Modeling endogenous technological change for climate policy analysis

The approach used to model technological change in a climate policy model is a critical determinant of its results in terms of the time path of CO2 prices and costs required to achieve various emission reduction goals. We provide an overview of the different approaches used in the literature, with an emphasis on recent developments regarding endogenous technological change, research and development, and learning. Detailed examination sheds light on the salient features of each approach, including strengths, limitations, and policy implications. Key issues include proper accounting for the opportunity costs of climate-related knowledge generation, treatment of knowledge spillovers and appropriability, and the empirical basis for parameterizing technological relationships. No single approach appears to dominate on all these dimensions, and different approaches may be preferred depending on the purpose of the analysis, be it positive or normative. �� 2008 Elsevier B.V. All rights reserved.

A Hard Bargain? A cost-benefit analysis of an improved cookstove program in India

In developing countries, access to modern energy for cooking and heating still remains a challenge to raising households out of poverty. About 2.5 billion people depend on solid fuels such as biomass, wood, charcoal and animal dung. The use of solid fuels has negative outcomes for health, the environment and economic development (Universal Energy Access, UNDP). In low income countries, 1.3 million deaths occur due to indoor smoke or air pollution from burning solid fuels in small, confined and unventilated kitchens or homes. In addition, pollutants such as black carbon, methane and ozone, emitted when burning inefficient fuels, are responsible for a fraction of the climate change and air pollution. There are international efforts to promote the use of clean cookstoves in developing countries but limited evidence on the economic benefits of such distribution programs. This study undertook a systematic economic evaluation of a program that distributed subsidized improved cookstoves to rural households in India. The evaluation examined the effect of different levels of subsidies on the net benefits to the household and to society. This paper answers the question, ���Ex post, what are the economic benefits to various stakeholders of a program that distributed subsidized improved cookstoves?��� In addressing this question, the evaluation used empirical data from India applied to a cost-benefit model to examine how subsidies affect the costs and the benefits of the biomass improved cookstove and the electric improved cookstove to different stakeholders.

Contribution of the North Atlantic subtropical high to regional climate model (RCM) skill in simulating southeastern United States summer precipitation

�� 2014, Springer-Verlag Berlin Heidelberg.This study assesses the skill of advanced regional climate models (RCMs) in simulating southeastern United States (SE US) summer precipitation and explores the physical mechanisms responsible for the simulation skill at a process level. Analysis of the RCM output for the North American Regional Climate Change Assessment Program indicates that the RCM simulations of summer precipitation show the largest biases and a remarkable spread over the SE US compared to other regions in the contiguous US. The causes of such a spread are investigated by performing simulations using the Weather Research and Forecasting (WRF) model, a next-generation RCM developed by the US National Center for Atmospheric Research. The results show that the simulated biases in SE US summer precipitation are due mainly to the misrepresentation of the modeled North Atlantic subtropical high (NASH) western ridge. In the WRF simulations, the NASH western ridge shifts 7�� northwestward when compared to that in the reanalysis ensemble, leading to a dry bias in the simulated summer precipitation according to the relationship between the NASH western ridge and summer precipitation over the southeast. Experiments utilizing the four dimensional data assimilation technique further suggest that the improved representation of the circulation patterns (i.e., wind fields) associated with the NASH western ridge substantially reduces the bias in the simulated SE US summer precipitation. Our analysis of circulation dynamics indicates that the NASH western ridge in the WRF simulations is significantly influenced by the simulated planetary boundary layer (PBL) processes over the Gulf of Mexico. Specifically, a decrease (increase) in the simulated PBL height tends to stabilize (destabilize) the lower troposphere over the Gulf of Mexico, and thus inhibits (favors) the onset and/or development of convection. Such changes in tropical convection induce a tropical���extratropical teleconnection pattern, which modulates the circulation along the NASH western ridge in the WRF simulations and contributes to the modeled precipitation biases over the SE US. In conclusion, our study demonstrates that the NASH western ridge is an important factor responsible for the RCM skill in simulating SE US summer precipitation. Furthermore, the improvements in the PBL parameterizations for the Gulf of Mexico might help advance RCM skill in representing the NASH western ridge circulation and summer precipitation over the SE US.

Utility of a molecular prescreening program in advanced colorectal cancer for enrollment on biomarker-selected clinical trials.

BACKGROUND: Incorporation of multiple enrichment biomarkers into prospective clinical trials is an active area of investigation, but the factors that determine clinical trial enrollment following a molecular prescreening program have not been assessed. PATIENTS AND METHODS: Patients with 5-fluorouracil-refractory metastatic colorectal cancer at the MD Anderson Cancer Center were offered screening in the Assessment of Targeted Therapies Against Colorectal Cancer (ATTACC) program to identify eligibility for companion phase I or II clinical trials with a therapy targeted to an aberration detected in the patient, based on testing by immunohistochemistry, targeted gene sequencing panels, and CpG island methylation phenotype assays. RESULTS: Between August 2010 and December 2013, 484 patients were enrolled, 458 (95%) had a biomarker result, and 157 (32%) were enrolled on a clinical trial (92 on biomarker-selected and 65 on nonbiomarker selected). Of the 458 patients with a biomarker result, enrollment on biomarker-selected clinical trials was ninefold higher for predefined ATTACC-companion clinical trials as opposed to nonpredefined biomarker-selected clinical trials, 17.9% versus 2%, P < 0.001. Factors that correlated positively with trial enrollment in multivariate analysis were higher performance status, older age, lack of standard of care therapy, established patient at MD Anderson, and the presence of an eligible biomarker for an ATTACC-companion study. Early molecular screening did result in a higher rate of patients with remaining standard of care therapy enrolling on ATTACC-companion clinical trials, 45.1%, in contrast to nonpredefined clinical trials, 22.7%; odds ratio 3.1, P = 0.002. CONCLUSIONS: Though early molecular prescreening for predefined clinical trials resulted in an increase rate of trial enrollment of nonrefractory patients, the majority of patients enrolled on clinical trials were refractory to standard of care therapy. Within molecular prescreening programs, tailoring screening for preidentified and open clinical trials, temporally linking screening to treatment and optimizing both patient and physician engagement are efforts likely to improve enrollment on biomarker-selected clinical trials. CLINICAL TRIALS NUMBER: The study NCT number is NCT01196130.

Bridging the Scale Gap from Leaf to Canopy in Biosphere-Atmosphere Gas and Particle Exchanges

<p>Terrestrial ecosystems, occupying more than 25% of the Earth's surface, can serve as</p><p>`biological valves' in regulating the anthropogenic emissions of atmospheric aerosol</p><p>particles and greenhouse gases (GHGs) as responses to their surrounding environments.</p><p>While the signicance of quantifying the exchange rates of GHGs and atmospheric</p><p>aerosol particles between the terrestrial biosphere and the atmosphere is</p><p>hardly questioned in many scientic elds, the progress in improving model predictability,</p><p>data interpretation or the combination of the two remains impeded by</p><p>the lack of precise framework elucidating their dynamic transport processes over a</p><p>wide range of spatiotemporal scales. The diculty in developing prognostic modeling</p><p>tools to quantify the source or sink strength of these atmospheric substances</p><p>can be further magnied by the fact that the climate system is also sensitive to the</p><p>feedback from terrestrial ecosystems forming the so-called `feedback cycle'. Hence,</p><p>the emergent need is to reduce uncertainties when assessing this complex and dynamic</p><p>feedback cycle that is necessary to support the decisions of mitigation and</p><p>adaptation policies associated with human activities (e.g., anthropogenic emission</p><p>controls and land use managements) under current and future climate regimes.</p><p>With the goal to improve the predictions for the biosphere-atmosphere exchange</p><p>of biologically active gases and atmospheric aerosol particles, the main focus of this</p><p>dissertation is on revising and up-scaling the biotic and abiotic transport processes</p><p>from leaf to canopy scales. The validity of previous modeling studies in determining</p><p>iv</p><p>the exchange rate of gases and particles is evaluated with detailed descriptions of their</p><p>limitations. Mechanistic-based modeling approaches along with empirical studies</p><p>across dierent scales are employed to rene the mathematical descriptions of surface</p><p>conductance responsible for gas and particle exchanges as commonly adopted by all</p><p>operational models. Specically, how variation in horizontal leaf area density within</p><p>the vegetated medium, leaf size and leaf microroughness impact the aerodynamic attributes</p><p>and thereby the ultrane particle collection eciency at the leaf/branch scale</p><p>is explored using wind tunnel experiments with interpretations by a porous media</p><p>model and a scaling analysis. A multi-layered and size-resolved second-order closure</p><p>model combined with particle </p><p>uxes and concentration measurements within and</p><p>above a forest is used to explore the particle transport processes within the canopy</p><p>sub-layer and the partitioning of particle deposition onto canopy medium and forest</p><p>oor. For gases, a modeling framework accounting for the leaf-level boundary layer</p><p>eects on the stomatal pathway for gas exchange is proposed and combined with sap</p><p>ux measurements in a wind tunnel to assess how leaf-level transpiration varies with</p><p>increasing wind speed. How exogenous environmental conditions and endogenous</p><p>soil-root-stem-leaf hydraulic and eco-physiological properties impact the above- and</p><p>below-ground water dynamics in the soil-plant system and shape plant responses</p><p>to droughts is assessed by a porous media model that accommodates the transient</p><p>water </p><p>ow within the plant vascular system and is coupled with the aforementioned</p><p>leaf-level gas exchange model and soil-root interaction model. It should be noted</p><p>that tackling all aspects of potential issues causing uncertainties in forecasting the</p><p>feedback cycle between terrestrial ecosystem and the climate is unrealistic in a single</p><p>dissertation but further research questions and opportunities based on the foundation</p><p>derived from this dissertation are also brie</p><p>y discussed.</p>