Adjoint estimation of ozone climate penalties

An adjoint of a regional chemical transport model is used to calculate location-specific temperature influences (climate penalties) on two policy-relevant ozone metrics: concentrations in polluted regions (>65 ppb) and short-term mortality in Canada and the U.S. Temperature influences through changes in chemical reaction rates, atmospheric moisture content, and biogenic emissions exhibit significant spatial variability. In particular, high-NO x, polluted regions are prominently distinguished by substantial climate penalties (up to 6.2 ppb/K in major urban areas) as a result of large temperature influences through increased biogenic emissions and nonnegative water vapor sensitivities. Temperature influences on ozone mortality, when integrated across the domain, result in 369 excess deaths/K in Canada and the U.S. over a summer season - an impact comparable to a 5% change in anthropogenic NOx emissions. As such, we suggest that NOx control can be also regarded as a climate change adaptation strategy with regard to ozone air quality. Key Points Ozone climate penalties in North America show great spatial variability High-NOx regions are among locations with the largest climate penalties NOx control can be seen as a climate change adap

Improving NO_<i>x</i> Cap-and-Trade System with Adjoint-Based Emission Exchange Rates

Cap-and-trade programs have proven to be effective instruments for achieving environmental goals while incurring minimum cost. The nature of the pollutant, however, affects the design of these programs. NO_<i>x</i>, an ozone precursor, is a nonuniformly mixed pollutant with a short atmospheric lifetime. NO_<i>x</i> cap-and-trade programs in the U.S. are successful in reducing total NO_<i>x</i> emissions but may result in suboptimal environmental performance because location-specific ozone formation potentials are neglected. In this paper, the current NO_<i>x</i> cap-and-trade system is contrasted to a hypothetical NO_<i>x</i> trading policy with sensitivity-based exchange rates. Location-specific exchange rates, calculated through adjoint sensitivity analysis, are combined with constrained optimization for prediction of NO_<i>x</i> emissions trading behavior and post-trade ozone concentrations. The current and proposed policies are examined in a case study for 218 coal-fired power plants that participated in the NO_<i>x</i> Budget Trading Program in 2007. We find that better environmental performance at negligibly higher system-wide abatement cost can be achieved through inclusion of emission exchange rates. Exposure-based exchange rates result in better environmental performance than those based on concentrations

Optimal Ozone Control with Inclusion of Spatiotemporal Marginal Damages and Electricity Demand

(Figure Presented) Marginal damage (MD), or damage per ton of emission, is a policy metric used for effective pollution control and reducing the corresponding adverse health impacts. However, for a pollutant such as NOx, the MD varies by the time and location of the emissions, a complication that is not adequately accounted for in the currently implem

Optimal ozone reduction policy design using adjoint-based NOx marginal damage information

Despite substantial reductions in nitrogen oxide (NOx) emissions in the United States, the success of emission control programs in optimal ozone reduction is disputable because they do not consider the spatial and temporal differences in health and environmental damages caused by NOx emissions. This shortcoming in the current U.S. NOx control policy is explored, and various methodologies for identifying optimal NOx emission control strategies are evaluated. The proposed approach combines an optimization platform with an adjoint (or backward)

Improving NOx cap-and-trade system with adjoint-based emission exchange rates

Cap-and-trade programs have proven to be effective instruments for achieving environmental goals while incurring minimum cost. The nature of the pollutant, however, affects the design of these programs. NOx, an ozone precursor, is a nonuniformly mixed pollutant with a short atmospheric lifetime. NOx cap-and-trade programs in the U.S. are successful in reducing total NOx emissions but may result in suboptimal environmental performance because location-specific ozone formation potentials are neglected. In this paper, the current NOx cap-and-trade s

Targeted NOx Emissions Control for Improved Environmental Performance

Nitrogen oxides (NOx) are the main ozone precursors, and NOx control programs in the US have led to substantial reductions in emissions. However, it is unknown whether these programs have optimally reduced ozone concentrations. Current control programs do not account for spatial and temporal specificities of NOx emissions. In this paper, this shortcoming in traditional trading systems is addressed and a methodology for identifying optimal NOx emission control strategies is dev

A temporal NOx emissions trading system: Case study of US power plants

Despite the significant NOx reduction in the past decade, ozone concentrations in the eastern US are in violation of the National Ambient Air Quality Standard (NAAQS). This is because the location- and time-specific effects of NOx emissions on ozone formation have not been taken into consideration under cap-and-trade programs where polluters trade their emission quotas on a one-to-one basis. To account for such effects, a cap-and-trade program can be reformed by inclusion of exchange rates set by the regulator on an hourly basis. We examine the performance of such a reformed cap-and-trade program using a case study of US power plants. Our results indicate that shifting emissions from high-damage hours to low-damage hours can significantly improve the performance of the system

Optimal Ozone Reduction Policy Design Using Adjoint-Based NO_<i>x</i> Marginal Damage Information

Despite substantial reductions in nitrogen oxide (NO_<i>x</i>) emissions in the United States, the success of emission control programs in optimal ozone reduction is disputable because they do not consider the spatial and temporal differences in health and environmental damages caused by NO_<i>x</i> emissions. This shortcoming in the current U.S. NO_<i>x</i> control policy is explored, and various methodologies for identifying optimal NO_<i>x</i> emission control strategies are evaluated. The proposed approach combines an optimization platform with an adjoint (or backward) sensitivity analysis model and is able to examine the environmental performance of the current cap-and-trade policy and two damage-based emissions-differentiated policies. Using the proposed methodology, a 2007 case study of 218 U.S. electricity generation units participating in the NO_<i>x</i> trading program is examined. The results indicate that inclusion of damage information can significantly enhance public health performance of an economic instrument. The net benefit under the policy that minimizes the social cost (i.e., health costs plus abatement costs) is six times larger than that of an exchange rate cap-and-trade policy

Optimal Ozone Control with Inclusion of Spatiotemporal Marginal Damages and Electricity Demand

Marginal damage (MD), or damage per ton of emission, is a policy metric used for effective pollution control and reducing the corresponding adverse health impacts. However, for a pollutant such as NO_<i>x</i>, the MD varies by the time and location of the emissions, a complication that is not adequately accounted for in the currently implemented economic instruments. Policies accounting for MD information would aim to encourage emitters with large MDs to reduce their emissions. An optimization framework is implemented to account for NO_<i>x</i> spatiotemporal MDs calculated through adjoint sensitivity analysis and to simulate power plants’ behavior under emission and simplified electricity constraints. The results from a case study of U.S. power plants indicate that time-specific MDs are high around noon and low in the evening. Furthermore, an emissions reduction of about 40% and a net benefit of about $1200 million can be gained for this subset of power plants if a larger fraction of the electricity demand is supplied by power plants at low-damage times and in low-damage locations. The results also indicate that the consideration of temporal effects in NO_<i>x</i> control policies results in a comparable net benefit to the consideration of spatial or spatiotemporal effects, thus providing a promising option for policy development