JP

Formation of Ozone and Growth of Aerosols in Young Smoke Plumes From Biomass Burning, Part 1: Lagrangian Parcel Studies

We have developed a new model of the gas? and aerosol?phase chemistry of biomass burning smoke plumes called Aerosol Simulation Program (ASP). Here we use ASP combined with a Lagrangian parcel model to simulate the chemistry in smoke plumes from three fires: the Otavi savannah fire in Namibia, an Alaska boreal forest fire, and the Timbavati savannah fire. Our model explained the observations of ozone in the Otavi and Alaska plumes fairly well, but our initial model simulation of the Timbavati plume underestimated the concentrations of ozone, OH, and secondary aerosol matter. The Timbavati simulation agrees with observations if we increase OH to equal its observed levels. Heterogeneous reactions of NO2 and SO2 could explain the needed higher concentrations of OH and the rapid formation of ozone, nitrate, and sulfate in the smoke plume if the uptake coefficients on smoke aerosols are large (O(10−3) and O(10−4), respectively). Uncharacterized organic species in the smoke plume were likely responsible for the rapid formation of aerosol organic carbon. The changes in the aerosol size distribution were dominated by plume dilution and condensational growth. The single scattering albedo of the modeled smoke increases from 0.866 to 0.902 over 1 h of aging. The change in aerosol scattering with relative humidity for the modeled fresh smoke matches observations up to 66% RH, but the model greatly overestimates the humidification factor at 80% RH (2.88 versus an observed value of 1.70–1.79). For the aged smoke, the modeled humidification factor is 1.22, slightly below the observed value of 1.40.

Formation of Ozone and Growth of Aerosols in Young Smoke Plumes From Biomass Burning, Part 2: 3D Eulerian Studies

Global?scale models of atmospheric chemistry (GACMs) “mix” biomass burning emissions into grid boxes with horizontal scales of 10–200 km. This ignores the complex nonlinear transformations that take place in the young smoke plumes. Here we use a new gas? and aerosol?phase chemistry model called Aerosol Simulation Program (ASP) and a 3?D Eulerian smoke plume model to simulate the fluid dynamics, radiative transfer, gas?phase chemistry, and aerosol?phase chemistry of the Timbavati smoke plume observed during SAFARI 2000. We then compare the results of the 3?D plume model with those of an Eulerian box model, which is used as an analog for the large grid boxes of GACMs. The 3?D plume model matched the observed plume injection height but required a large minimum horizontal diffusion coefficient to match the observed horizontal dispersion of the plume. Absorption and scattering by smoke aerosols reduced the modeled photolysis rates in the plume by 10–20%. Increasing the heterogeneous production of HONO and H2SO4 in the model and including uncharacterized organic species using monoterpenes as a proxy compound improves the model?observation match. Direct measurements of OH in the smoke plumes would be an excellent way to determine if heterogeneous production of HONO is taking place. The automatic dilution of smoke plume emissions into the large grid boxes of global models can result in large errors in predicted concentrations of O3, NOx and aerosol species downwind. We discuss several potential approaches that could reduce these errors.

Forward-Looking Versus Recursive-Dynamic Modeling in Climate Policy Analysis: A Comparison

This paper develops a multi-regional general equilibrium model for climate policy analysis based on the latest version of the MIT Emissions Prediction and Policy Analysis (EPPA) model. We develop two versions so that we can solve the model either as a fully inter-temporal optimization problem (forward-looking, perfect foresight) or recursively. The standard EPPA model on which these models are based is solved recursively, and it is necessary to simplify some aspects of it to make inter-temporal solution possible. The forward-looking capability allows one to better address economic and policy issues such as borrowing and banking of GHG allowances, efficiency implications of environmental tax recycling, endogenous depletion of fossil resources, international capital flows, and optimal emissions abatement paths among others. To evaluate the solution approaches, we benchmark each version to the same macroeconomic path, and then compare the behavior of the two versions under a climate policy that restricts greenhouse gas emissions. We find that the energy sector and CO2 price behavior are similar in both versions (in the recursive version of the model we force the inter-temporal theoretical efficiency result that abatement through time should be allocated such that the CO2 price rises at the interest rate.) The main difference that arises is that the macroeconomic costs are substantially lower in the forward-looking version of the model, since it allows consumption shifting as an additional avenue of adjustment to the policy. On the other hand, the simplifications required for solving the model as an optimization problem, such as dropping the full vintaging of the capital stock and fewer explicit technological options, likely have effects on the results. Moreover, inter-temporal optimization with perfect foresight poorly represents the real economy where agents face high levels of uncertainty that likely lead to higher costs than if they knew the future with certainty. We conclude that while the forward-looking model has value for some problems, the recursive model produces similar behavior in the energy sector and provides greater flexibility in the details of the system that can be represented.
© Elsevier, 2009

From Science to Policy: The Science-Related Politics of Climate Change Policy in the U.S.

Global climate change is on the political agenda primarily as a result of science and the warnings of the scientific community, and is commonly seen as a quintessentially scientific matter. However, the development of policy on this issue in the U.S. today does not turn on the scientific evidence. Rather, policy is determined by the political and economic forces involved, with reference to the science only to support positions reached on other grounds. The reasons relate primarily to the uncertainty in the evidence, the structure and politics of the government, the economic costs and impact of change and of policies to reduce greenhouse gases, the international structure in which the issue is being confronted, the role of the media, and the effects of partisan politics. In this situation, the scientific and engineering communities (including social scientists and especially economists) have a major responsibility to maintain their professional values and objectivity so dominated at the moment by other pressures. Only that way can they retain the public trust that will be necessary if and when costly policy measures must be undertaken.

Future Carbon Regulations and Current Investments in Alternative Coal-Fired Power Plant Designs

This paper assesses the role of uncertainty over future U.S. carbon regulations in shaping the current choice of which type of power plant to build. The pulverized coal technology (PC) still offer the lowest cost power—assuming there is no need to control emissions of carbon. The integrated coal gasification combined cycle technology (IGCC) may be cheaper if carbon must be captured. Since a plant built now will be operated for many years, and since carbon regulations may be instituted in the future, a U.S. electric utility must make the current investment decision in light of the uncertain future regulatory rules. This paper shows how this decision is to be made. We start by describing the economics of the two key coal-fired power plant technologies, PC and IGCC. We then analyze the potential costs of future carbon regulations, including the costs of retrofitting the plant with carbon capture technology and the potential cost of paying charges for emissions. We present the economics of each design in the form of a cash flow spreadsheet yielding the present value cost, and show the results for different scenarios of emissions regulation. We then discuss how to incorporate uncertainty about the future regulation of carbon emissions into the decision to build one plant design or the other. As an aid to decision making, we provide some useful benchmarks for possible future regulation and show how these benchmarks relate back to the relative costs of the two technologies and the optimal choice for the power plant investment. Few of the scenarios widely referenced in the public discussion warrant the choice of the IGCC technology. Instead, the PC technology remains the least costly. The level of future regulation required to justify a current investment in the IGCC technology appears to be very aggressive, if not out of the question. However, the current price placed on carbon emissions in the European Trading System, is higher than these benchmarks. If it is any guide to possible future penalties for emissions in the U.S., then current investment in the IGCC technology is warranted.

Future Carbon Regulations and Current Investments in Alternative Coal-Fired Power Plant Technologies

We analyze how uncertain future US carbon regulations shape the current choice of the type of power plant to build. Our focus is on two coal-fired technologies, pulverized coal (PC) and integrated coal gasification combined cycle technology (IGCC). The PC technology is cheapest — assuming there is no need to control carbon emissions. The IGCC technology may be cheaper if carbon must be captured. Since power plants last many years and future regulations are uncertain, a US electric utility faces a standard decision under uncertainty. A company will confront the range of possible outcomes, assigning its best estimate of the probability of each scenario, averaging the results and determining the power plant technology with the lowest possible cost inclusive of expected future carbon related costs, whether those costs be in the form of emissions charges paid or capital expenditures for retrofitting to capture carbon. If the company assigns high probability to no regulation or to less stringent regulation of carbon, then it makes sense for it to build the PC plant. But if it assigns sufficient probability to scenarios with more stringent regulation, then the IGCC technology is warranted. We provide some useful benchmarks for possible future regulation and show how these relate back to the relative costs of the two technologies and the optimal technology choice. Few of the policy proposals widely referenced in the public discussion warrant the choice of the IGCC technology. Instead, the PC technology remains the least costly. However, recent carbon prices in the European Emissions Trading System are higher than these benchmarks. If it is any guide to possible future penalties for emissions in the US, then current investment in the IGCC technology is warranted. Of course, other factors need to be factored into the decision as well.

© 2006 Elsevier

Future Effects of Ozone on Carbon Sequestration and Climate Change Policy Using a Global Biogeochemical Model

Exposure of plants to ozone inhibits photosynthesis and therefore reduces vegetation production and carbon sequestration. The reduced carbon storage would then require further reductions in fossil fuel emissions to meet a given CO2 concentration target, thereby increasing the cost of meeting the target. Simulations with the Terrestrial Ecosystem Model (TEM) for the historical period (1860-1995) show the largest damages occur in the Southeast and Midwestern regions of the United States, eastern Europe, and eastern China. The largest reductions in carbon storage for the period 1950-1995, 41%, occur in eastern Europe. Scenarios for the 21st century developed with the MIT Integrated Global Systems Model (IGSM) lead to even greater negative effects on carbon storage in the future. In some regions, current land carbon sinks become carbon sources, and this change leads to carbon sequestration decreases of up to 0.4 Pg C/yr due to damage in some regional ozone hot spots. With a climate policy, failing to consider the effects of ozone damage on carbon sequestration would raise the global costs over the next century of stabilizing atmospheric concentrations of CO2 equivalents at 550 ppm by 6 to 21%. Because stabilization at 550 ppm will reduce emission of other gases that cause ozone, these additional benefits are estimated to be between 5 and 25% of the cost of the climate policy. Tropospheric ozone effects on terrestrial ecosystems thus produce a surprisingly large feedback in estimating climate policy costs that, heretofore, has not been included in cost estimates. © 2005 Springer Science+Business Media

Future light-duty vehicles: Predicting their fuel consumption and carbon-reduction potential

The transportation sector in the United States is a major contributor to global energy consumption and carbon dioxide emission. To assess the future potentials of different technologies in addressing these two issues, we used a family of simulation programs to predict fuel consumption for passenger cars in 2002. The selected technology combinations that have good market potential and could be in mass production include: advanced gasoline and diesel internal combustion engine vehicles with automatically shifting clutched transmissions, gasoline, diesel, and compressed natural gas hybrid electric vehicles with continuously variable transmissions, direct hydrogen, gasoline and methanol reformer fuel cell hybrid electric vehicles with direct ratio drive, and battery electric vehicle with direct ratio drive. Using appropriately researched assumptions and input variables, calculations were performed to estimate the energy consumption and carbon dioxide emissions of the different technology combinations. Comparing the results for the vehicle driving cycle only, an evolutionary fuel consumption improvement of about 35 percent can be expected for the baseline gasoline car, given only market pressures and gradual regulatory requirements. With more research and investment in technology, an advanced gasoline engine car may further reduce fuel consumption by 12%, and a gasoline electric hybrid by 40%, as compared to the evolutionary car. Diesel versions of the advanced combustion and hybrid vehicles may be 10-15% better than their gasoline counterparts. Compressed natural gas hybrid vehicle may reduce fuel consumption by 3-4% but may reduce carbon dioxide emission by 25%. Meanwhile, a direct hydrogen fuel cell electric hybrid vehicle may have the greatest improvement over the baseline at 55%, but the gasoline and methanol reformers fuel cell versions appear very expensive and offer little benefit. Finally, aside from critical battery limitations, the electric vehicle is difficult to compare to other vehicles without taking into account the electricity generation process.

©2001 SAE International

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