Quantifying seasonal precipitation using high-resolution carbon isotope analyses in evergreen wood   总被引：1，自引：0，他引：1  

Brian A. Schubert  A. Hope Jahren 《Geochimica et cosmochimica acta》2011,75(22):7291-7303

High-resolution natural abundance stable carbon isotope analyses across annual growth rings in evergreen trees reveal a cyclic increase and decrease in the measured carbon isotopic composition (δ¹³C), but the causes of this pattern are poorly understood. We compiled new and published high-resolution δ¹³C data from across annual growth rings of 33 modern evergreen trees from 10 genera and 15 globally distributed sites to quantify the parameters that affect the observed δ¹³C pattern. Across a broad range of latitude, temperature, and precipitation regimes, we found that the average, measured seasonal change in δ¹³C (Δδ¹³C_meas, ‰) within tree rings of evergreen species reflects changes in the carbon isotopic composition of atmospheric carbon dioxide (Δδ¹³C_CO2) and changes in seasonal precipitation (ΔP) according to the following equation: Δδ¹³C_meas = Δδ¹³C_CO2 - 0.82(ΔP) + 0.73; R² = 0.96. Seasonal changes in temperature, pCO₂, and light levels were not found to significantly affect Δδ¹³C_meas. We propose that this relationship can be used to quantify seasonal patterns in paleoprecipitation from intra-ring profiles of δ¹³C measured from non-permineralized, fossil wood.  相似文献   

Critical issues for the calculation of the social cost of CO2: why the estimates from PAGE09 are higher than those from PAGE2002     

Chris Hope 《Climatic change》2013,117(3):531-543

PAGE09 is an updated version of the PAGE2002 integrated assessment model (Hope 2011a). The default PAGE09 model gives a mean estimate of the social cost of CO₂ (SCCO₂) of $106 per tonne of CO₂, compared to $81 from the PAGE2002 model used in the Stern review (Stern 2007). The increase is the net result of several improvements that have been incorporated into the PAGE09 model in response to the critical debate around the Stern review: the adoption of the A1B socio-economic scenario, rather than A2 whose population assumptions are now thought to be implausible; the use of ranges for the two components of the discount rate, rather than the single values used in the Stern review; a distribution for the climate sensitivity that is consistent with the latest estimates from IPCC 2007a; less adaptation than in PAGE2002, particularly in the economic sector, which was criticised for possibly being over-optimistic; and a more theoretically-justified basis of valuation that gives results appropriate to a representative agent from the focus region, the EU. The effect of each of these adjustments is quantified and explained.  相似文献   

The use of the land-sea warming contrast under climate change to improve impact metrics     

Manoj M. Joshi  Andrew G. Turner  Chris Hope 《Climatic change》2013,117(4):951-960

A favoured method of assimilating information from state-of-the-art climate models into integrated assessment models of climate impacts is to use the transient climate response (TCR) of the climate models as an input, sometimes accompanied by a pattern matching approach to provide spatial information. More recent approaches to the problem use TCR with another independent piece of climate model output: the land-sea surface warming ratio (φ). In this paper we show why the use of φ in addition to TCR has such utility. Multiple linear regressions of surface temperature change onto TCR and φ in 22 climate models from the CMIP3 multi-model database show that the inclusion of φ explains a much greater fraction of the inter-model variance than using TCR alone. The improvement is particularly pronounced in North America and Eurasia in the boreal summer season, and in the Amazon all year round. The use of φ as the second metric is beneficial for three reasons: firstly it is uncorrelated with TCR in state-of-the-art climate models and can therefore be considered as an independent metric; secondly, because of its projected time-invariance, the magnitude of φ is better constrained than TCR in the immediate future; thirdly, the use of two variables is much simpler than approaches such as pattern scaling from climate models. Finally we show how using the latest estimates of φ from climate models with a mean value of 1.6—as opposed to previously reported values of 1.4—can significantly increase the mean time-integrated discounted damage projections in a state-of-the-art integrated assessment model by about 15 %. When compared to damages calculated without the inclusion of the land-sea warming ratio, this figure rises to 65 %, equivalent to almost 200 trillion dollars over 200 years.  相似文献   

THE VEGETATIONAL CHANGES OF THE LAST 20,000 YEARS AT TELEFOMIN, PAPUA NEW GUINEA     

Geoff Hope  MSc.  Ph.D. 《Singapore journal of tropical geography》1983,4(1):25-33

  相似文献   

Staging the Local: rethinking scale in farmers' markets     

Bethaney Turner  Cathy Hope 《The Australian geographer》2015,46(2):147-163

Local food has become a significant focus of food studies analysis in recent years with much of this work identifying the potential environmental, social and economic benefits of food localisation. However, a growing body of literature destabilises these assumed benefits with research now questioning the utility of scale in assessing food system outcomes. This paper explores this destabilisation by examining how concepts associated with the ‘local’ have been deployed by the Capital Region Farmers Market (CRFM) in the Australian Capital Territory (ACT). This leads to two key conclusions: firstly, the practical case study confirms theoretical insights highlighting the instability of the local, identifying how it is animated in multiple and sometimes contradictory ways often in response to conventional market forces; and secondly, we argue that the role of farmers' markets may not be best understood through the lens of the local but, rather, through their role in facilitating citizen engagement with the food system via the direct consumer–producer relationship at markets and the characteristics of the food purchased there (i.e. freshness and quality). In these ways, farmers' markets can disrupt conventional forms of engagement with the food system, creating a space that enhances social embeddedness and which may promote new forms of consumer understanding of food systems.  相似文献   

Policy uncertainty and diffusion of carbon capture and storage in an optimal region     

Chris W. Hope 《Climate Policy》2013,13(5):565-572

Abstract

The social cost of carbon (SCC) is the value of the climate change impacts from 1 tonne of carbon emitted today as CO₂, aggregated over time and discounted back to the present day. We used PAGE2002, the same probabilistic integrated assessment model as used by the Stern Review (Stern et al., 2006), to calculate the SCC and to examine how it varies with discount rate; and find that it is not sensitive to the path of emissions on which the tonne of carbon is superimposed. The mean value of the SCC is $43 per tonne under both a business-as-usual scenario, and under a scenario aimed at stabilizing CO₂ concentrations at 550 ppm. This counter-intuitive result is caused by the interplay between the logarithmic relationship between forcing and concentration, the nonlinear relationship of damage to temperature, and discounting. However, the SCC is sensitive to a number of scientific and economic inputs to the model. Two recent distributions for the sensitivity of climate to a doubling of atmospheric CO₂ (Murphy et al., 2004; Stainforth et al., 2005) increase the mean value of the SCC from $43 to $68 and $90 per tonne. Using a pure rate of time preference of 0.1% per year, as in the Stern Review, gives a mean SCC of $365 per tonne.  相似文献   

The origin of crystalline residues in Stardust Al foils: Surviving cometary dust or crystallized impact melts?     

Penelope J. WOZNIAKIEWICZ  Anton T. KEARSLEY  Hope A. ISHII  Mark J. BURCHELL  John P. BRADLEY  Nick TESLICH  Mike J. COLE  Mark C. PRICE 《Meteoritics & planetary science》2012,47(4):660-670

Abstract– Samples returned by the Stardust mission from comet 81P/Wild 2 provide an unequaled opportunity to investigate cometary formation and evolution. Crystalline silicates have been identified in impact craters in Stardust Al foil, yet their origin is ambiguous. They may be original cometary components, or they may have grown from melt generated by impact. We have now studied experimental impacts of the calcium silicate mineral wollastonite, using scanning and transmission electron microscopy to document the relationship between impact feature shape and crystal lattice orientation in impact residue. Wollastonite can have a characteristic acicular habit, forming crater shapes that indicate crystal orientation upon impact. From extracted impact residue, we determined the lattice orientation of crystalline material for comparison with the whole particle orientation. We assume that crystallization from melt, without surviving seed nuclei, should result in randomly oriented crystallite growth, with no preferred direction for individual crystals. However, we find that the majority of crystalline material in the residue retains b‐axis orientation parallel to the long axis of the crater form. This, together with impact parameter calculations and lack of Al incorporation by the residue (suggesting melting did not occur), indicates that these crystals and, by analogy, the majority of Al‐free crystalline silicates in Stardust foil, are surviving remnants of the impactor. Furthermore, amorphous wollastonite residue probably did not form via melting and subsequent quenching, but instead by high‐pressure amorphization or degradation of unquenchable phases. Finally, one crystal studied appears to be a new high‐pressure/temperature polymorph of CaSiO₃, indicating that such polymorphs may be observed in Stardust residues in craters.  相似文献   

Testing the effects of positional uncertainty on spatial decision‐making     

S. Hope 《International journal of geographical information science》2013,27(6):645-665

There is now increasing agreement that the uncertainty associated with spatial information should be represented to users in a manner that is comprehensive and unambiguous. To assist with this task, researchers have developed a variety of methods to portray spatial uncertainty. While there has been some testing of the effectiveness of these displays, the possible effects of such representations on decision‐making have not yet been thoroughly investigated. Indeed, studies from the psychological literature indicate that people do not always make the same decisions when presented with the same information, and they can also be sensitive to the effects of presentation, task, and context. This paper examines how the use of four different methods to represent positional uncertainty can affect spatial decision‐making. The authors found that extremely significant differences in participants' responses were exhibited, depending on the manner in which positional uncertainty was displayed, although little difference was observed in the ability of the participants to comprehend the four display methods. In addition, strong preferences were recorded for certain representations over others.  相似文献   

Vertical distribution of living mangrove foraminifera from KwaZulu-Natal,South Africa     

KL Strachan  TR Hill  JM Finch 《African Journal of Marine Science》2017,39(4):409-422

Modern foraminiferal assemblage zones can be used to reconstruct palaeo sea levels when applied to fossil foraminifera down a sediment core. Previous intertidal foraminiferal studies have predominantly focused on assemblages in surface sediments (0–1 cm), with the rationale that surface assemblages reflect the modern-day environment. Foraminifera live infaunally and therefore there is a need to document the infaunal vertical distribution of living foraminifera to fully capture the modern environment. Infaunal foraminiferal populations may compositionally differ from or be similar to those in the uppermost 1 cm of a core sample, but abundance is variable vertically, making it very complex to reconstruct and interpret past sea levels. This can have implications for the choice of assemblages to use as modern analogues for past sea-level reconstructions. This study documents the vertical infaunal distribution of living foraminifera, to allow for more informed interpretations of palaeo-reconstructions in mangrove environments. The down-core vertical distribution and abundance of living foraminifera, along with grain size and organic content, were documented using sediment cores along an elevational transect. Nine taxa were recorded as living at the time of collection, six of which were restricted to the top 4 cm. The majority of these were calcareous and found in the cores situated closer to the intertidal channel. Therefore, we argue that the diversity of living calcareous and agglutinated foraminifera could be restricted by grain size, with coarser grain sizes associated with lower species diversity. The findings suggest that foraminiferal species inhabiting the top 4 cm represent deeper living foraminiferal populations. Therefore, the top 4-cm interval can be used to establish a modern training set upon which reconstructions can be based. The findings from this study will provide guidance on the use of South African mangrove environments for future sea-level reconstructions.  相似文献   

National Inventories of Terrestrial Carbon Sources and Sinks: The U.K. Experience   总被引：1，自引：0，他引：1  

M. G. R. Cannell  R. Milne  K. J. Hargreaves  T. A. W. Brown  M. M. Cruickshank  R. I. Bradley  T. Spencer  D. Hope  M. F. Billett  W. N. Adger  S. Subak 《Climatic change》1999,42(3):505-530

The U.K. has extensive databases on soils, land cover and historic land use change which have made it possible to construct a comprehensive inventory of the principal terrestrial sources and sinks of carbon for approximately the year 1990, using methods that are consistent with, and at least as accurate as, the revised 1996 guidelines recommended by IPCC where available – and including categories which are not currently considered under the UN Framework Convention on Climate Change. This country inventory highlights issues concerning methodology, uncertainty, double counting, the importance of soils and the relative magnitude of sources and sinks which are reported to the UNFCCC relative to other sources and sinks. The carbon sinks (negative values in MtC a^-1) for categories reported to the UNFCCC, based on the IPCC categories, were estimated to be: forest trees and litter (–2.1), U.K. forest products (–0.5, ignoring imports and exports), non-forest biomass (–0.3), forest soils (–0.1) and soils on set-aside land (–0.4). The carbon sources (positive values) reported under the UNFCCC were estimated to be: losses of soil organic carbon resulting from cultivation of semi-natural land (6.2) and from urbanization (1.6), drainage of peatlands (0.3) and fenlands (0.5), and peat extraction (0.2). A range of other sources and sinks not covered by the IPCC guidelines were also quantified, namely, the accumulation of carbon in undrained peatlands (–0.7, ignoring methane emission), sediment accretion in coastal marshes (–0.1), the possible U.K. share of the CO₂ and N fertilization carbon sink (–2.0) and riverine organic and particulate carbon export to the sea (1.4, which may be assumed to be a source if most of this carbon is released as CO₂ in the sea). All sinks totalled –6.2 and sources 10.2, giving a net flux to the atmosphere in 1990 of 4.0 MtC a^-1. Uncertainties associated with categories, mostly based on best guesses, ranged from ±15% for forest biomass and litter to ±60% for CO₂ and N fertilization.  相似文献