Blind Construction of Optimal Nonlinear Recursive Predictors for Discrete Sequences

We present a new method for nonlinear prediction of discrete random sequences under minimal structural assumptions. We give a mathematical construction for optimal predictors of such processes, in the form of hidden Markov models. We then describe an algorithm, CSSR (Causal-State Splitting Reconstruction), which approximates the ideal predictor from data. We discuss the reliability of CSSR, its data requirements, and its performance in simulations. Finally, we compare our approach to existing methods using variable-length Markov models and cross-validated hidden Markov models, and show theoretically and experimentally that our method delivers results superior to the former and at least comparable to the latter.Comment: 8 pages, 4 figure

An Algorithm for Pattern Discovery in Time Series

We present a new algorithm for discovering patterns in time series and other sequential data. We exhibit a reliable procedure for building the minimal set of hidden, Markovian states that is statistically capable of producing the behavior exhibited in the data -- the underlying process's causal states. Unlike conventional methods for fitting hidden Markov models (HMMs) to data, our algorithm makes no assumptions about the process's causal architecture (the number of hidden states and their transition structure), but rather infers it from the data. It starts with assumptions of minimal structure and introduces complexity only when the data demand it. Moreover, the causal states it infers have important predictive optimality properties that conventional HMM states lack. We introduce the algorithm, review the theory behind it, prove its asymptotic reliability, use large deviation theory to estimate its rate of convergence, and compare it to other algorithms which also construct HMMs from data. We also illustrate its behavior on an example process, and report selected numerical results from an implementation.Comment: 26 pages, 5 figures; 5 tables; http://www.santafe.edu/projects/CompMech Added discussion of algorithm parameters; improved treatment of convergence and time complexity; added comparison to older method

Energy and emissions : local and global effects of the rise of China and India

Part 1 of the paper reviews recent trends in fossil fuel use and associated externalities. It also argues that the recent run-up in international oil prices reflects growing concerns about supply constraints associated with declining spare capacity in OPEC, refining bottlenecks, and geopolitical uncertainties rather than growing incremental use of oil by China and India. Part 2 compares two business as usual scenarios with a set of alternate scenarios based on policy interventions on the demand for or supply of energy and different assumptions about rigidities in domestic and international energy markets. The results suggest that energy externalities are likely to worsen significantly if there is no shift in China's and India's energy strategies. High energy demand from China and India could constrain some developing countries'growth through higher prices on international energy markets, but for others the"growth retarding"effects of higher energy prices are partially or fully offset by the"growth stimulating"effects of the larger markets in China and India. Given that there are many inefficiencies in the energy system in both China and India, there is an opportunity to reduce energy growth without adversely affecting GDPgrowth. The cost of a decarbonizing energy strategy will be higher for China and India than a fossil fuel-based strategy, but the net present value of delaying the shift will be higher than acting now. The less fossil fuel dependent alternative strategies provide additional dividends in terms of energy security.Energy Production and Transportation,Environment and Energy Efficiency,Energy and Environment,Energy Demand,Transport Economics Policy&Planning

Addressing China's growing water shortages and associated social and environmental consequences

China has experienced a wide-scale and rapid transformation from an agricultural based economy to the manufacturing workshop of the world. The associated relocation of the population from relatively low density rural areas to very high density urban areas is having a significant impact on the quantity and quality of water available as inputs into the production and consumption process, as well as the ability of the water system to absorb and neutralize the waste byproducts deposited into it. Water shortages are most severe in the north of the country, where surface water diversion is excessive and groundwater is being depleted. In addition, the quality of water is deteriorating because of pollution, thereby aggravating existing water shortages. The biggest challenge ahead will be for national and local governments to craft policies and rules within China's complex cultural and legal administrative system that provide incentives for users to increase efficiency of water use, and for polluters to clean up the water they use and return clean water to stream flows. Using a standard public economics framework, water requirements for public goods-such as ecosystem needs-should be set aside first, before allocating property rights in water (to enable water markets to functionand generate efficient allocation signals). Even then, water markets will have to be regulated to ensure public goods, such as public health, are not compromised. Until water markets are implemented, staying the course on increasing water and wastewater prices administratively and encouraging water conservation are necessary to reduce the wasting of current scarce water resources, as well as the new water supplies to be provided in the future.Water Supply and Sanitation Governance and Institutions,Town Water Supply and Sanitation,Water and Industry,Water Conservation,Water Use

Climate change and the economics of targeted mitigation in sectors with long-lived capital stock

Mitigation investments in long-lived capital stock (LLKS) differ from other types of mitigation investments in that, once established, LLKS can lock-in a stream of emissions for extended periods of time. Moreover, historical examples from industrial countries suggest that investments in LLKS projects or networks tend to be lumpy, and tend to generate significant indirect and induced emissions besides direct emissions. Looking forward, urbanization and rapid economic growth suggest that similar decisions about LLKS are being or will soon be made in many developing countries. In their current form, carbon markets do not provide correct incentives for mitigation investments in LLKS because the constraint on carbon extends only to 2012, and does not extend to many developing countries. Targeted mitigation programs in regions and sectors in which LLKS is being built at rapid rate are thus necessary to avoid getting locked into highly carbon-intensive LLKS. Even if the carbon markets were extended (geographically, sectorally, and over time), public intervention would still be required, for three main reasons. First, to ensure that indirect and induced emissions associated with LLKS are taken into account in investor’s financial cost-benefit analysis. Second, to facilitate project or network financing to bridge the gap between carbon revenues that accrue over time as the project/network unfolds and the capital needed upfront to finance lumpy investments. Third, to internalize other non-carbon externalities (e.g., local pollution) and/or to lift barriers (e.g., lack of capacity to handle new technologies) that penalize the low-carbon alternatives relative to the high-carbon ones.Transport Economics Policy&Planning,Climate Change Mitigation and Green House Gases,Climate Change Economics,Energy Production and Transportation,Energy and Environment

Will the Kyoto Protocol affect growth in Russia?

In light of the recent argument that rapid economic growth in Russia over the next decade, might result in emissions higher than the Kyoto target, thereby putting much-needed growth at risk, the authors revisit the discussion on the costs and benefits of ratification of the Kyoto Protocol by Russia. They conclude that even under a very high economic growth assumption, and even under very conservative assumptions about the decoupling between carbon dioxide emissions, and economic growth, Russia still benefits from a net surplus of emissions allowances, and thus will not see its growth adversely affected by the Kyoto target. In addition, a review of the possible costs, and benefits of the Kyoto Protocol suggests that the potential sale of excess allowances, far outweighs the other costs.Environmental Economics&Policies,Economic Theory&Research,Global Environment Facility,Climate Change,Montreal Protocol,Climate Change,Energy and Environment,Environmental Economics&Policies,Montreal Protocol,Carbon Policy and Trading