• Authors:
    • Mastrandrea, M. D.
    • Luers, A. L.
  • Source: CLIMATIC CHANGE
  • Volume: 111
  • Issue: 1
  • Year: 2012
  • Summary: Even with aggressive global action to reduce greenhouse gas emissions, the climate will continue to change for decades due to previous emissions and the inertia in biogeophysical and social systems. Therefore, as a complement to mitigation actions, society must also focus on enhancing its capacity to adapt to the unavoidable impacts of climate change that we are already experiencing and will continue to experience over the next few decades. Resource managers, regional planners, and government agencies need to consider climate risks in their planning. We provide an overview of climate change scenarios for California and suggestions on the use of climate projections in state and regional planning efforts in the future.
  • Authors:
    • Knox, N. M.
    • Grunwald, S.
    • Deenik, J. L.
    • Bruland, G. L.
    • McDowell, M. L.
  • Source: GEODERMA
  • Volume: 189
  • Year: 2012
  • Summary: Accurate assessment of total carbon (C-t) content is important for fertility and nutrient management of soils, as well as for carbon sequestration studies. The non-destructive analysis of soils by diffuse reflectance spectroscopy (DRS) is a potential supplement or alternative to the traditional time-consuming and costly combustion method of C-t analysis, especially in spatial or temporal studies where sample numbers are large. This alternative technique has been utilized in several locations in the United States and elsewhere, but has not been tested on the unique and diverse tropical soils in Hawaii. This study investigated the feasibility of DRS for C-t prediction of Hawaiian agricultural soils by creating visible, near-infrared (VNIR) and mid-infrared (MIR) spectral libraries and developing chemometric models with partial least squares regression (PLSR) and random forests (RF) ensemble tree regression. The sample set contained 305 soils from across the five main Hawaiian Islands, representing 10 soil orders and over 100 soil series. The C-t of these samples measured by dry combustion ranged from <1% to 56%, greater than that of most previously published studies. The VNIR spectra of the soils commonly exhibited features associated with OH- and H2O, iron oxides, phyllosilicates, and organic molecules. The numerous features in the MIR spectra can be attributed to OH-, organic molecules, and a variety of silicate minerals, such as phyllosilicates and quartz. Excellent results were obtained from both PLSR models using VNIR and MIR spectra. The models had R-2 values of 0.95/0.94 (VNIR/MIR), root mean squared error (RMSE) values of 2.80%/3.08%, residual prediction deviation (RPD) values of 4.25/3.91, and ratio of performance to inter-quartile distance (RPIQ) values of 3.66/3.38. The RF VNIR and MIR models were also of high quality, with R-2=0.95/0.96 (VNIR/MIR), RMSE=2.82%/228%, RPD=427/5.28, and RPIQ=3.68/4.56. An evaluation of the different wavelength ranges and chemometric methods determined that for this sample set all were capable of robust predictions of C-t. These results indicate that DRS is an alternative technique for analysis of C-t in Hawaiian soils. (C) 2012 Elsevier B.V. All rights reserved.
  • Authors:
    • Chowell, G.
    • Grossman-Clarke, S.
    • Harlan, S. L.
    • Ruddell, D.
  • Source: CLIMATIC CHANGE
  • Volume: 111
  • Issue: 3-4
  • Year: 2012
  • Summary: Understanding public perceptions of climate is critical for developing an effective strategy to mitigate the effects of human activity on the natural environment and reduce human vulnerability to the impacts of climate change. While recent climate assessments document change among various physical systems (e. g., increased temperature, sea level rise, shrinking glaciers), environmental perceptions are relatively under-researched despite the fact that there is growing skepticism and disconnect between climate science and public opinion. This study utilizes a socio-ecological research framework to investigate how public perceptions compared with environmental conditions in one urban center. Specifically, air temperature during an extreme heat event was examined as one characteristic of environmental conditions by relating simulations from the Weather Research and Forecast (WRF) atmospheric model with self-reported perceptions of regional and neighborhood temperatures from a social survey of Phoenix, AZ (USA) metropolitan area residents. Results indicate that: 1) human exposure to high temperatures varies substantially throughout metropolitan Phoenix; 2) public perceptions of temperature are more strongly correlated with proximate environmental conditions than with distal conditions; and 3) perceptions of temperature are related to social characteristics and situational variables. The social constructionist paradigm explains public perceptions at the regional scale, while experience governs attitude formation at the neighborhood scale.
  • Authors:
    • Kalkstein, L. S.
    • Allen, M. J.
    • Lee, C. C.
    • Sheridan, S. C.
  • Source: CLIMATIC CHANGE
  • Volume: 115
  • Issue: 2
  • Year: 2012
  • Summary: Excessive heat significantly impacts the health of Californians during irregular but intense heat events. Through the 21st century, a significant increase in impact is likely, as the state experiences a changing climate as well as an aging population. To assess this impact, future heat-related mortality estimates were derived for nine metropolitan areas in the state for the remainder of the century. Here in Part I, changes in oppressive weather days and consecutive-day events are projected for future years by a synoptic climatological method. First, historical surface weather types are related to circulation patterns at 500mb and 700mb, and temperature patterns at 850mb. GCM output is then utilized to classify future circulation patterns via discriminant function analysis, and multinomial logistic regression is used to derive future surface weather type at each of six stations in California. Five different climate model-scenarios are examined. Results show a significant increase in heat events over the 21st century, with oppressive weather types potentially more than doubling in frequency, and with heat events of 2 weeks or longer becoming up to ten times more common at coastal locations.
  • Authors:
    • Shuman, B.
  • Source: CLIMATIC CHANGE
  • Volume: 112
  • Issue: 2
  • Year: 2012
  • Summary: Wyoming provides more fossil fuels to the remainder of the United States than any other state or country, and its citizens remain skeptical of anthropogenic influences on their climate. However, much of the state including Yellowstone National Park and the headwaters of several major river systems, may have already been affected by rising temperatures. This paper examines the historic climate record from Wyoming in the context of similar to 14,000-year temperature reconstructions based on fossil pollen data. The analysis shows that 24 of 30 U.S. Historical Climatology Network records from the state show an increase in the frequency of unusually warm years since 1978. Statewide temperatures have included 15 years (50%) from 1978 to 2007 that were greater than 1 sigma above the mean annual temperature for 1895-1978. The frequent warm years coincide with a reduction in the frequency of extremely low ( 1A degrees C) is greater than any time in the past 6,000 years. Recent temperatures have become as high as those experienced from 11,000 to 6,000 years ago when summer insolation was > 6% higher than today and when regional ecosystems experienced frequent severe disturbances.
  • Authors:
    • Bosch, D. D.
    • Franklin, D. H.
    • Truman, C. C.
    • Potter, T. L.
    • Strickland, T. C.
    • Hawkins, G. L.
  • Source: SOIL & TILLAGE RESEARCH
  • Volume: 122
  • Year: 2012
  • Summary: Assessment of erosion impact on soil carbon and nitrogen loss and redistribution within landscapes is needed to develop estimates of soil carbon sequestration potential, soil quality management plans, and to evaluate potential for transport of sediment bound agrochemicals. We used variable intensity rainfall simulations to quantify the effects of tillage, conventional and strip, and antecedent soil water content on sediment-bound carbon and nitrogen loss from a Tifton loamy sand located in the southeastern Atlantic Coastal Plain (USA). Carbon and nitrogen loss via erosion of silt. +. clay sized versus sand sized sediment particles were quantified. Antecedent water content had no effect on mean sediment loss within tillage treatments, but losses from conventional till treatments were significantly greater than from strip till. Sediment lost as silt. +. clay was from 58 to 78% of the total under conventional and from 30 to 39% under strip tillage. The fraction of sediment lost as silt. +. clay versus sand was greater under conventional tillage than under strip tillage. Within-event sediment carbon enrichment compared to the top 2. cm of soil was 0.9-7.2 for conventional and 0.6-3.7 for strip tillage. The strip till silt. +. clay fraction had significantly higher carbon content than the strip till sand fraction and the conventional till silt. +. clay fraction. Carbon loss from treatments was directly proportional to sediment loss. However, the conventional till treatments lost 4.6-6 times more carbon from the silt. +. clay sized fraction and 1.9-4.8 times more carbon from the sand sized fraction than strip till treatments. Results suggest that the higher proportion of silt. +. clay fraction sediment loss from conventional till may deplete nitrogen enriched organic matter while decreased erosion from strip till may serve to increase retention of organic nitrogen. Findings also indicate that an approach that adjusts loss estimates of organic carbon and nitrogen by using wet-sieved subsamples for analysis followed by standardization against total bulk sediment loss accounts for introduced errors from both sub-sampling efficiency and disturbance.
  • Authors:
    • Zeckhauser, R. J.
    • Wagner, G.
  • Source: CLIMATIC CHANGE
  • Volume: 110
  • Issue: 3-4
  • Year: 2012
  • Summary: Climate change is more uncertain, more global, and more long-term than most issues facing humanity. This trifecta makes a policy response that encompasses scientific correctness, public awareness, economic efficiency, and governmental effectiveness particularly difficult. Economic and psychological instincts impede rational thought. Elected officials, who cater to and foster voters' misguided beliefs, compound the soft thinking that results. Beliefs must change before unequivocal symptoms appear and humanity experiences the climate-change equivalent of a life-altering heart attack. Sadly, it may well take dramatic loss to jolt the collective conscience toward serious action. In the long run, the only solution is a bottom-up demand leading to policies that appropriately price carbon and technological innovation, and that promote ethical shifts toward a world in which low-carbon, high-efficiency living is the norm. In the short term, however, popular will is unlikely to drive serious action on the issue. Policy makers can and must try to overcome inherent psychological barriers and create pockets of certainty that link benefits of climate policy to local, immediate payoffs. It will take high-level scientific and political leadership to redirect currently misguided market forces toward a positive outcome.
  • Authors:
    • Crosson, E.
    • Bandaru, V.
    • West, T.
    • Andrews, A.
    • Lauvaux, T.
    • Davis, K.
    • Richardson, S.
    • Miles, N.
  • Source: Journal of Geophysical Research-Biogeosciences
  • Volume: 117
  • Issue: G1
  • Year: 2012
  • Summary: This study presents observations of atmospheric boundary layer CO2 mole fraction from a nine-tower regional network deployed during the North American Carbon Program's Mid-Continent Intensive (MCI) during 2007-2009. The MCI region is largely agricultural, with well-documented carbon exchange available via agricultural inventories. By combining vegetation maps and tower footprints, we show the fractional influence of corn, soy, grass, and forest biomes varies widely across the MCI. Differences in the magnitude of CO2 flux from each of these biomes lead to large spatial gradients in the monthly averaged CO2 mole fraction observed in the MCI. In other words, the monthly averaged gradients are tied to regional patterns in net ecosystem exchange (NEE). The daily scale gradients are more weakly connected to regional NEE, instead being governed by local weather and large-scale weather patterns. With this network of tower-based mole fraction measurements, we detect climate-driven interannual changes in crop growth that are confirmed by satellite and inventory methods. These observations show that regional-scale CO2 mole fraction networks yield large, coherent signals governed largely by regional sources and sinks of CO2.
  • Authors:
    • Zegada-Lizarazu, W.
    • Zatta, A.
    • Barbanti, L.
    • Monti, A.
  • Source: Global Change Biology Bioenergy
  • Volume: 4
  • Issue: 4
  • Year: 2012
  • Summary: The contribution of switchgrass (Panicum virgatum L.), a perennial C4 grass, in reducing greenhouse gas (GHG) emissions was reviewed under three main areas; the impact on carbon dioxide (CO2), nitrous oxide (N2O), and methane emissions (CH4), whilst also taking into account the effects of land conversion to switchgrass. Switchgrass is able to enhance biomass accumulation in a wide range of environmental conditions, which is the premise for considerable carbon assimilation and storage in the belowground organs. The progress in some areas of crop husbandry (e.g., tillage and fertilization) has fostered benefits for carbon storage, while restraining GHG emissions. As root biomass is the main indicator of soil carbon sequestration, switchgrass's dense and deep rooting is a relevant advantage, although uncertainty still exists about the crop's belowground biomass accumulation. In agreement with this, most LCA studies addressing CO2 emissions report significant benefits from switchgrass cultivation and processing. Beside CO2, switchgrass performed better than most other biomass crops also in terms of N2O emission. In the case of CH4 emission, it may be argued that switchgrass should act as a moderate sink, i.e., contributing to mitigate CH4 atmospheric concentration, but a substantial lack of information indicates the need for specific research on the topic. Land conversion to switchgrass is the latest issue which needs to be addressed in LCA studies: not surprisingly, the net CO2 abatement appears remarkable if switchgrass is grown in former arable lands, although it is slightly negative to positive if switchgrass replaces permanent grassland. In conclusion, switchgrass could significantly contribute to mitigate GHG emissions, although areas of uncertainty still exist in the assessment of soil carbon storage, N2O and CH4 emissions, and the effects of converting lands to switchgrass. Further improvements must, therefore, be achieved to strengthen the crop's remarkable sustainability.
  • Authors:
    • Bernhardt, E.
    • Ardon, M.
    • Morse, J.
  • Source: Ecological Applications
  • Volume: 22
  • Issue: 1
  • Year: 2012
  • Summary: Whether through sea level rise or wetland restoration, agricultural soils in coastal areas will be inundated at increasing rates, renewing connections to sensitive surface waters and raising critical questions about environmental trade-offs. Wetland restoration is, often implemented in agricultural catchments to improve water quality through nutrient removal. Yet flooding of soils can also increase production of the greenhouse gases nitrous oxide and methane, representing a potential environmental trade-off. Our study aimed to quantify and compare greenhouse gas emissions from unmanaged and restored forested wetlands, as well as actively managed agricultural fields within the North Carolina coastal plain, USA. In sampling conducted once every two months over a two-year comparative study, we found that soil carbon dioxide flux (range: 8000-64 800 kg CO2.ha(-1).yr(-1)) comprised 66-100% of total greenhouse gas emissions from all sites and that methane emissions (range: -6.87 to 197 kg CH4.ha(-1).yr(-1)) were highest from permanently inundated sites, while nitrous oxide fluxes (range: -1.07 to 139 kg N2O.ha(-1).yr(-1)) were highest in sites with lower water tables. Contrary to predictions, greenhouse gas fluxes (as CO2 equivalents) from the restored wetland were lower than from either agricultural fields or unmanaged forested wetlands. In these acidic coastal freshwater ecosystems, the conversion of agricultural fields to flooded young forested wetlands did not result in increases in greenhouse gas emissions.