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[en] Caribbean tropical forests are subject to hurricane disturbances of great variability. In addition to natural storm incongruity, climate change can alter storm formation, duration, frequency, and intensity. This model -based investigation assessed the impacts of multiple storms of different intensities and occurrence frequencies on the long-term dynamics of subtropical dry forests in Puerto Rico. Using the previously validated individual-based gap model ZELIG-TROP, we developed a new hurricane damage routine and parameterized it with site- and species-specific hurricane effects. A baseline case with the reconstructed historical hurricane regime represented the control condition. Ten treatment cases, reflecting plausible shifts in hurricane regimes, manipulated both hurricane return time (i.e. frequency) and hurricane intensity. The treatment-related change in carbon storage and fluxes were reported as changes in aboveground forest biomass (AGB), net primary productivity (NPP), and in the aboveground carbon partitioning components, or annual carbon accumulation (ACA). Increasing the frequency of hurricanes decreased aboveground biomass by between 5% and 39%, and increased NPP between 32% and 50%. Decadal-scale biomass fluctuations were damped relative to the control. In contrast, increasing hurricane intensity did not create a large shift in the long-term average forest structure, NPP, or ACA from that of historical hurricane regimes, but produced large fluctuations in biomass. Decreasing both the hurricane intensity and frequency by 50% produced the highest values of biomass and NPP. For the control scenario and with increased hurricane intensity, ACA was negative, which indicated that the aboveground forest components acted as a carbon source. However, with an increase in the frequency of storms or decreased storms, the total ACA was positive due to shifts in leaf production, annual litterfall, and coarse woody debris inputs, indicating a carbon sink into the forest over the long-term. The carbon loss from each hurricane event, in all scenarios, always recovered over sufficient time. Our results suggest that subtropical dry forests will remain resilient to hurricane disturbance. However carbon stocks will decrease if future climates increase hurricane frequency by 50% or more.
[en] In this study, renewable portfolio standards (RPS) exist in 29 US states and the District of Columbia. This article summarizes the first national-level, integrated assessment of the future costs and benefits of existing RPS policies; the same metrics are evaluated under a second scenario in which widespread expansion of these policies is assumed to occur. Depending on assumptions about renewable energy technology advancement and natural gas prices, existing RPS policies increase electric system costs by as much as 31 billion dollars, on a present-value basis over 2015-2050. The expanded renewable deployment scenario yields incremental costs that range from 23 billion to 194 billion dollars, depending on the assumptions employed. The monetized value of improved air quality and reduced climate damages exceed these costs. Using central assumptions, existing RPS policies yield 97 billion dollars in air-pollution health benefits and 161 billion dollars in climate damage reductions. Under the expanded RPS case, health benefits total 558 billion dollars and climate benefits equal 599 billion dollars. These scenarios also yield benefits in the form of reduced water use. RPS programs are not likely to represent the most cost effective path towards achieving air quality and climate benefits. Nonetheless, the findings suggest that US RPS programs are, on a national basis, cost effective when considering externalities.
[en] Since the United States began a program to develop ethanol as a transportation fuel, its use has increased from 175 million gallons in 1980 to 4.9 billion gallons in 2006. Virtually all of the ethanol used for transportation has been produced from corn. During the period of fuel ethanol growth, corn farming productivity has increased dramatically, and energy use in ethanol plants has been reduced by almost by half. The majority of corn ethanol plants are powered by natural gas. However, as natural gas prices have skyrocketed over the last several years, efforts have been made to further reduce the energy used in ethanol plants or to switch from natural gas to other fuels, such as coal and wood chips. In this paper, we examine nine corn ethanol plant types--categorized according to the type of process fuels employed, use of combined heat and power, and production of wet distiller grains and solubles. We found that these ethanol plant types can have distinctly different energy and greenhouse gas emission effects on a full fuel-cycle basis. In particular, greenhouse gas emission impacts can vary significantly--from a 3% increase if coal is the process fuel to a 52% reduction if wood chips are used. Our results show that, in order to achieve energy and greenhouse gas emission benefits, researchers need to closely examine and differentiate among the types of plants used to produce corn ethanol so that corn ethanol production would move towards a more sustainable path
[en] Sillman et al (2014) find that observed trends of extremely hot days and cold nights are consistent with the current generation of climate models. Short periods of localized decreases in these extreme temperatures are not unusual and the Sillman et al results increase confidence in projections of future changes in extreme temperature.
[en] Thermal pollution from power plants degrades riverine ecosystems with ramifications beyond the natural environment as it affects power supply. The transport of thermal effluents along river reaches may lead to plant-to-plant interferences by elevating condenser inlet temperatures at downstream locations, which lower thermal efficiencies and trigger regulatory-forced power curtailments. We evaluate thermal pollution impacts on rivers and power supply across 128 plants with once-through cooling technologies in the Mississippi River watershed. By leveraging river network topologies with higher resolutions (0.05 degrees) than previous studies, we reveal the need to address the issue in a more spatially resolved manner, capable of uncovering diverse impacts across individual plants, river reaches and sub-basins. Results show that the use of coarse river network resolutions may lead to substantial overestimations in magnitude and length of impaired river reaches. Overall, there is a modest limitation on power production due to thermal pollution, given existing infrastructure, regulatory and climate conditions. However, tradeoffs between thermal pollution and electricity generation show important implications for the role of alternative cooling technologies and environmental regulation under current and future climates. Recirculating cooling technologies may nearly eliminate thermal pollution and improve power system reliability under stressed climate-water conditions. Regulatory limits also reduce thermal pollution, but at the expense of significant reductions in electricity generation capacity. However, results show several instances when power production capacity rises at individual plants when regulatory limits reduce upstream thermal pollution. Furthermore, these dynamics across energy-water systems highlight the need for high-resolution simulations and the value of coherent planning and optimization across infrastructure with mutual dependencies on natural resources to overcome climate-water constraints on productivity and bring to fruition energy and environmental win-win opportunities.
[en] Increasing atmospheric methane (CH4) concentrations have contributed to approximately 20% of anthropogenic climate change. Despite the importance of CH4 as a greenhouse gas, its atmospheric growth rate and dynamics over the past two decades, which include a stabilization period (1999–2006), followed by renewed growth starting in 2007, remain poorly understood. We provide an updated estimate of CH4 emissions from wetlands, the largest natural global CH4 source, for 2000–2012 using an ensemble of biogeochemical models constrained with remote sensing surface inundation and inventory-based wetland area data. Between 2000–2012, boreal wetland CH4 emissions increased by 1.2 Tg yr–1 (–0.2–3.5 Tg yr–1), tropical emissions decreased by 0.9 Tg yr–1 (–3.2–1.1 Tg yr–1), yet globally, emissions remained unchanged at 184 ± 22 Tg yr–1. Changing air temperature was responsible for increasing high-latitude emissions whereas declines in low-latitude wetland area decreased tropical emissions; both dynamics are consistent with features of predicted centennial-scale climate change impacts on wetland CH4 emissions. Despite uncertainties in wetland area mapping, our study shows that global wetland CH4 emissions have not contributed significantly to the period of renewed atmospheric CH4 growth, and is consistent with findings from studies that indicate some combination of increasing fossil fuel and agriculture-related CH4 emissions, and a decrease in the atmospheric oxidative sink.
[en] China has become the world's second largest greenhouse gas (GHG) emitter behind the United States. It emits approximately three billion tons of CO2 equivalents every year. Its growing economy and large population are making a wealthier, more consumption-oriented country. Energy demand is expected to grow 5-10% per year through 2030. Therefore, a large potential of GHG emission reduction in China can be expected. The clean development mechanism (CDM) put forward in the Kyoto Protocol for reductions of GHGs can support the sustainable development of developing countries and help developed countries to achieve their emission reduction targets at low cost. However, there are still many disagreements to be resolved between developing and developed countries. In this letter, we try to introduce the current development of CDM projects in China and discuss its potential and opportunities in the future decades
[en] Higher energy prices and concern about climate change is drawing increasing attention to ground source heat pump (GSHP) systems. Their clear advantage lies in being able to provide heating using 25 to 30% of the energy consumed by even the most efficient conventional alternatives. Their drawback has been high capital costs and uncertainty about whether the emissions associated with the electric power used to energise the system has higher system-wide emissions than the highest-efficiency furnaces. This study delineates circumstances under which GSHP systems achieve net emission reductions, for different electricity generation methods, heat pump efficiencies, and heating loads. We illustrate the effect of relative fuel prices on annual operating savings using fuel prices in multiple countries. Annual operating savings determine how rapidly the technology achieves payback and then generates return on the initial capital investment. Finally, we highlight the least cost supply curve for using GSHP to reduce greenhouse gas emissions. Using the United States as a base reference case, this study explores the potential of GSHP in cold-climate countries worldwide
[en] Many small groups of indigenous peoples in the Amazon basin avoid and resist direct encounters with outsiders. As far as we know, they do so because of appalling experiences in earlier encounters with national society. When contacted today, they are extremely vulnerable to introduced diseases and exploitation. In this paper we draw on our experience in the Kugapakori Nahua Reserve for isolated peoples in SE Peru to discuss some of the current debates about whether isolated peoples should be contacted and how best to respect their right to life, health, autonomy and territory. The remote headwater regions where isolated peoples sought refuge during the last century are increasingly sought after for resource extraction. In particular, the extraction of oil and gas is increasing throughout the Peruvian Amazon. In the second part of the paper we give some examples of how oil/gas companies and the energy sector in Peru have affected the well-being of the peoples in this reserve in the 21st century. If this trend is not reversed the impacts for isolated peoples will be irreparable
[en] Health socioeconomic gradients are well documented in developed countries, but incompletely explained. A portion of these health inequalities may be explained by environmental exposures. The objective of PAISARC is to explore the relations between socioeconomic status, air pollution exposure and two selected health outcomes-asthma exacerbations and myocardial infarction-at the level of a small area. The study design is ecological, using data available from the national census, with the residential block (French IRIS, 2000 people on average, National Institute of Statistics-INSEE) as the statistical unit. The setting is the Greater Strasbourg metropolitan area (450 000 inhabitants) in eastern France. We first constructed a socioeconomic status index, using 1999 national census data and principal component analysis at the resolution of these census blocks. Air pollution data were then modeled at the same resolution on an hourly basis for the entire study period (2000-2005). Health data were obtained from various sources (local emergency networks, the local population-based coronary heart disease registry, health insurance funds) according to the health outcome. We present here the initial results and discuss the methodological approaches best suited for the forthcoming steps of our project