Data-Driven Chance Constrained Optimization under Wasserstein Ambiguity Sets

We present a data-driven approach for distributionally robust chance constrained optimization problems (DRCCPs). We consider the case where the decision maker has access to a finite number of samples or realizations of the uncertainty. The chance constraint is then required to hold for all distributions that are close to the empirical distribution constructed from the samples (where the distance between two distributions is defined via the Wasserstein metric). We first reformulate DRCCPs under data-driven Wasserstein ambiguity sets and a general class of constraint functions. When the feasibility set of the chance constraint program is replaced by its convex inner approximation, we present a convex reformulation of the program and show its tractability when the constraint function is affine in both the decision variable and the uncertainty. For constraint functions concave in the uncertainty, we show that a cutting-surface algorithm converges to an approximate solution of the convex inner approximation of DRCCPs. Finally, for constraint functions convex in the uncertainty, we compare the feasibility set with other sample-based approaches for chance constrained programs.Comment: A shorter version is submitted to the American Control Conference, 201

The growth of transport cector CO2 emissions and underlying factors in Latin America and the Caribbean

This study examines the factors responsible for the growth of transport sector carbon dioxide emissions in 20 Latin American and Caribbean countries during 1980-2005 by decomposing the emissions growth into components associated with changes in fuel mix, modal shift, and economic growth, as well as changes in emission coefficients and transportation energy intensity. The key finding of the study is that economic growth and the changes in transportation energy intensity are the main factors driving transport sector carbon dioxide emissions growth in the countries considered. The results imply that fiscal policy instruments - such as subsidies to clean fuels and clean vehicles - would be more effective in reducing emissions in countries where the economic activity effect is the primary driver for transport sector carbon dioxide emissions growth. By contrast, regulatory policy instruments - such as vehicle efficiency standards and vehicle occupancy standards - would be more effective in countries where the transportation energy intensity effect is the main driver of carbon dioxide emissions growth. Both fiscal and regulatory policy instruments would be useful in countries where both economic activity and transportation energy intensity effects are responsible for driving transport sector carbon dioxide emissions growth.Transport Economics Policy&Planning,Energy Production and Transportation,Oil Refining&Gas Industry,Environment and Energy Efficiency,Energy and Environment

Biofuels : markets, targets and impacts

This paper reviews recent developments in biofuel markets and their economic, social and environmental impacts. Several countries have introduced mandates and targets for biofuel expansion. Production, international trade and investment have increased sharply in the past few years. However, several existing studies have blamed biofuels as one of the key factors behind the 2007-2008 global food crisis, although the magnitudes of impacts in these studies vary widely depending on the underlying assumptions and structure of the models. Existing studies also have huge disparitiesin the magnitude of long-term impacts of biofuels on food prices and supply; studies that model only the agricultural sector show higher impacts, whereas studies that model the entire economy show relatively lower impacts. In terms of climate change mitigation impacts, there exists a consensus that current biofuels lead to greenhouse gas mitigation only when greenhouse gas emissions related to land-use change are not counted. If conversion of carbon rich forest land to crop land is not avoided, the resulting greenhouse gas release would mean that biofuels would not reduce cumulative greenhouse gas emissions until several years had passed. Overall, results from most of the existing literature do not favor diversion of food for large-scale production of biofuels, although regulated production of biofuels in countries with surplus land and a strong biofuel industry are not ruled out. Developments in second generation biofuels offer some hope, yet they still compete with food supply through land use and are currently constrained by a number of technical and economic barriers.Energy Production and Transportation,Renewable Energy,Climate Change Mitigation and Green House Gases,Food&Beverage Industry,Environmental Economics&Policies

Why have CO2 emissions increased in the transport sector in Asia ? underlying factors and policy options

Rapidly increasing emissions of carbon dioxide from the transport sector, particularly in urban areas, is a major challenge to sustainable development in developing countries. This study analyzes the factors responsible for transport sector CO2 emissions growth in selected developing Asian countries during 1980-2005. The analysis splits the annual emissions growth into components representing economic development; population growth; shifts in transportation modes; and changes in fuel mix, emission coefficients, and transportation energy intensity. The study also reviews existing government policies to limit CO2 emissions growth, particularly various fiscal and regulatory policy instruments. The study finds that of the six factors considered, three - economic development, population growth, and transportation energy intensity - are responsible for driving up transport sector CO2 emissions in Bangladesh, the Philippines, and Vietnam. In contrast, only economic development and population growth are responsible in the case of China, India, Indonesia, Republic of Korea, Malaysia, Pakistan, Sri Lanka, and Thailand. CO2 emissions exhibit a downward trend in Mongolia due to decreasing transportation energy intensity. The study also finds that some existing policy instruments help reduce transport sector CO2 emissions, although they were not necessarily targeted for this purpose when introduced.Transport Economics Policy&Planning,Climate Change Mitigation and Green House Gases,Energy Production and Transportation,Climate Change Economics,Transport and Environment