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Terrestrial water fluxes dominated by transpiration
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Renewable fresh water over continents has input from precipitation and losses to the atmosphere through evaporation and transpiration .... The dominance of transpiration water fluxes in continental evapotranspiration suggests that, from the point of view of water resource forecasting, climate model development should prioritize improvements in simulations of biological fluxes rather than physical (evaporation) fluxes.
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The 2 °C dream
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Countries have pledged to limit global warming to 2 °C, and climate models say that is still possible. But only with heroic — and unlikely — efforts.
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The cold-water climate shield: delineating refugia for preserving salmonid fishes through the 21st century
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The distribution and future fate of ectothermic organisms in a warming world will be dictated by thermal-scapes across landscapes. That is particularly true for stream fishes and cold-water species like trout, salmon, and char that are already constrained to high elevations and latitudes. The extreme climates in those environments also preclude invasions by most non-native species, so identifying especially cold habitats capable of absorbing future climate change while still supporting native populations would highlight important refugia. By coupling crowd-sourced biological datasets with high-resolution stream temperature scenarios, we delineate network refugia across >250 000 stream km in the Northern Rocky Mountains for two native salmonids—bull trout (BT) and cutthroat trout (CT). Under both moderate and extreme climate change scenarios, refugia with high probabilities of trout population occupancy (>0.9) were predicted to exist (33–68 BT refugia; 917–1425 CT refugia). Most refugia are on public lands (>90%) where few currently have protected status in National Parks or Wilderness Areas (<15%). Forecasts of refuge locations could enable protection of key watersheds and provide a foundation for climate smart planning of conservation networks. Using cold water as a ‘climate shield’ is generalizable to other species and geographic areas because it has a strong physiological basis, relies on nationally available geospatial data, and mines existing biological datasets.
Importantly, the approach creates a framework to integrate data contributed by many individuals and resource agencies, and a process that strengthens the collaborative and social networks needed to preserve many cold-water fish populations through the 21st century.
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THE COST OF INACTION: RECOGNISING THE VALUE AT RISK FROM CLIMATE CHANGE
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The asset management industry—and thus the wider community of investors of all sizes— is facing the prospect of significant losses from the effects of climate change. Assets can be directly damaged by floods, droughts and severe storms, but portfolios can also be harmed indirectly, through weaker growth and lower asset returns. Climate change is a long-term, probably irreversible problem beset by substantial uncertainty. Crucially, however, climate change is a problem of extreme risk: this means that the average losses to be expected are not the only source of concern; on the contrary, the outliers, the particularly extreme scenarios, may matter most of all.
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The declining uptake rate of atmospheric CO2 by land and ocean sinks
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Through 1959–2012, an airborne fraction (AF) of 0.44 of total anthropogenic CO2 emissions remained in the atmosphere, with the rest being taken up by land and ocean CO2 sinks. Understanding of this uptake is critical because it greatly alleviates the emissions reductions required for climate mitigation, and also reduces the risks and damages that adaptation has to embrace. An observable quantity that reflects sink properties more directly than the AF is the CO2 sink rate (kS), the combined land–ocean CO2 sink flux per unit excess atmospheric CO2 above preindustrial levels. Here we show from observations that kS declined over 1959–2012 by a factor of about 1/3, implying that CO2 sinks increased more slowly than excess CO2. Us- ing a carbon–climate model, we attribute the decline in kS to four mechanisms: slower-than-exponential CO2 emissions growth (∼ 35 % of the trend), volcanic eruptions (∼ 25 %), sink responses to climate change (∼ 20 %), and nonlinear responses to increasing CO2, mainly oceanic (∼ 20 %). The first of these mechanisms is associated purely with the trajectory of extrinsic forcing, and the last two with intrinsic, feedback responses of sink processes to changes in climate and atmospheric CO2. Our results suggest that the effects of these intrinsic, nonlinear responses are already detectable in the global carbon cycle. Although continuing future decreases in kS will occur under all plausible CO2 emission scenarios, the rate of decline varies between scenarios in non- intuitive ways because extrinsic and intrinsic mechanisms respond in opposite ways to changes in emissions: extrinsic mechanisms cause kS to decline more strongly with increasing mitigation, while intrinsic mechanisms cause kS to decline more strongly under high-emission, low-mitigation scenarios as the carbon–climate system is perturbed further from a near-linear regime.
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The future of farming: return to roots?
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Large scale farming would be more sustainable if major crop plants lived for years and built deep root systems.
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The global volume and distribution of modern groundwater
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Groundwater is important for energy and food security, human health and ecosystems. The time since groundwater was recharged—or groundwater age—can be important for diverse geologic processes, such as chemical weathering, ocean eutrophication and climate change. However, measured groundwater ages range from months to millions of years. The global volume and distribution of groundwater less than 50 years old—modern groundwater that is the most recently recharged and also the most vulnerable to global change—are unknown. Here we combine geochemical, geologic, hydrologic and geospatial data sets with numerical simulations of groundwater and analyse tritium ages to show that less than 6% of the groundwater in the uppermost portion of Earth’s landmass is modern. We find that the total groundwater volume in the upper 2 km of continental crust is approximately 22.6 million km3 , of which 0.1–5.0 million km3 is less than 50 years old. Although modern groundwater represents a small percentage of the total groundwater on Earth, the volume of modern groundwater is equivalent to a body of water with a depth of about 3 m spread over the continents. This water resource dwarfs all other components of the active hydrologic cycle.
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The global volume and distribution of modern groundwater
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Groundwater is important for energy and food security, human health and ecosystems. The time since groundwater was recharged—or groundwater age—can be important for diverse geologic processes, such as chemical weathering, ocean eutrophication and climate change. However, measured groundwater ages range from months to millions of years. The global volume and distribution of groundwater less than 50 years old—modern groundwater that is the most recently recharged and also the most vulnerable to global change—are unknown. Here we combine geochemical, geologic, hydrologic and geospatial data sets with numerical simulations of groundwater and analyse tritium ages to show that less than 6% of the groundwater in the uppermost portion of Earth’s landmass is modern. We find that the total groundwater volume in the upper 2 km of continental crust is approximately 22.6 million km3 , of which 0.1–5.0 million km3 is less than 50 years old. Although modern groundwater represents a small percentage of the total groundwater on Earth, the volume of modern groundwater is equivalent to a body of water with a depth of about 3 m spread over the continents. This water resource dwarfs all other components of the active hydrologic cycle.
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The Historical Dynamics of Social–Ecological Traps
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Environmental degradation is a typical unintended outcome of collective human behavior. Hardin’s metaphor of the ‘‘tragedy of the commons’’ has become a conceived wisdom that captures the social dynamics leading to environmental degradation. Recently, ‘‘traps’’ has gained currency as an alternative concept to explain the rigidity of social and ecological processes that produce environmental degradation and livelihood impoverishment. The trap metaphor is, however, a great deal more complex compared to Hardin’s insight. This paper takes stock of studies using the trap metaphor. It argues that the concept includes time and history in the analysis, but only as background conditions and not as a factor of causality. From a historical–sociological perspective this is remarkable since social–ecological traps are clearly path-dependent processes, which are causally produced through a conjunction of events. To prove this point the paper conceptualizes social–ecological traps as a process instead of a condition, and systematically compares history and timing in one classic and three recent studies of social– ecological traps. Based on this comparison it concludes that conjunction of social and environmental events contributes profoundly to the production of trap processes. The paper further discusses the implications of this conclusion for policy intervention and outlines how future research might generalize insights from historical–sociological studies of traps.
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The influence of contextual cues on the perceived status of consumption-reducing behavior
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The question of whether and when behaviors that reduce overall consumption are associated with low status has not been adequately explored. Previous research suggests that some low cost environmentally-friendly behaviors are stigmatized, but has not accounted for the impact of contextual information on perceived status. Here, we use costly signaling theory to describe why consumption-reducing behaviors may be associated with low status and when and how this perception might change. We report two empirical studies in the U.S. that use a large sample of graduate students (N = 447) to examine the effects of contextual information on how consumption-reducing behaviors are perceived. We then explore the perceived appropriateness of consumption-reducing behavior for signaling status relative to alternative non-environmental behaviors. Using linear mixed-effects models, we find that information indicating that consumption-reducing behavior is a choice results in higher perceived status. However, we find that consumption-reducing behaviors are perceived to be less appropriate for conveying status than consumption-intensive behaviors. The environmental orientation of the respondent has little effect on perceptions of status in both studies. These results provide insights into the dynamic, evolutionary process by which sustainable consumption might become more socially acceptable and the social factors that may inhibit this process.
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