What do near-term observations tell us about long-term developments in greenhouse gas emissions?     

Detlef P. van Vuuren  Jae Edmonds  Steven J. Smith  Kate V. Calvin  Joseph Karas  Mikiko Kainuma  Nebojsa Nakicenovic  Keywan Riahi  Bas J. van Ruijven  Rob Swart  Allison Thomson 《Climatic change》2010,103(3-4):635-642

Long-term scenarios developed by integrated assessment models are used in climate research to provide an indication of plausible long-term emissions of greenhouse gases and other radiatively active substances based on developments in the global energy system, land-use and the emissions associated with these systems. The phenomena that determine these long-term developments (several decades or even centuries) are very different than those that operate on a shorter time-scales (a few years). Nevertheless, in the literature, we still often find direct comparisons between short-term observations and long-term developments that do not take into account the differing dynamics over these time scales. In this letter, we discuss some of the differences between the factors that operate in the short term and those that operate in the long term. We use long-term historical emissions trends to show that short-term observations are very poor indicators of long-term future emissions developments. Based on this, we conclude that the performance of long-term scenarios should be evaluated against the appropriate, corresponding long-term variables and trends. The research community may facilitate this by developing appropriate data sets and protocols that can be used to test the performance of long-term scenarios and the models that produce them.  相似文献   

Accurate extragalactic distances and dark energy: anchoring the distance scale with rotational parallaxes     

Rob P. Olling 《Monthly notices of the Royal Astronomical Society》2007,378(4):1385-1399

  相似文献   

Fitness spaces and their potential for visualizing change in the physical landscape     

Rob Inkpen  & Dave Petley 《Area》2001,33(3):242-251

The use of the metaphors of general fitness and N-K spaces can assist in the understanding of the development of the physical landscape. Different modes of change can be viewed as different types of movement in, and distortions of, these phase spaces. Visualized in this manner landscape change can be viewed as both channelized, constrained and random.  相似文献   

Turbulent flow structure in a gravel-bed river: Markov chain analysis of the fluctuating velocity profile     

Alistair D. Kirkbride  Rob Ferguson 《地球表面变化过程与地形》1995,20(8):721-733

Three electromagnetic current meter probes were deployed in a Canadian gravel-bed river to obtain simultaneous records at 10 Hz of streamwise (u) and vertical (v) velocity components at three heights above the bed. By looking at the positive and negative signs of the instantaneous fluctuations from the time-average values of each velocity component at each height, the fluctuating velocity profile of u or v can be treated as a Markov chain with eight states and its statistical properties can be tested against null hypotheses based on the absence of spatial structure. We report results of this novel approach. The most common states of the u profile were those with either higher-than-average or lower-than-average velocities at all heights; these ‘high speed’ and ‘low speed’ states persisted for up to 3 s. The most common v profiles were all-upwards or all-downwards, but these persisted for shorter times than the high speed and low speed u profiles. Analysis of transition probabilities shows statistically significant tendencies for acceleration from the low speed u profile, and change from all-upwards to all-downwards v profile, to take place progressively from the uppermost probe downwards, in a sweep-like way. Deceleration from the high speed to low speed u profile and change from all-downwards to all-upwards v profile (burst-like behaviour) do not show such clear patterns. The results are interpreted in terms of the advection of inverted wedges of relatively high-momentum fluid, followed by more chaotic structures. A separate set of flow visualization experiments over a mixed gravel bed in a flume supports the presence of advected wedge structures, the decelerating part of the sequence corresponding to irregular ejections of near-bed fluid.  相似文献   

Errors in measuring the percentage dry weight change of stone tablets     

Rob Inkpen 《地球表面变化过程与地形》1995,20(9):783-793

Portland Stone and Monks Park limestone tablets were used to assess weathering loss over a two-year study. Procedures involved in preparing tablets for exposure, attaching them to the exposure frame and reweighing might have influenced weight changes measured. The impact of each stage in the above procedures was tested to assess how much weight loss was generated and how significant the loss was comparing the two stone types and the final loss sustained upon weathering. Although all the procedures seem to produce a statistically insignificant amount of weight loss, the two stone types do respond differently to the procedures. This suggests that stone properties may be important in determining the accuracy with which tablets can be used to assess spatial patterns of weathering.  相似文献   

Upper-mantle shear velocity beneath eastern Australia from inversion of waveforms from SKIPPY portable arrays   总被引：2，自引：0，他引：2  

Alet Zielhuis  Rob D. van der  Hilst 《Geophysical Journal International》1996,127(1):1-16

  相似文献   

Undications of current action in late Jurassic limestones,radiolarian limestones,saccocoma limestones and associated rocks from the subbetic of SE Spain     

B. Kuhry  S.W.G. De Clercq  L. Dekker 《Sedimentary Geology》1976,15(3):235-258

In the Vélez Blanco region (province of Almeia), filament limestones occur associated with pellet limestones, crinoidal limestones, radiolarian limestones, Saccocoma limestones and tintinnid limestones. These predominantly Late Jurassic rocks are underlain by Middle Jurassic oolitic limestones and overlain by Cretaceous pelagic limestones and marls.A distinction can be made between long and short filaments. The former are interpreted as undamaged valves, the latter as shell fragments of the pelagic pelecypod Bositra buchi. Bositra valves and fragments have been sorted by weak current (and/or wave) action.In the Saccocoma limestones, evidence for similar sorting of Saccocoma debris has been found.The radiolarian limestones represent a low-energy basin environment, but are not comparable with recent deep-sea radiolarian oozes.Nodular limestone intercalations and hiatuses represent a current- (and/or wave-) swept environment.The occurrence of filament-rich and Radiolaria-bearing, but benthos-poor, intervals within the oolitic limestone indicates that the deposition of such rocks can take place at moderate sea depths.  相似文献   

Paleomagnetism of the triassic chugwater redbeds revisited (Wyoming, U.S.A.)     

Rob Van Der Voo  Ken L. Grubbs   《Tectonophysics》1977,41(4):T27-T33

Paleomagnetic results from 107 samples of the Chugwater Group near Lander, Wyoming, show a regular progression in pole positions from bottom to top of the sequence. This pole position trend of about 25° matches very well the North American apparent polar wander path between Early Permian and Early Triassic. It could be argued that this “agreement” results in a conflict between the apparent magnetic age (Permian) and the Early to Late Triassic age generally assigned to the Chugwater Group. However, similar progressions of paleomagnetic pole positions have been reported for the Early Triassic Moenkopi Formation in Colorado; thus it appears that long-term variations and swings characterized the geomagnetic field at that time. With detailed paleomagnetic sampling, these features can be utilized for stratigraphic correlation in addition to magnetic-reversal stratigraphy. This will eliminate, to some degree, part of the non-uniqueness inherently present in correlations based on reversal stratigraphy only.  相似文献   

Paleomagnetic and rock magnetic results from the Twin Creek Formation (Middle Jurassic), Wyoming     

Chad McCabe  Rob Van der Voo  Bruce H. Wilkinson 《Earth and Planetary Science Letters》1982,60(1):140-146

A magnetization which passes the fold test has been observed in 73 limestone samples (10 sites) from the Middle Jurassic Twin Creek Formation. The pole calculated from the site mean poles is located at 68.4°N, 145.0°E (K = 31.8,A₉₅ = 8.7°). This pole lies in a segment of the North American apparent polar wander (APW) path for which there are only a few reliable poles in the literature. The results corroborate earlier studies which conclude that the Jurassic segment of the APW path does not include the present north pole. However, the position of the Twin Creek pole suggests that significantly more APW took place prior to the late Jurassic than previous studies indicated.  相似文献   

Perception of urban retailing environments: An empirical analysis of consumer information and usage fields     

Harry Timmermans  Rob Van Der Heijden  Hans Westerveld 《Geoforum》1982,13(1):27-37

This article reports on an empirical analysis of consumer information and usage fields in the city of Eindhoven. The main purposes of this study are to investigate the distance, sectoral and directional biases of these fields, to analyse whether the degree of biases is related to personal characteristics of consumers and to identify the factors of the basis on which a model which predicts the probability that a shopping centre will be known by consumers can be developed. The findings of the study suggest that strong distance, sectoral and directional biases are present in the information and usage fields of consumers and that no systematic relationships exist between these characteristics of information and usage fields and personal variables of consumers. Finally, the present studies suggests that a model which describes the formation of consumer choice sets should include spatial factors such as distance, size, intervening opportunities and direction towards the city centre.  相似文献