Reflections on the current state of global climate response     

Tom Jacob 《Climate Policy》2013,13(1):91-97

What is the significance of the 2007 United Nations Climate Change Conference in Bali? The formal outcomes, especially the ‘Bali Action Plan’, are described and commented on, along with the challenges for negotiating a post-2012 agreement in Copenhagen during 2008 and 2009. The article concludes that the outcome of the Bali meeting is insufficient when compared to the nature of the challenge posed by climate change. However, it can nevertheless be considered a success in terms of ‘Realpolitik’ in paving the way for the negotiations ahead, because some real changes have been discerned in the political landscape. The challenges for the road towards Copenhagen are manifold: the sheer volume and complexity of the issues and the far-reaching nature of decisions such as differentiation between non- Annex I countries pose significant challenges in themselves, while the dependency on the electoral process in the USA introduces a high element of risk into the whole process. The emergence of social justice as an issue turns climate policy into an endeavour to improve the world at large—thereby adding to the complexity. And, finally, the biggest challenge is the recognition that the climate problem requires a global solution, that Annex I and non-Annex I countries are mutually dependent on each other and that only cooperation regarding technology in combination with significant financial support will provide the chance to successfully tackle climate change.  相似文献   

Multiwavelength diameters of nearby Miras and semiregular variables     

M. J. Ireland  P. G. Tuthill  T. R. Bedding  J. G. Robertson  A. P. Jacob 《Monthly notices of the Royal Astronomical Society》2004,350(1):365-374

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Anharmonicity effects in bounce motion of particles     

Jacob Sundara Raja 《Planetary and Space Science》2006,54(1):113-116

Equations for parallel motion for a particle trapped in a magnetic field have been considered and improved solutions of differential equations have been derived. The expressions for the change in energy of the particle (Δw) and diffusion coefficient (D_ww) have been presented in a simple form using the improved solution.  相似文献   

On the shape of the non-steady interface intersecting discontinuities in permeability     

Jacob Bear  Allen M. Shapiro 《Advances in water resources》1984,7(3):106-112

The simplifying assumption is often made, that when two fluids (whether miscible or immiscible) occupy the void space of a porous medium, they are separated by a sharp interface. Examples are the phreatic surface (between air and water) and the interface between fresh and salt water in a coastal aquifer. The orientation of such a sharp interface as it crosses a surface of discontinuity between media of different permeabilities, and as it intersects an impervious boundary, is shown to depend not only on the fluid and porous media properties, but also on the direction and rate of motion of the interface. Thus, advancing and retreating interfaces intersect boundaries of discontinuity in permeability at different angles.  相似文献   

The dispersive flux in transport phenomena in porous media     

Yehuda Bachmat  Jacob Bear 《Advances in water resources》1983,6(3):169-174

Employing the principles of continuum mechanics and a volumetric averaging approach to the derivation of the macroscopic balance equation of an extensive quantity of a fluid phase in a porous medium, the paper derives a macroscopic expression for the dispersive flux that appears in the latter as a result of averaging. It is shown that the dispersive flux obeys a Fickian type law, i.e., it is proportional to the macroscopic density gradient of the considered extensive quantity. The nature of the coefficient of dispersion that appears in the expression of the dispersive flux is analyzed and interpreted.  相似文献   

On the aquifer's integrated balance equations     

Jacob Bear 《Advances in water resources》1977,1(1):15-23

A general methodology is presented for describing transport phenomena in porous media at a macroscopic level. Then, these macroscopic balance equations are integrated (or averaged) along the vertical for confined, leaky and phreatic aquifers.The results are employed to derive (averaged) aquifer equations for the flow of water and of a solute (hydrodynamic dispersion). It is shown that in all cases, the resulting equation is identical to that derived on the basis of an assumption of horizontal flow (the Dupuit assumption).Macrodispersion, occurring at the aquifer level, is discussed and appropriate coefficients are proposed.  相似文献   

Evaluation of an ensemble of Arctic regional climate models: spatiotemporal fields during the SHEBA year   总被引：1，自引：1，他引：0  

A.?RinkeEmail author  K.?Dethloff  J.?J.?Cassano  J.?H.?Christensen  J.?A.?Curry  P.?Du  E.?Girard  J.-E.?Haugen  D.?Jacob  C.?G.?Jones  M.?K?ltzow  R.?Laprise  A.H.?Lynch  S.?Pfeifer  M.?C.?Serreze  M.?J.?Shaw  M.?Tjernstr?m  K.?Wyser  M.??agar 《Climate Dynamics》2006,26(5):459-472

Simulations of eight different regional climate models (RCMs) have been performed for the period September 1997–September 1998, which coincides with the Surface Heat Budget of the Arctic Ocean (SHEBA) project period. Each of the models employed approximately the same domain covering the western Arctic, the same horizontal resolution of 50 km, and the same boundary forcing. The models differ in their vertical resolution as well as in the treatments of dynamics and physical parameterizations. Both the common features and differences of the simulated spatiotemporal patterns of geopotential, temperature, cloud cover, and long-/shortwave downward radiation between the individual model simulations are investigated. With this work, we quantify the scatter among the models and therefore the magnitude of disagreement and unreliability of current Arctic RCM simulations. Even with the relatively constrained experimental design we notice a considerable scatter among the different RCMs. We found the largest across-model scatter in the 2 m temperature over land, in the surface radiation fluxes, and in the cloud cover which implies a reduced confidence level for these variables. An erratum to this article can be found at  相似文献   

Performance of a multi-RCM ensemble for South Eastern South America   总被引：1，自引：1，他引：0  

A. F. Carril  C. G. Menéndez  A. R. C. Remedio  F. Robledo  A. S?rensson  B. Tencer  J.-P. Boulanger  M. de Castro  D. Jacob  H. Le Treut  L. Z. X. Li  O. Penalba  S. Pfeifer  M. Rusticucci  P. Salio  P. Samuelsson  E. Sanchez  P. Zaninelli 《Climate Dynamics》2012,39(12):2747-2768

The ability of four regional climate models to reproduce the present-day South American climate is examined with emphasis on La Plata Basin. Models were integrated for the period 1991–2000 with initial and lateral boundary conditions from ERA-40 Reanalysis. The ensemble sea level pressure, maximum and minimum temperatures and precipitation are evaluated in terms of seasonal means and extreme indices based on a percentile approach. Dispersion among the individual models and uncertainties when comparing the ensemble mean with different climatologies are also discussed. The ensemble mean is warmer than the observations in South Eastern South America (SESA), especially for minimum winter temperatures with errors increasing in magnitude towards the tails of the distributions. The ensemble mean reproduces the broad spatial pattern of precipitation, but overestimates the convective precipitation in the tropics and the orographic precipitation along the Andes and over the Brazilian Highlands, and underestimates the precipitation near the monsoon core region. The models overestimate the number of wet days and underestimate the daily intensity of rainfall for both seasons suggesting a premature triggering of convection. The skill of models to simulate the intensity of convective precipitation in summer in SESA and the variability associated with heavy precipitation events (the upper quartile daily precipitation) is far from satisfactory. Owing to the sparseness of the observing network, ensemble and observations uncertainties in seasonal means are comparable for some regions and seasons.  相似文献   

Sensitivity of climate models to seasonal variability of snow-free land surface albedo     

D. Rechid  S. Hagemann  D. Jacob 《Theoretical and Applied Climatology》2009,95(1-2):197-221

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Role of electrochemical reactions in pressure solution     

George W. Greene  Emily E. Meyer  Jacob N. Israelachvili 《Geochimica et cosmochimica acta》2009,73(10):2862-6892

Using a Surface Forces Apparatus we have measured changes in the electrical potential difference between quartz and mica surfaces that correlate with the changing quartz dissolution rate when surfaces are pressed together at relatively low pressures (2-3 atm) in aqueous electrolyte solutions of 30 mM CaCl₂ at 25 °C. No detectable dissolution or voltage potential difference is measured in symmetrical systems (e.g. mica-mica or quartz-quartz) or between dry surfaces subjected to similar pressures, indicating that the dissolution can not be attributed to a simple pressure effect, slow aging (creep), or plastic deformation of the quartz surface. In quartz-mica systems brought together under pressure or to close proximity in electrolyte solution, the onset of quartz dissolution is marked by a sudden, rapid decrease in the quartz thickness at initial rates in the range from 1 to 4 nm/min, which after several hours settles into a constant rate of approximately 0.01 nm/min (∼5 μm/yr). Concomitantly, the potential drops to a constant value once the dissolution rate has stabilized. The decrease in the decay rate is interpreted as being due to saturation of the confined aqueous film and/or to the buildup of a Stern layer on the quartz surface, and the constant rate as being due to the steady-state chemical dissolution and diffusion of the dissolving silica into the surrounding reservoir. The dissolution is ‘non-uniform’: the surfaces become rough as dissolution proceeds, with the appearance of pits in a manner analogous to corrosion. On occasions, the process of rapid dissolution followed by a gradual transition to steady dissolution repeats itself, suggesting that the pit structure and Stern layer are fragile and subject to collapse and/or expulsion from the gap. Preliminary experiments on the dissolution of multi-faceted milled quartz particles (∼1.0 μm diameter) compressed between two muscovite surfaces suggest an asymmetry in the dissolution rates at different crystallographic planes. The origin of the electrical potential is interpreted as arising from the overlapping of the electric double-layers of two dissimilar surfaces when they are forced into close proximity. This electrical potential difference, for as yet unknown reasons, appears to be the driving force for the dissolution, rather than pressure.  相似文献