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1:07:34 Institute of Physics (IOP) English 2011

Manipulating Graphene at the Atomic Scale

  • Published: 2011
  • Publisher: Institute of Physics (IOP)
  • Language: English
1:00:07 Institute of Physics (IOP) English 2011

Graphene and hexa-BN Heterostructures

  • Published: 2011
  • Publisher: Institute of Physics (IOP)
  • Language: English
1:04:10 Institute of Physics (IOP) English 2011

Graphene based Electronics and Optoelectronics

  • Published: 2011
  • Publisher: Institute of Physics (IOP)
  • Language: English
1:18:31 Institute of Physics (IOP) English 2011

Electronic Properties of Bilayer Graphene, from High to Low Energies

  • Published: 2011
  • Publisher: Institute of Physics (IOP)
  • Language: English
51:23 Institute of Physics (IOP) English 2011

Chiral Electrons and Zero-Mode Anomalies in Graphene

  • Published: 2011
  • Publisher: Institute of Physics (IOP)
  • Language: English
54:08 Institute of Physics (IOP) English 2011

Recent Progress in Graphene Synthesis and Applications

  • Published: 2011
  • Publisher: Institute of Physics (IOP)
  • Language: English
1:01:25 Institute of Physics (IOP) English 2011

Graphene Update

  • Published: 2011
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:03 Institute of Physics (IOP) English 2013

Bioenergy: how much can we expect for 2050?

Estimates of global primary bioenergy potentials in the literature span almost three orders of magnitude. We narrow that range by discussing biophysical constraints on bioenergy potentials resulting from plant growth (NPP) and its current human use. In the last 30 years, terrestrial NPP was almost constant near 54 PgC yr−1, despite massive efforts to increase yields in agriculture and forestry. The global human appropriation of terrestrial plant production has doubled in the last century. We estimate the maximum physical potential of the world's total land area outside croplands, infrastructure, wilderness and denser forests to deliver bioenergy at approximately 190 EJ yr−1. These pasture lands, sparser woodlands, savannas and tundras are already used heavily for grazing and store abundant carbon; they would have to be entirely converted to bioenergy and intensive forage production to provide that amount of energy. Such a high level of bioenergy supply would roughly double the global human biomass harvest, with far-reaching effects on biodiversity, ecosystems and food supply. Identifying sustainable levels of bioenergy and finding ways to integrate bioenergy with food supply and ecological conservation goals remains a huge and pressing scientific challenge.
  • Published: 2013
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:56 Institute of Physics (IOP) English 2013

Connecting plug-in vehicles with green electricity through consumer demand

The environmental benefits of plug-in electric vehicles (PEVs) increase if the vehicles are powered by electricity from 'green' sources such as solar, wind or small-scale hydroelectricity. Here, we explore the potential to build a market that pairs consumer purchases of PEVs with purchases of green electricity. We implement a web-based survey with three US samples defined by vehicle purchases: conventional new vehicle buyers (n = 1064), hybrid vehicle buyers (n = 364) and PEV buyers (n = 74). Respondents state their interest in a PEV as their next vehicle, in purchasing green electricity in one of three ways, i.e., monthly subscription, two-year lease or solar panel purchase, and in combining the two products. Although we find that a link between PEVs and green electricity is not presently strong in the consciousness of most consumers, the combination is attractive to some consumers when presented. Across all three respondent segments, pairing a PEV with a green electricity program increased interest in PEVs—with a 23% demand increase among buyers of conventional vehicles. Overall, about one-third of respondents presently value the combination of a PEV with green electricity; the proportion is much higher among previous HEV and PEV buyers. Respondents' reported motives for interest in both products and their combination include financial savings (particularly among conventional buyers), concerns about air pollution and the environment, and interest in new technology (particularly among PEV buyers). The results provide guidance regarding policy and marketing strategies to advance PEVs and green electricity demand.
  • Published: 2013
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:05 Institute of Physics (IOP) English 2014

Internal variability of Earth's energy budget simulated by CMIP5 climate models

We analyse a large number of multi-century pre-industrial control simulations from the fifth phase of the Coupled Model Intercomparison Project (CMIP5) to investigate relationships between: net top-of-atmosphere radiation (TOA), globally averaged surface temperature (GST), and globally integrated ocean heat content (OHC) on decadal timescales. Consistent with previous studies, we find that large trends (~0.3 K dec−1) in GST can arise from internal climate variability and that these trends are generally an unreliable indicator of TOA over the same period. In contrast, trends in total OHC explain 95% or more of the variance in TOA for two-thirds of the models analysed; emphasizing the oceans' role as Earth's primary energy store. Correlation of trends in total system energy (TE ≡ time integrated TOA) against trends in OHC suggests that for most models the ocean becomes the dominant term in the planetary energy budget on a timescale of about 12 months. In the context of the recent pause in global surface temperature rise, we investigate the potential importance of internal climate variability in both TOA and ocean heat rearrangement. The model simulations suggest that both factors can account for O (0.1 W m−2) on decadal timescales and may play an important role in the recently observed trends in GST and 0–700 m (and 0–1800 m) ocean heat uptake.
  • Published: 2014
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:53 Institute of Physics (IOP) English 2013

Changing the spatial location of electricity generation to increase water availability in areas with drought: a feasibility study and quantification of air quality impacts in Texas

The feasibility, cost, and air quality impacts of using electrical grids to shift water use from drought-stricken regions to areas with more water availability were examined. Power plant cooling represents a large portion of freshwater withdrawals in the United States, and shifting where electricity generation occurs can allow the grid to act as a virtual water pipeline, increasing water availability in regions with drought by reducing water consumption and withdrawals for power generation. During a 2006 drought, shifting electricity generation out of the most impacted areas of South Texas (~10% of base case generation) to other parts of the grid would have been feasible using transmission and power generation available at the time, and some areas would experience changes in air quality. Although expensive, drought-based electricity dispatch is a potential parallel strategy that can be faster to implement than other infrastructure changes, such as air cooling or water pipelines.
  • Published: 2013
  • Publisher: Institute of Physics (IOP)
  • Language: English
05:27 Institute of Physics (IOP) English 2014

A comparative analysis of the greenhouse gas emissions intensity of wheat and beef in the United States

The US food system utilizes large quantities of liquid fuels, electricity, and chemicals yielding significant greenhouse gas (GHG) emissions that are not considered in current retail prices, especially when the contribution of biogenic emissions is considered. However, because GHG emissions might be assigned a price in prospective climate policy frameworks, it would be useful to know the extent to which those policies would increase the incremental production costs to food within the US food system. This analysis uses lifecycle assessment (LCA) to (1) estimate the magnitude of carbon dioxide equivalent (CO2e) emissions from typical US food production practices, using wheat and beef as examples, and (2) quantify the cost of those emissions in the context of a GHG-pricing regime over a range of policy constructs. Wheat and beef were chosen as benchmark staples to provide a representative range of less intensive and more intensive agricultural goods, respectively. Results suggest that 1.1 ± 0.13 and 31 ± 8.1 kg of lifecycle CO2e emissions are embedded in 1 kg of wheat and beef production, respectively. Consequently, the cost of lifecycle CO2e emissions for wheat (i.e. cultivation, processing, transportation, storage, and end-use preparation) over an emissions price range of 10 and 85 per tonne CO2e is estimated to be between 0.01 and 0.09 per kg of wheat, respectively, which would increase total wheat production costs by approximately 0.3–2% per kg. By comparison, the estimated lifecycle CO2e price of beef over the same range of CO2e prices is between 0.31 and 2.60 per kg of beef, representing a total production cost increase of approximately 5–40% per kg based on average 2010 food prices. This range indicates that the incremental cost to total US food production might be anywhere between 0.63–5.4 Billion per year for grain and 3.70 and 32 Billion per year for beef based on CO2e emissions assuming that total production volumes stay the same.
  • Published: 2014
  • Publisher: Institute of Physics (IOP)
  • Language: English
02:24 Institute of Physics (IOP) English 2018

Global predictability of temperature extremes

Extreme temperatures are one of the leading causes of death and disease in both developed and developing countries, and heat extremes are projected to rise in many regions. To reduce risk, heatwave plans and cold weather plans have been effectively implemented around the world. However, much of the world's population is not yet protected by such systems, including many data-scarce but also highly vulnerable regions. In this study, we assess at a global level where such systems have the potential to be effective at reducing risk from temperature extremes, characterizing (1) long-term average occurrence of heatwaves and coldwaves, (2) seasonality of these extremes, and (3) short-term predictability of these extreme events three to ten days in advance. Using both the NOAA and ECMWF weather forecast models, we develop global maps indicating a first approximation of the locations that are likely to benefit from the development of seasonal preparedness plans and/or short-term early warning systems for extreme temperature. The extratropics generally show both short-term skill as well as strong seasonality; in the tropics, most locations do also demonstrate one or both. In fact, almost 5 billion people live in regions that have seasonality and predictability of heatwaves and/or coldwaves. Climate adaptation investments in these regions can take advantage of seasonality and predictability to reduce risks to vulnerable populations.
  • Published: 2018
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:48 Institute of Physics (IOP) English 2018

A decade of remotely sensed observations highlight complex processes linked to coastal permafrost bluff erosion in the Arctic

Eroding permafrost coasts are likely indicators and integrators of changes in the Arctic System as they are susceptible to the combined effects of declining sea ice extent, increases in open water duration, more frequent and impactful storms, sea-level rise, and warming permafrost. However, few observation sites in the Arctic have yet to link decadal-scale erosion rates with changing environmental conditions due to temporal data gaps. This study increases the temporal fidelity of coastal permafrost bluff observations using near-annual high spatial resolution (<1 m) satellite imagery acquired between 2008–2017 for a 9 km segment of coastline at Drew Point, Beaufort Sea coast, Alaska. Our results show that mean annual erosion for the 2007–2016 decade was 17.2 m yr−1, which is 2.5 times faster than historic rates, indicating that bluff erosion at this site is likely responding to changes in the Arctic System. In spite of a sustained increase in decadal-scale mean annual erosion rates, mean open water season erosion varied from 6.7 m yr−1 in 2010 to more than 22.0 m yr−1 in 2007, 2012, and 2016. This variability provided a range of coastal responses through which we explored the different roles of potential environmental drivers. The lack of significant correlations between mean open water season erosion and the environmental variables compiled in this study indicates that we may not be adequately capturing the environmental forcing factors, that the system is conditioned by long-term transient effects or extreme weather events rather than annual variability, or that other not yet considered factors may be responsible for the increased erosion occurring at Drew Point. Our results highlight an increase in erosion at Drew Point in the 21st century as well as the complexities associated with unraveling the factors responsible for changing coastal permafrost bluffs in the Arctic.
  • Published: 2018
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:18 Institute of Physics (IOP) English 2013

Effective information channels for reducing costs of environmentally- friendly technologies: evidence from residential PV markets

Realizing the environmental benefits of solar photovoltaics (PV) will require reducing costs associated with perception, informational gaps and technological uncertainties. To identify opportunities to decrease costs associated with residential PV adoption, in this letter we use multivariate regression models to analyze a unique, household-level dataset of PV adopters in Texas (USA) to systematically quantify the effect of different information channels on aspiring PV adopters' decision-making. We find that the length of the decision period depends on the business model, such as whether the system was bought or leased, and on special opportunities to learn, such as the influence of other PV owners in the neighborhood. This influence accrues passively through merely witnessing PV systems in the neighborhood, increasing confidence and motivation, as well as actively through peer-to-peer communications. Using these insights we propose a new framework to provide public information on PV that could drastically reduce barriers to PV adoption, thereby accelerating its market penetration and environmental benefits. This framework could also serve as a model for other distributed generation technologies.
  • Published: 2013
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:00 Institute of Physics (IOP) English 2017

Irrigation offsets wheat yield reductions from warming temperatures

Temperature increases due to climate change are expected to cause substantial reductions in global wheat yields. However, uncertainty remains regarding the potential role for irrigation as an adaptation strategy to offset heat impacts. Here we utilize over 7000 observations spanning eleven Kansas field-trial locations, 180 varieties, and 29 years to show that irrigation significantly reduces the negative impact of warming temperatures on winter wheat yields. Dryland wheat yields are estimated to decrease about eight percent for every one-degree Celsius increase in temperature, yet irrigation completely offsets this negative impact in our sample. As in previous studies, we find that important interactions exist between heat stress and precipitation for dryland production. Here, uniquely, we observe both dryland and irrigated trials side-by-side at the same locations and find that precipitation does not provide the same reduction in heat stress as irrigation. This is likely to be because the timing, intensity, and volume of water applications influence wheat yields, so the ability to irrigate—rather than relying on rainfall alone—has a stronger influence on heat stress. We find evidence of extensive differences of water-deficit stress impacts across varieties. This provides some evidence of the potential for adapting to hotter and drier climate conditions using optimal variety selection. Overall, our results highlight the critical role of water management for future global food security. Water scarcity not only reduces crop yields through water-deficit stress, but also amplifies the negative effects of warming temperatures.
  • Published: 2017
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:02 Institute of Physics (IOP) English 2012

Human impacts on terrestrial hydrology: climate change versus pumping and irrigation

Global climate change is altering terrestrial water and energy budgets, with subsequent impacts on surface and groundwater resources; recent studies have shown that local water management practices such as groundwater pumping and irrigation similarly alter terrestrial water and energy budgets over many agricultural regions, with potential feedbacks on weather and climate. Here we use a fully-integrated hydrologic model to directly compare effects of climate change and water management on terrestrial water and energy budgets of a representative agricultural watershed in the semi-arid Southern Great Plains, USA. At local scales, we find that the impacts of pumping and irrigation on latent heat flux, potential recharge and water table depth are similar in magnitude to the impacts of changing temperature and precipitation; however, the spatial distributions of climate and management impacts are substantially different. At the basin scale, the impacts on stream discharge and groundwater storage are remarkably similar. Notably, for the watershed and scenarios studied here, the changes in groundwater storage and stream discharge in response to a 2.5 °C temperature increase are nearly equivalent to those from groundwater-fed irrigation. Our results imply that many semi-arid basins worldwide that practice groundwater pumping and irrigation may already be experiencing similar impacts on surface water and groundwater resources to a warming climate. These results demonstrate that accurate assessment of climate change impacts and development of effective adaptation and mitigation strategies must account for local water management practices.
  • Published: 2012
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:20 Institute of Physics (IOP) English 2017

Limiting climate change: what's most worth doing?

Wynes and Nicholas (2017 Environ. Res. Lett. 12 074024) claim that some of the most important actions individuals can take to mitigate climate change have been overlooked, particularly in educational messages for adolescents, and estimate the potential impact of some of these, including having fewer children and living car free. These estimates raise questions that deserve serious analysis, but they are based only on the technical potential of the actions and do not consider the plasticity of the behaviors and the feasibility of policies to support them. The actions identified as having the greatest potential are lifestyle changes that accrue benefits over a lifetime or longer, so are not realistic alternatives to actions that can be enacted immediately. But presenting lifestyle choices and the relative impacts of different actions as discussion starters for adolescents could be promising, especially if the discussions highlight issues of behavioral plasticity, policy plasticity, and time scale. Research has identified design principles for interventions to achieve the strongest emissions reductions at time scales up to the decadal. Design principles for achieving longer-lasting changes deserve careful analytic attention, as well as a stronger focus in adolescent textbooks and messages to the general population. Both adolescents and researchers would do well to think carefully about what could promote the generational changes needed to reach a climate change target such as 'well below 2 °C'.
  • Published: 2017
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:26 Institute of Physics (IOP) English 2012

Can shrubs help to reconstruct historical glacier retreats?

In the 21st century, most of the world's glaciers are expected to retreat due to further global warming. The range of this predicted retreat varies widely as a result of uncertainties in climate and glacier models. To calibrate and validate glacier models, past records of glacier mass balance are necessary, which often only span several decades. Long-term reconstructions of glacier mass balance could increase the precision of glacier models by providing the required calibration data. Here we show the possibility of applying shrub growth increments as an on-site proxy for glacier summer mass balance, exemplified by Salix shrubs in Finse, Norway. We further discuss the challenges which this method needs to meet and address the high potential of shrub growth increments for reconstructing glacier summer mass balance in remote areas.
  • Published: 2012
  • Publisher: Institute of Physics (IOP)
  • Language: English
02:26 Institute of Physics (IOP) English 2013

Farm-scale costs and returns for second generation bioenergy cropping systems in the US Corn Belt

While grain crops are meeting much of the initial need for biofuels in the US, cellulosic or second generation (2G) materials are mandated to provide a growing portion of biofuel feedstocks. We sought to inform development of a 2G crop portfolio by assessing the profitability of novel cropping systems that potentially mitigate the negative effects of grain-based biofuel crops on food supply and environmental quality. We analyzed farm-gate costs and returns of five systems from an ongoing experiment in central Iowa, USA. The continuous corn cropping system was most profitable under current market conditions, followed by a corn–soybean rotation that incorporated triticale as a 2G cover crop every third year, and a corn–switchgrass system. A novel triticale–hybrid aspen intercropping system had the highest yields over the long term, but could only surpass the profitability of the continuous corn system when biomass prices exceeded foreseeable market values. A triticale/sorghum double cropping system was deemed unviable. We perceive three ways 2G crops could become more cost competitive with grain crops: by (1) boosting yields through substantially greater investment in research and development, (2) increasing demand through substantially greater and sustained investment in new markets, and (3) developing new schemes to compensate farmers for environmental benefits associated with 2G crops.
  • Published: 2013
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:15 Institute of Physics (IOP) English 2017

Cost-effectiveness of reducing emissions from tropical deforestation, 2016–2050

Reducing tropical deforestation is potentially a large-scale and low-cost strategy for mitigating climate change. Yet previous efforts to project the cost-effectiveness of policies to reduce greenhouse gas emissions from future deforestation across the tropics were hampered by crude available data on historical forest loss. Here we use recently available satellite-based maps of annual forest loss between 2001–2012, along with information on topography, accessibility, protected status, potential agricultural revenue, and an observed inverted-U-shaped relationship between forest cover loss and forest cover, to project tropical deforestation from 2016–2050 under alternative policy scenarios and to construct new marginal abatement cost curves for reducing emissions from tropical deforestation. We project that without new forest conservation policies 289 million hectares of tropical forest will be cleared from 2016–2050, releasing 169 GtCO2. A carbon price of US20/tCO2 (50/tCO2) across tropical countries would avoid 41 GtCO2 (77 GtCO2) from 2016–2050. By comparison, we estimate that Brazil's restrictive policies in the Amazon between 2004–2012 successfully decoupled potential agricultural revenue from deforestation and reduced deforestation by 47% below what would have otherwise occurred, preventing the emission of 5.2 GtCO2. All tropical countries enacting restrictive anti-deforestation policies as effective as those in the Brazilian Amazon between 2004–2012 would avoid 58 GtCO2 from 2016–2050.
  • Published: 2017
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:54 Institute of Physics (IOP) English 2014

Air pollution is pushing wind speed into a regulator of surface solar irradiance in China

Analysis in 27 cities across China shows that surface solar irradiance (SSI) and wind speed track similar decadal trends in 1961–2011, suggesting wind speed as a possible regulator of SSI. This assumption is further confirmed by the continuously widening gap in annually averaged daily SSI between windy and windless clear-sky days with worsening air pollution. Wider gaps are noted for more polluted cities and seasons. The gap in SSI between windy and windless conditions could therefore serve as a good indicator for air quality. The regulatory effect of wind speed on SSI starts to be important when air pollution index exceeds the boundary of 125. A plausible mechanism of wind speed regulating SSI through interactions with aerosols is proposed. There are two cut-off points of 2.5 m s−1 and 3.5 m s−1 wind speeds. Winds <2.5 m s−1 noticeably disperse air pollutants and thereby enhance SSI. Above the 2.5 m s−1 threshold, air pollution and SSI become largely insensitive to changing wind speeds. Winds in excess of 3.5 m s−1 could enhance aerosol concentration probably by inducing dust-storms, which in turn attenuate SSI.
  • Published: 2014
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:31 Institute of Physics (IOP) English 2014

Higher subsoil carbon storage in species-rich than species-poor temperate forests

Forest soils contribute ca. 70% to the global soil organic carbon (SOC) pool and thus are an important element of the global carbon cycle. Forests also harbour a large part of the global terrestrial biodiversity. It is not clear, however, whether tree species diversity affects SOC. By measuring the carbon concentration of different soil particle size fractions separately, we were able to distinguish between effects of fine particle content and tree species composition on the SOC pool in old-growth broad-leaved forest plots along a tree diversity gradient (1-, 3- and 5-species). Variation in clay content explained part of the observed SOC increase from monospecific to mixed forests, but we show that the carbon concentration per unit clay or fine silt in the subsoil was by 30–35% higher in mixed than monospecific stands indicating a significant species identity or species diversity effect on C stabilization. Underlying causes may be differences in fine root biomass and turnover, in leaf litter decomposition rate among the tree species, and/or species-specific rhizosphere effects on soil. Our findings may have important implications for forestry offering management options through preference of mixed stands that could increase forest SOC pools and mitigate climate warming.
  • Published: 2014
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:02 Institute of Physics (IOP) English 2018

Are Scots pine forest edges particularly prone to drought-induced mortality?

Climate change is expected to exacerbate the frequency of drought-induced tree mortality world-wide. To better predict the associated change of species composition and forest dynamics on various scales and develop adequate adaptation strategies, more information on the mechanisms driving the often observed patchiness of tree die-back is needed. Although forest-edge effects may play an important role within the given context, only few corresponding studies exist. Here, we investigate the regional die-back of Scots pine in Franconia, Germany, after a hot and dry summer in 2015, thereby emphasizing possible differences in mortality between forest edge and interior. By means of dendroecological investigations and close-range remote sensing, we assess long-term growth performance and current tree vitality along five different forest-edge distance gradients. Our results clearly indicate a differing growth performance between edge and interior trees, associated with a higher vulnerability to drought, increased mortality rates, and lower tree vitality at the forest edge. Prior long-lasting growth decline of dead trees compared to live trees suggests depletion of carbon reserves in course of a long-term drought persisting since the 1990s to be the cause of regional Scots pine die-back. These findings highlight the forest edge as a potential focal point of forest management adaptation strategies in the context of drought-induced mortality.
  • Published: 2018
  • Publisher: Institute of Physics (IOP)
  • Language: English
05:12 Institute of Physics (IOP) English 2013

Climate change mitigation policies and poverty in developing countries

Mitigation of the potential impacts of climate change is one of the leading policy concerns of the 21st century. However, there continues to be heated debate about the nature, the content and, most importantly, the impact of the policy actions needed to limit greenhouse gas emissions. One contributing factor is the lack of systematic evidence on the impact of mitigation policy on the welfare of the poor in developing countries. In this letter we consider two alternative policy scenarios, one in which only the Annex I countries take action, and the second in which the first policy is accompanied by a forest carbon sequestration policy in the non-Annex regions. Using an economic climate policy analysis framework, we assess the poverty impacts of the above policy scenarios on seven socio-economic groups in 14 developing countries. We find that the Annex-I-only policy is poverty friendly, since it enhances the competitiveness of non-Annex countries—particularly in agricultural production. However, once forest carbon sequestration incentives in the non-Annex regions are added to the policy package, the overall effect is to raise poverty in the majority of our sample countries. The reason for this outcome is that the dominant impacts of this policy are to raise returns to land, reduce agricultural output and raise food prices. Since poor households rely primarily on their own labor for income, and generally own little land, and since they also spend a large share of their income on food, they are generally hurt on both the earning and the spending fronts. This result is troubling, since forest carbon sequestration—particularly through avoided deforestation—is a promising, low cost option for climate change mitigation.
  • Published: 2013
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:08 Institute of Physics (IOP) English 2013

The FAOSTAT database of greenhouse gas emissions from agriculture

Greenhouse gas (GHG) emissions from agriculture, including crop and livestock production, forestry and associated land use changes, are responsible for a significant fraction of anthropogenic emissions, up to 30% according to the Intergovernmental Panel on Climate Change (IPCC). Yet while emissions from fossil fuels are updated yearly and by multiple sources—including national-level statistics from the International Energy Agency (IEA)—no comparable efforts for reporting global statistics for agriculture, forestry and other land use (AFOLU) emissions exist: the latest complete assessment was the 2007 IPCC report, based on 2005 emission data. This gap is critical for several reasons. First, potentially large climate funding could be linked in coming decades to more precise estimates of emissions and mitigation potentials. For many developing countries, and especially the least developed ones, this requires improved assessments of AFOLU emissions. Second, growth in global emissions from fossil fuels has outpaced that from AFOLU during every decade of the period 1961–2010, so the relative contribution of the latter to total climate forcing has diminished over time, with a need for regular updates. We present results from a new GHG database developed at FAO, providing a complete and coherent time series of emission statistics over a reference period 1961–2010, at country level, based on FAOSTAT activity data and IPCC Tier 1 methodology. We discuss results at global and regional level, focusing on trends in the agriculture sector and net deforestation. Our results complement those available from the IPCC, extending trend analysis to a longer historical period and, critically, beyond 2005 to more recent years. In particular, from 2000 to 2010, we find that agricultural emissions increased by 1.1% annually, reaching 4.6 Gt CO2 yr−1 in 2010 (up to 5.4–5.8 Gt CO2 yr−1 with emissions from biomass burning and organic soils included). Over the same decade 2000–2010, the ratio of agriculture to fossil fuel emissions has decreased, from 17.2% to 13.7%, and the decrease is even greater for the ratio of net deforestation to fossil fuel emissions: from 19.1% to 10.1%. In fact, in the year 2000, emissions from agriculture have been consistently larger—about 1.2 Gt CO2 yr−1 in 2010—than those from net deforestation.
  • Published: 2013
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:01 Institute of Physics (IOP) English 2014

Potential influence of the late Holocene climate on settled farming versus nomadic cattle herding in the Minusinsk Hollow, south-central Siberia

Prehistoric and early historic human cultures are known to be closely connected to and dependent on their natural environments. We test the hypothesis that climate change influenced the means of subsistence of ancient tribes and favored agricultural or cattle herding economic strategies. Our study area is the Khakass–Minusinsk Hollow, located in the foothills of the Sayan Mountains, south-central Siberia, which was, for a few millennia, a buffer zone for human migrations across the Great Eurasian Steppe. Three different methods (the Montane BioClimatic Model, MontBCliM; the biomization method; and the actualizm method) are employed to reconstruct vegetation taken from the fossil pollen of sediment cores in two mountain lakes at eleven time slices related to successive human cultures back to the mid-Holocene. MontBCliM model is used inversely to convert site paleo-vegetation into site paleo-climates. Climate-based regression models are developed and applied to reconstructed climates to evaluate possible pasture and grain crops for these time slices. Pollen-based reconstructions of the climate fluctuations uncovered several dry periods with steppe and forest-steppe and wetter periods with forests since 6000 BP. Grasslands increased by an order of magnitude during the dry periods and provided extensive open space suitable for pastoralism; however, both grain and pasture yields decreased during these dry periods. During wetter climates, both grain and pasture yields increased twofold and supported more fixed human settlements centered around farming and cattle herding. Thus, the dry periods favored pastoralist rather than farming activities. Conversely, tribes that practiced agriculture had some advantage in the wet periods.
  • Published: 2014
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:32 Institute of Physics (IOP) English 2018

Phenological mismatch in coastal western Alaska may increase summer season greenhouse gas uptake

High latitude ecosystems are prone to phenological mismatches due to climate change- driven advances in the growing season and changing arrival times of migratory herbivores. These changes have the potential to alter biogeochemical cycling and contribute to feedbacks on climate change by altering greenhouse gas (GHG) emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) through large regions of the Arctic. Yet the effects of phenological mismatches on gas fluxes are currently unexplored. We used a three-year field experiment that altered the start of the growing season and timing of grazing to investigate how phenological mismatch affects GHG exchange. We found early grazing increased mean GHG emission to the atmosphere despite lower CH4 emissions due to grazing-induced changes in vegetation structure that increased uptake of CO2. In contrast, late grazing reduced GHG emissions because greater plant productivity led to an increase in CO2 uptake that overcame the increase in CH4 emission. Timing of grazing was an important control on both CO2 and CH4 emissions, and net GHG exchange was the result of opposing fluxes of CO2 and CH4. N2O played a negligible role in GHG flux. Advancing the growing season had a smaller effect on GHG emissions than changes to timing of grazing in this study. Our results suggest that a phenological mismatch that delays timing of grazing relative to the growing season, a change which is already developing along in western coastal Alaska, will reduce GHG emissions to the atmosphere through increased CO2 uptake despite greater CH4 emissions.
  • Published: 2018
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:02 Institute of Physics (IOP) English 2016

Flared natural gas-based onsite atmospheric water harvesting (AWH) for oilfield operations

Natural gas worth tens of billions of dollars is flared annually, which leads to resource waste and environmental issues. This work introduces and analyzes a novel concept for flared gas utilization, wherein the gas that would have been flared is instead used to condense atmospheric moisture. Natural gas, which is currently being flared, can alternatively power refrigeration systems to generate the cooling capacity for large scale atmospheric water harvesting (AWH). This approach solves two pressing issues faced by the oil–gas industry, namely gas flaring, and sourcing water for oilfield operations like hydraulic fracturing, drilling and water flooding. Multiple technical pathways to harvest atmospheric moisture by using the energy of natural gas are analyzed. A modeling framework is developed to quantify the dependence of water harvest rates on flared gas volumes and ambient weather. Flaring patterns in the Eagle Ford Shale in Texas and the Bakken Shale in North Dakota are analyzed to quantify the benefits of AWH. Overall, the gas currently flared annually in Texas and North Dakota can harvest enough water to meet 11% and 65% of the water consumption in the Eagle Ford and the Bakken, respectively. Daily harvests of upto 30 000 and 18 000 gallons water can be achieved using the gas currently flared per well in Texas and North Dakota, respectively. In fifty Bakken sites, the water required for fracturing or drilling a new well can be met via onsite flared gas-based AWH in only 3 weeks, and 3 days, respectively. The benefits of this concept are quantified for the Eagle Ford and Bakken Shales. Assessments of the global potential of this concept are presented using data from countries with high flaring activity. It is seen that this waste-to-value conversion concept offers significant economic benefits while addressing critical environmental issues pertaining to oil–gas production.
  • Published: 2016
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:06 Institute of Physics (IOP) English 2013

Redefining agricultural yields: from tonnes to people nourished per hectare

Worldwide demand for crops is increasing rapidly due to global population growth, increased biofuel production, and changing dietary preferences. Meeting these growing demands will be a substantial challenge that will tax the capability of our food system and prompt calls to dramatically boost global crop production. However, to increase food availability, we may also consider how the world's crops are allocated to different uses and whether it is possible to feed more people with current levels of crop production. Of particular interest are the uses of crops as animal feed and as biofuel feedstocks. Currently, 36% of the calories produced by the world's crops are being used for animal feed, and only 12% of those feed calories ultimately contribute to the human diet (as meat and other animal products). Additionally, human-edible calories used for biofuel production increased fourfold between the years 2000 and 2010, from 1% to 4%, representing a net reduction of available food globally. In this study, we re-examine agricultural productivity, going from using the standard definition of yield (in tonnes per hectare, or similar units) to using the number of people actually fed per hectare of cropland. We find that, given the current mix of crop uses, growing food exclusively for direct human consumption could, in principle, increase available food calories by as much as 70%, which could feed an additional 4 billion people (more than the projected 2–3 billion people arriving through population growth). Even small shifts in our allocation of crops to animal feed and biofuels could significantly increase global food availability, and could be an instrumental tool in meeting the challenges of ensuring global food security.
  • Published: 2013
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:03 Institute of Physics (IOP) English 2017

Contamination of the Arctic reflected in microbial metagenomes from the Greenland ice sheet

Globally emitted contaminants accumulate in the Arctic and are stored in the frozen environments of the cryosphere. Climate change influences the release of these contaminants through elevated melt rates, resulting in increased contamination locally. Our understanding of how biological processes interact with contamination in the Arctic is limited. Through shotgun metagenomic data and binned genomes from metagenomes we show that microbial communities, sampled from multiple surface ice locations on the Greenland ice sheet, have the potential for resistance to and degradation of contaminants. The microbial potential to degrade anthropogenic contaminants, such as toxic and persistent polychlorinated biphenyls, was found to be spatially variable and not limited to regions close to human activities. Binned genomes showed close resemblance to microorganisms isolated from contaminated habitats. These results indicate that, from a microbiological perspective, the Greenland ice sheet cannot be seen as a pristine environment.
  • Published: 2017
  • Publisher: Institute of Physics (IOP)
  • Language: English
02:02 Institute of Physics (IOP) English 2017

Air pollution impacts on avian species via inhalation exposure and associated outcomes

Despite the well-established links between air pollution and human health, vegetation, and aquatic ecosystems, less attention has been paid to the potential impact of reactive atmospheric gases and aerosols on avian species. In this literature review, we summarize findings published since 1950 regarding avian responses to air pollution and discuss knowledge gaps that could be addressed in future studies. We find consistent evidence for adverse health impacts on birds attributable to exposure to gas-phase and particulate air pollutants, including carbon monoxide (CO), ozone (O3), sulfur dioxide (SO2), smoke, and heavy metals, as well as mixtures of urban and industrial emissions. Avian responses to air pollution include respiratory distress and illness, increased detoxification effort, elevated stress levels, immunosuppression, behavioral changes, and impaired reproductive success. Exposure to air pollution may furthermore reduce population density, species diversity, and species richness in bird communities.
  • Published: 2017
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:29 Institute of Physics (IOP) English 2015

Tipping point of a conifer forest ecosystem under severe drought

Drought-induced tree mortality has recently received considerable attention. Questions have arisen over the necessary intensity and duration thresholds of droughts that are sufficient to trigger rapid forest declines. The values of such tipping points leading to forest declines due to drought are presently unknown. In this study, we have evaluated the potential relationship between the level of tree growth and concurrent drought conditions with data of the tree growth-related ring width index (RWI) of the two dominant conifer species (Pinus edulis and Pinus ponderosa) in the Southwestern United States (SWUS) and the meteorological drought-related standardized precipitation evapotranspiration index (SPEI). In this effort, we determined the binned averages of RWI and the 11 month SPEI within the month of July within each bin of 30 of RWI in the range of 0–3000. We found a significant correlation between the binned averages of RWI and SPEI at the regional-scale under dryer conditions. The tipping point of forest declines to drought is predicted by the regression model as SPEItp = −1.64 and RWItp = 0, that is, persistence of the water deficit (11 month) with intensity of −1.64 leading to negligible growth for the conifer species. When climate conditions are wetter, the correlation between the binned averages of RWI and SPEI is weaker which we believe is most likely due to soil water and atmospheric moisture levels no longer being the dominant factor limiting tree growth. We also illustrate a potential application of the derived tipping point (SPEItp = −1.64) through an examination of the 2002 extreme drought event in the SWUS conifer forest regions. Distinguished differences in remote-sensing based NDVI anomalies were found between the two regions partitioned by the derived tipping point.
  • Published: 2015
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:37 Institute of Physics (IOP) English 2017

The climate mitigation gap: education and government recommendations miss the most effective individual actions

Current anthropogenic climate change is the result of greenhouse gas accumulation in the atmosphere, which records the aggregation of billions of individual decisions. Here we consider a broad range of individual lifestyle choices and calculate their potential to reduce greenhouse gas emissions in developed countries, based on 148 scenarios from 39 sources. We recommend four widely applicable high-impact (i.e. low emissions) actions with the potential to contribute to systemic change and substantially reduce annual personal emissions: having one fewer child (an average for developed countries of 58.6 tonnes CO2-equivalent (tCO2e) emission reductions per year), living car-free (2.4 tCO2e saved per year), avoiding airplane travel (1.6 tCO2e saved per roundtrip transatlantic flight) and eating a plant-based diet (0.8 tCO2e saved per year). These actions have much greater potential to reduce emissions than commonly promoted strategies like comprehensive recycling (four times less effective than a plant-based diet) or changing household lightbulbs (eight times less). Though adolescents poised to establish lifelong patterns are an important target group for promoting high-impact actions, we find that ten high school science textbooks from Canada largely fail to mention these actions (they account for 4% of their recommended actions), instead focusing on incremental changes with much smaller potential emissions reductions. Government resources on climate change from the EU, USA, Canada, and Australia also focus recommendations on lower-impact actions. We conclude that there are opportunities to improve existing educational and communication structures to promote the most effective emission-reduction strategies and close this mitigation gap.
  • Published: 2017
  • Publisher: Institute of Physics (IOP)
  • Language: English
04:13 Institute of Physics (IOP) English 2014

Commitment accounting of CO2 emissions

The world not only continues to build new coal-fired power plants, but built more new coal plants in the past decade than in any previous decade. Worldwide, an average of 89 gigawatts per year (GW yr–1) of new coal generating capacity was added between 2010 and 2012, 23 GW yr–1 more than in the 2000–2009 time period and 56 GW yr–1 more than in the 1990–1999 time period. Natural gas plants show a similar pattern. Assuming these plants operate for 40 years, the fossil-fuel burning plants built in 2012 will emit approximately 19 billion tons of CO2 (Gt CO2) over their lifetimes, versus 14 Gt CO2 actually emitted by all operating fossil fuel power plants in 2012. We find that total committed emissions related to the power sector are growing at a rate of about 4% per year, and reached 307 (with an estimated uncertainty of 192–439) Gt CO2 in 2012. These facts are not well known in the energy policy community, where annual emissions receive far more attention than future emissions related to new capital investments. This paper demonstrates the potential for 'commitment accounting' to inform public policy by quantifying future emissions implied by current investments.
  • Published: 2014
  • Publisher: Institute of Physics (IOP)
  • Language: English
03:04 Institute of Physics (IOP) English 2015

Modeling relationships between water table depth and peat soil carbon loss in Southeast Asian plantations

Plantation-associated drainage of Southeast Asian peatlands has accelerated in recent years. Draining exposes the upper peat layer to oxygen, leading to elevated decomposition rates and net soil carbon losses. Empirical studies indicate positive relationships between long-term water table (WT) depth and soil carbon loss rate in peatlands. These correlations potentially enable using WT depth as a proxy for soil carbon losses from peatland plantations. Here, we compile data from published research assessing WT depth and carbon balance in tropical plantations on peat. We model net carbon loss from subsidence studies, as well as soil respiration (heterotrophic and total) from closed chamber studies, as a function of WT depth. WT depth across all 12 studies and 59 sites is 67 ± 20 cm (mean ± standard deviation). Mean WT depth is positively related to net carbon loss, as well as soil respiration rate. Our models explain 45% of net carbon loss variation and 45–63% of soil respiration variation. At a 70 cm WT depth, the subsidence model suggests net carbon loss of 20 tC ha−1 yr−1 (95% confidence interval (CI) 18–22 tC ha−1 yr−1) for plantations drained for >2 yr. Closed chamber-measured total soil respiration at this depth is 20 tC-CO2 ha−1 yr−1 (CI 17–24 tC-CO2 ha−1 yr−1) while heterotrophic respiration is 17 tC-CO2 ha−1 yr−1 (CI 14–20 tC-CO2 ha−1 yr−1), ~82% of total respiration. While land use is not a significant predictor of soil respiration, WT depths are greater at acacia (75 ± 16 cm) than oil palm (59 ± 15 cm) sample sites. Improved spatio-temporal sampling of the full suite of peat soil carbon fluxes—including fluvial carbon export and organic fertilizer inputs—will clarify multiple mechanisms leading to carbon loss and gain, supporting refined assessments of the global warming potential of peatland drainage.
  • Published: 2015
  • Publisher: Institute of Physics (IOP)
  • Language: English
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