftsartikel (refereegranskat)abstract
    • Recently observed Arctic greening trends from normalized difference vegetation index (NDVI) data suggest that shrub growth is increasing in response to increasing summer temperature. An increase in shrub cover is expected to decrease summer albedo and thus positively feed back to climate warming. However, it is unknown how albedo and NDVI are affected by shrub cover and inter-annual variations in the summer climate. Here, we examine the relationship between deciduous shrub fractional cover, NDVI and albedo using field data collected at a tundra site in NE Siberia. Field data showed that NDVI increased and albedo decreased with increasing deciduous shrub cover. We then selected four Arctic tundra study areas and compiled annual growing season maximum NDVI and minimum albedo maps from MODIS satellite data (2000–10) and related these satellite products to tundra vegetation types (shrub, graminoid, barren and wetland tundra) and regional summer temperature. We observed that maximum NDVI was greatest in shrub tundra and that inter-annual variation was negatively related to summer minimum albedo but showed no consistent relationship with summer temperature. Shrub tundra showed higher albedo than wetland and barren tundra in all four study areas. These results suggest that a northwards shift of shrub tundra might not lead to a decrease in summer minimum albedo during the snow-free season when replacing wetland tundra. A fully integrative study is however needed to link results from satellite data with in situ observations across the Arctic to test the effect of increasing shrub cover on summer albedo in different tundra vegetation types.
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