Showing papers by "Eric Chu published in 2016"

Conic Optimization via Operator Splitting and Homogeneous Self-Dual Embedding

Abstract: We introduce a first-order method for solving very large convex cone programs. The method uses an operator splitting method, the alternating directions method of multipliers, to solve the homogeneous self-dual embedding, an equivalent feasibility problem involving finding a nonzero point in the intersection of a subspace and a cone. This approach has several favorable properties. Compared to interior-point methods, first-order methods scale to very large problems, at the cost of requiring more time to reach very high accuracy. Compared to other first-order methods for cone programs, our approach finds both primal and dual solutions when available or a certificate of infeasibility or unboundedness otherwise, is parameter free, and the per-iteration cost of the method is the same as applying a splitting method to the primal or dual alone. We discuss efficient implementation of the method in detail, including direct and indirect methods for computing projection onto the subspace, scaling the original problem data, and stopping criteria. We describe an open-source implementation, which handles the usual (symmetric) nonnegative, second-order, and semidefinite cones as well as the (non-self-dual) exponential and power cones and their duals. We report numerical results that show speedups over interior-point cone solvers for large problems, and scaling to very large general cone programs.

Roadmap towards justice in urban climate adaptation research

Abstract: The 2015 United Nations Climate Change Conference in Paris (COP21) highlighted the importance of cities to climate action, as well as the unjust burdens borne by the world's most disadvantaged peoples in addressing climate impacts. Few studies have documented the barriers to redressing the drivers of social vulnerability as part of urban local climate change adaptation efforts, or evaluated how emerging adaptation plans impact marginalized groups. Here, we present a roadmap to reorient research on the social dimensions of urban climate adaptation around four issues of equity and justice: (1) broadening participation in adaptation planning; (2) expanding adaptation to rapidly growing cities and those with low financial or institutional capacity; (3) adopting a multilevel and multi-scalar approach to adaptation planning; and (4) integrating justice into infrastructure and urban design processes. Responding to these empirical and theoretical research needs is the first step towards identifying pathways to more transformative adaptation policies.

Equity Impacts of Urban Land Use Planning for Climate Adaptation: Critical Perspectives from the Global North and South

Abstract: A growing number of cities are preparing for climate change impacts by developing adaptation plans. However, little is known about how these plans and their implementation affect the vulnerability of the urban poor. We critically assess initiatives in eight cities worldwide and find that land use planning for climate adaptation can exacerbate socio-spatial inequalities across diverse developmental and environmental conditions. We argue that urban adaptation injustices fall into two categories: acts of commission, when interventions negatively affect or displace poor communities, and acts of omission, when they protect and prioritize elite groups at the expense of the urban poor.

The Governance of Climate Change Adaptation Through Urban Policy Experiments

Abstract: Climate change is increasingly posing risks to infrastructure and public services in cities across the global South. Building on ideas of policy experimentation at the nexus of institutional and transition theories, this paper assesses six climate change adaptation experiments across the cities of Surat, Indore and Bhubaneswar in India to uncover the politics behind how experiments are conceived of, implemented, and supported in light of local development needs. Through employing both embedded and cross-case comparative methods, I argue that policy experiments are often framed around achieving tangible urban economic benefits and maximizing specific project complementarities, which allow emerging adaptation priorities access to established policy directives and funding streams. However, I conclude that despite being arenas for testing new ideas, quantifying climate and development co-benefits, and engaging private and civil society actors, adaptation policy experiments must be coherent with urban political economic contexts in order for them to affect sustained, equitable and transformative programmatic change.

The political economy of urban climate adaptation and development planning in Surat, India:

Abstract: This paper argues for a political economic approach to understanding climate change adaptation and development planning in an urban context. Based on field research conducted in Surat, India, across a period of two years, I illustrate how climate adaptation is rooted in preexisting and contextually specific urban political relationships that can be traced through the city's developmental history. Through assessing Surat's experience with recent industrialization, episodes of natural disasters, to more recent engagement with the Asian Cities Climate Change Resilience Network, I highlight how adaptation planning, as well as how adaptation is integrated into urban development planning, occurs through processes of prioritizing adaptation against development needs and implementing options that are cocreated among public and civic actors. This case empirically shows how adaptation is mainstreamed into urban development planning, illustrates the trade-offs associated with how different urban actors plan and implement adaptation in the context of rapid industrialization, and assesses how internationally funded adaptation programs are operationalized in the context of local social and political realities.

An Ecosystem Approach to Disaster Risk Reduction: The Challenges of Multilevel Governance

Abstract: In response to the increasing frequency of extreme disaster events across the world, scholars of disaster risk reduction (DRR) are showing interest in the opportunities presented by ecosystem-based approaches (Renaud et al., 2013; Uy and Shaw, 2012; Sudmeier-Rieux et al., 2006; Sudmeier-Rieux et al., 2009). Recent research has highlighted the effectiveness of ecosystem functions and services for reducing disaster risks, including coastal and urban flooding, tsunami, and storm surges (Kathiresan and Rajendran, 2005; Spalding, 2014; Nel et al., 2014). However, in addition to the importance of physical ecosystem functions for providing risk reduction benefits, we must also understand how an ecosystem-based approach can be better implemented and governed across different spaces and scales to yield more effective disaster risk reduction policies and actions.

Corrigendum:: Roadmap towards justice in urban climate adaptation research

Abstract: Nature Climate Change 6, 131–137 (2016); published online 27 January 2016; corrected after print 26 April 2016 In the version of this Perspective originally published, it was not acknowledged that this work was contributing to the ICTA 'Unit of Excellence'. This correction has been made to the online version.

Backward Errors and Small Sample Condition Estimation for $\star$-Sylveter Equations

Abstract: In this paper, we adopt a componentwise perturbation analysis for $\star$-Sylvester equations. Based on the small condition estimation (SCE), we devise the algorithms to estimate normwise, mixed and componentwise condition numbers for $\star$-Sylvester equations. We also define a componentwise backward error with a sharp and easily computable bound. Numerical examples illustrate that our algorithm under componentwise perturbations produces reliable estimates, and the new derived computable bound for the componentwise backward error is sharp and reliable for well conditioned and moderate ill-conditioned $\star$-Sylvester equations under large or small perturbations.