Nitrogen oxide (NO_x) is a prevalent air pollutant across the United States and a requisite precursor for tropospheric (ground-level) ozone formation. Both pollutants significantly impact human health and welfare, so National Ambient Air Quality Standards (NAAQS) have been established for each. As of 2013, over 100 million people in the U.S. lived in areas with ozone concentrations above the NAAQS.

NO_x emissions from the power sector, roughly 12% of total NO_x emissions, are and will be significant contributors to ozone concentrations in the U.S. As such, states have reduced peak ozone concentrations through technology-based standards and cap-and-trade programs on NO_x emissions from the power sector. These policies have largely treated NO_x emissions uniformly. But marginal damages from NO_x emissions are greatest on hot sunny days when meteorological conditions favor high ozone formation rates and, consequently, peak ozone concentrations.

This thesis informs what type of policy is the most efficient for reducing peak ozone concentrations on high ozone days by assessing the cost-effectiveness of three policies for reducing NO_x emissions on high ozone days. Emissions and costs under a relatively-novel differentiated policy, time-differentiated pricing, are compared for the first time to two currently-implemented undifferentiated policies, cap-and-trade and technology-based standards. Two power systems are studied, Texas and the Mid-Atlantic. A unique two-phase model is developed to capture the short- (redispatching) and long-term (control technology installation) effects of pricing schemes on power plants. The two-phase model dispatches generators with a unit commitment model, which, unlike past studies, captures real-world operational constraints of generators that may strongly influence emissions and costs under time-differentiated pricing. Technology-based standards are simulated via Monte Carlo analysis to capture the uncertain rulemaking process.

For reducing NO_x emissions on high ozone days in both power systems, time-differentiated pricing is shown to be the most cost-effective policy with regards to producer and consumer costs. Most emissions reductions are due to substitution of gas- for coal-fired generators, as control technology installations are only observed at very high time-differentiated prices. For reducing summer-wide NO_x emissions, undifferentiated pricing is the most cost-effective. In a minority of allocations, technology-based standards also achieve more cost-effective summer-wide reductions than time-differentiated pricing, but such allocations cannot be guaranteed ex ante. These results suggest that time-differentiated pricing is the most efficient policy for reducing peak ozone concentrations, depending on ozone formation rates.

Passenger vehicles and power plants are major sources of greenhouse gas emissions. While economic analyses generally indicate that a broader market-based approach to greenhouse gas reduction would be less costly and more effective, regulatory approaches have found greater political success. Vehicle efficiency standards have a long history in the U.S and elsewhere, and the recent success of shale gas in the U.S. leads to a focus on coal–gas fuel switching as a way to reduce power sector emissions. We evaluate a global regulatory regime that replaces coal with natural gas in the electricity sector and imposes technically achievable improvements in the efficiency of personal transport vehicles. Its performance and cost are compared with other scenarios of future policy development including a no policy world, achievements under the Copenhagen accord, and a price-based policy to reduce global emissions by 50% by 2050. The assumed regulations applied globally achieve a global emissions reduction larger than projected for the Copenhagen agreements, but they do not prevent global GHG emissions from continuing to grow, and the reduction in emissions is achieved at a high cost compared to a price-based policy. Diagnosis of the reasons for the limited yet high-cost performance reveals influences including the partial coverage of emitting sectors, small or no influence on the demand for emissions-intensive products, leakage when a reduction in fossil use in the covered sectors lowers the price to others, and the partial coverage of GHGs.

Adequate quantification of evapotranspiration (ET) is crucial to assess how climate change and land cover change (LCC) interactwith the hydrological cycle of terrestrial ecosystems. The Mongolian Plateau plays a unique role in the global climate system due to its ecological vulnerability, high sensitivity to climate change and disturbances, and limited water resources. Here, we used a version of the Terrestrial Ecosystem Model that has been modified to use Penman–Monteith (PM) based algorithms to calculate ET. Comparison of site-level ET estimates from the modified model with ET measured at eddy covariance (EC) sites showed better agreement than ET estimates from the MODIS ET product, which overestimates ET during the winter months. The modified model was then used to simulate ET during the 21st century under six climate change scenarios by excluding/including climate-induced LCC. We found that regional annual ET varies from 188 to 286 mm yr−1 across all scenarios, and that it increases between 0.11 mm yr−2 and 0.55 mm yr−2 during the 21st century. A spatial gradient of ET that increases fromthe southwest to the northeast is consistent in all scenarios. Regional ET in grasslands, boreal forests and semi-desert/deserts ranges from 242 to 374 mm yr−1, 213 to 278 mm yr−1 and 100 to 199 mm yr−1, respectively; and the degree of the ET increase follows the order of grassland, semi-desert/desert, and boreal forest. Across the plateau, climate-induced LCC does not lead to a substantial change (b5%) in ET relative to a static land cover, suggesting that climate change ismore important than LCC in determining regional ET. Furthermore, the differences between precipitation and ET suggest that the available water for human use (water availability) on the plateau will not change significantly during the 21st century. However, more water is available and less area is threatened by water shortage in the Business-As-Usual emission scenarios relative to level-one stabilization emission scenarios.

© 2013 Elsevier B.V.

We used a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to examine the methane (CH4) exchanges between terrestrial ecosystems and the atmosphere in Northern Eurasia from 1971 to 2100. Multiple model simulations using various wetland extent datasets and climate change scenarios were conducted to assess the uncertainty of CH4 fluxes, including emissions and consumption. On the basis of these simulations we estimate the current net emissions in the region to be 20–24 Tg CH4 yr − 1 (1 Tg = 1012 g), two-thirds of which are emitted during the summer. In response to climate change over the 21st century, the annual CH4 emissions in the region are projected to increase at a rate of 0.06 Tg CH4 yr − 1, which is an order of magnitude greater than that of annual CH4 consumption. Further, the annual net CH4 emissions are projected to increase by 6–51% under various wetland extent datasets and climate scenarios by the end of the 21st century, relative to present conditions. Spatial patterns of net CH4 emissions were determined by wetland extent. Net CH4 emissions were dominated by wetlands within boreal forests, grasslands and wet tundra areas in the region. Correlation analyses indicated that water table depth and soil temperature were the two most important environmental controls on both CH4 emissions and consumption in the region. Our uncertainty analyses indicated that the uncertainty in wetland extent had a larger effect on future CH4 emissions than the uncertainty in future climate. This study suggests that better characterization of the spatial distribution and the natural diversity of wetlands should be a research priority for quantifying CH4 fluxes in this region.

© 2011 IOP Publishing Ltd.