Computable explicit bounds for the discretization error of variable stepsize multistep methods

This paper deals with the achievement of explicit computable bounds for the global discretization error of variable stepsize multistep methods which are perturbation of strongly stable fixed stepsize methods. The approach is based on the study of the growth of solutions of certain variable coefficient difference equations satisfied by the global discretization error.     

基于CGE模型的有色金属价格变动对区域经济发展影响的实证分析

有色金属作为国民经济基础性产业,其价格波动影响着经济发展的稳定性,尤其是以有色金属产业为经济支柱的西部地区。本文运用投入产出表及相关统计数据,通过构建有色金属CGE模型,根据近年铅、铜、锌、铝、镍等五种常用有色金属价格的波动范围,拟设置了六种波动情景进行模拟,即有色金属价格波动在-40%、-25%、-10%、10%、25%、40%情景下,实证模拟价格变动对云南经济的影响。结果显示,实际GDP、居民收入、政府收入随有色金属价格上涨而降低;企业收入、要素价格随有色金属价格上涨而提高;多数部门产出因有色金属价格上涨而减少;多数部门增加值因有色金属价格上涨而提高。有色金属价格下降则呈现出相反的结果。结果表明,有色金属价格对宏观经济的影响具有非对称性,价格上涨对经济的消极影响要显著大于价格下降对经济的积极作用,具有高附加值的精深加工行业发展乏力,尤其需要大力优化升级。     

Impact of climate model uncertainties on socioeconomics: A case study with a medium mitigation scenario

Carbon dioxide (CO₂) emissions are strongly associated with economy. The amount of CO₂ that human society can emit in order to achieve a climate target depends on physical and biogeochemical properties in the climate system; these vary among climate models or earth system models (ESMs). Thus, uncertainties in such models, the spread remained when we both consider the range of existing models and observational data for key variables, can affect analysis of future global economy. In this study, using a computable general equilibrium model, we analyze the impacts on socioeconomics under a medium climate mitigation scenario by following three emission pathways considering uncertainties in existing ESMs (the lower and upper bounds as well as the mean). The results indicate that the impacts are larger in the lower bound case, despite the fact that economic and energy demands will increase continuously. In a comparison between the upper and lower bound cases, the carbon price of the latter case is approximately three times higher than that of the former case in 2100. Consequently, primary/final energy demand in the lower bound case becomes 1.0%/14% lower, and more renewables and carbon capture and storage are required to be used. Furthermore, the gross domestic product in the lower bound case is 4.1% smaller. Thus, within the scenario, the socioeconomic impacts caused by ESM uncertainties are not insignificant, but are smaller than the differences in annual and cumulative emissions.     

The long-run impact of energy prices on world agricultural markets: The role of macro-economic linkages

The world prices of some food and energy products have followed similar large swings in recent years. We investigate the long-run relationship between these prices using a world Computable General Equilibrium model with detailed representations of food and energy markets. Particular attention is paid to specifying macro-economic linkages which have often been overlooked in recent analysis and debate. We find that the omission of these macro-economic linkages has a substantial bearing on this relationship. A positive relationship due to the cost push effect has been identified in most analysis, but we find that the introduction of the real income effect may indeed imply a negative relationship between world food and energy prices.     

Characterizing Programming Systems Allowing Program Self-Reference

The interest is in characterizing insightfully the power of program self-reference in effective programming systems ( ), the computability-theoretic analogs of programming languages (for the partial computable functions). In an in which the constructive form of Kleene’s Recursion Theorem (KRT) holds, it is possible to construct, algorithmically, from an arbitrary algorithmic task, a self-referential program that, in a sense, creates a self-copy and then performs that task on the self-copy. In an in which the not-necessarily-constructive form of Kleene’s Recursion Theorem (krt) holds, such self-referential programs exist, but cannot, in general, be found algorithmically. In an earlier effort, Royer proved that there is no collection of recursive denotational control structures whose implementability characterizes the in which KRT holds. One main result herein, proven by a finite injury priority argument, is that the in which krt holds are, similarly, not characterized by the implementability of some collection of recursive denotational control structures. On the positive side, however, a characterization of such of a rather different sort is shown herein. Though, perhaps not the insightful characterization sought after, this surprising result reveals that a hidden and inherent constructivity is always present in krt. This paper is an expanded version of [6]. This paper received support from NSF Grant CCR-0208616. “Know thyself.” Greek proverb     

Analysis of the economic impact of different Chinese climate policy options based on a CGE model incorporating endogenous technological change

Abatement cost is the main concern for climate change mitigation and the key factor for mitigation cost is technological change. This study established an integrated economic, energy, environmental, dynamic, computable general equilibrium (CGE) model representing endogenous technological change for China's climate change policy analysis. This study analyzed and compared the economic impact of different approaches to mitigation commitments as well as the potential role of technological change in the formulation of mitigation targets and commitments, taking into account China's climate policy-making needs based on the current international climate negotiation process. The results show that, absolute emission limits similar to the Kyoto Protocol will seriously impede the future economic development of China, while the impact of an 80% reduction in carbon intensity, forecast for 2050 based on the 2005 level, is relatively small. Technological change can promote economic growth, improve energy efficiency and reduce carbon intensity per unit of output through the substitution of production factors. Consequently it can reduce marginal abatement cost and related GDP loss by mitigation. At the same time it can increase mitigation potentials and extend the emission reduction amount, showing that consideration of the impact of technological change when deciding the emission reduction targets is necessary.     

Concurrent and legacy economic and environmental impacts from establishing a marine energy sector in Scotland

We examine the economic and environmental impact that the installation of 3 GW of marine energy capacity would have on Scotland. This is not a forecast, but a projection of the likely effects of meeting the Scottish Government's targets for renewable energy through the development of a marine energy sector. Energy, with a particular focus on renewables, is seen by the Scottish Government as a “key sector”, with high growth potential and the capacity to boost productivity (Scottish Government, 2007a. The Government Economic Strategy. The Scottish Government, Edinburgh). The key nature of this sector has been identified through targets being set for renewable energy to achieve environmental and economic benefits. Using a regional computable general equilibrium (CGE) model of Scotland we show that the development of a marine energy sector can have substantial and beneficial impacts on GDP, employment and the environment over the lifetime of the devices, given the encouragement of strong indigenous inter-industry linkages. Furthermore, there are also substantial “legacy” effects that persist well beyond the design life of the devices.     

The economic impact of restricted water supply: a computable general equilibrium analysis

Water problems are typically studied at the level of the river catchment. About 70% of all water is used for agriculture, and agricultural products are traded internationally. A full understanding of water use is impossible without understanding the international market for food and related products, such as textiles. The water embedded in commodities is called virtual water. Based on a general equilibrium model, we offer a method for investigating the role of water resources and water scarcity in the context of international trade. We run five alternative scenarios, analyzing the effects of water scarcity due to reduced availability of groundwater. This can be a consequence of physical constraints, and of policies curbing water demand. Four scenarios are based on a market solution, where water owners can capitalize their water rent or taxes are recycled. In the fifth non-market scenario, this is not the case; supply restrictions imply productivity losses. Restrictions in water supply would shift trade patterns of agriculture and virtual water. These shifts are larger if the restriction is larger, and if the use of water in production is more rigid. Welfare losses are substantially larger in the non-market situation. Water-constrained agricultural producers lose, but unconstrained agricultural produces gain; industry gains as well. As a result, there are regional winners and losers from water supply constraints. Because of the current distortions of agricultural markets, water supply constraints could improve allocative efficiency; this welfare gain may more than offset the welfare losses due to the resource constraint.