Regional Analysis

Changes in Inorganic Fine Particulate Matter Sensitivities to Precursors Due to Large-Scale US Emissions Reductions

We examined the impact of large US emissions changes, similar to those estimated to have occurred between 2005 and 2012 (high and low emissions cases, respectively), on inorganic PM2.5 sensitivities to further NOx, SO2, and NH3 emissions reductions using the chemical transport model GEOS-Chem. Sensitivities to SO2 emissions are larger year-round and across the US in the low emissions case than the high emissions case due to more aqueous-phase SO2 oxidation. Sensitivities to winter NOx emissions are larger in the low emissions case, more than 2x those of the high emissions case in parts of the northern Midwest. Sensitivities to NH3 emissions are smaller (∼40%) in the low emissions case, year-round, and across the US. Differences in NOx and NH3 sensitivities indicate an altered atmospheric acidity. Larger sensitivities to SO2 and NOx in the low emissions case imply that reducing these emissions may improve air quality more now than they would have in 2005; conversely, NH3 reductions may not improve air quality as much as previously assumed.

© 2015 American Chemical Society

Climate change impacts and greenhouse gas mitigation effects on U.S. water quality

Climate change will have potentially significant effects on freshwater quality due to increases in river and lake temperatures, changes in the magnitude and seasonality of river runoff, and more frequent and severe extreme events. These physical impacts will in turn have economic consequences through effects on riparian development, river and reservoir recreation, water treatment, harmful aquatic blooms, and a range of other sectors. In this paper, we analyze the physical and economic effects of changes in freshwater quality across the contiguous U.S. in futures with and without global-scale greenhouse gas mitigation. Using a water allocation and quality model of 2119 river basins, we estimate the impacts of various projected emissions outcomes on several key water quality indicators, and monetize these impacts with a water quality index approach. Under mitigation, we find that water temperatures decrease considerably and that dissolved oxygen levels rise in response. We find that the annual economic impacts on water quality of a high emissions scenario rise from $1.4 billion in 2050 to $4 billion in 2100, leading to present value mitigation benefits, discounted at 3%, of approximately $17.5 billion over the 2015–2100 period.

© 2015 the authors

 

Climate Change Impacts on U.S. Crops

The Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment Report (AR5) (Romero-Lankao et al., 2014) found that climate change is responsible in part for historical yield increases in the United States thanks to increased precipitation. Since 1999, however, yield losses have been attributed to extreme weather events, such as heat waves, storms, and droughts and the IPCC concludes that in many crop growing regions of North America optimum temperatures have been reached and further warming would be detrimental to crop yields. What to expect in the future?

© 2015 CHOICES

Climate change policy in Brazil and Mexico: Results from the MIT EPPA model

Based on an in-depth analysis of results from the MIT Economic Projection and Policy Analysis (EPPA) model of climate policies for Brazil and Mexico, we demonstrate that commitments by Mexico and Brazil for 2020—made during the UN climate meetings in Copenhagen and Cancun—are reachable, but they come at different costs for each country. We find that Brazil's commitments will be met through reduced deforestation, and at no additional cost; however, Mexico's pledges will cost 4 billion US dollars in terms of reduced GDP in 2020. We explore short- and long-term implications of several policy scenarios after 2020, considering current policy debates in both countries. The comparative analysis of these two economies underscores the need for climate policy designed for the specific characteristics of each country, accounting for variables such as natural resources and current economic structure. Our results also suggest that both Brazil and Mexico may face other environmental and economic impacts from stringent global climate policies, affecting variables such as the value of energy resources in international trade.

© 2015 The Authors.

Climate Change, Water Resources and Irrigated Crop Yields: A Modeling Framework for Integrated Assessment of the US

While the impact of climate change on rainfed crop yields has been extensively studied, the study of the effect on irrigated crop yields has been more challenging due to competing water uses. By combining a water model and a crop model within the MIT Integrated Global System Model (IGSM) framework (Sokolov et al., 2005), an integrated assessment of the effects of alternative climate policy scenarios on irrigated crop yields is applied to the United States (US). In this analysis, we consider the effect of water shortage for irrigation on the three most important crops for the U.S.: maize, soybean and spring wheat. We find that water shortage for irrigation is expected to reduce irrigated crop yields especially for maize.

Climate extremes and ozone pollution: a growing threat to China's food security

Ensuring global food security requires a sound understanding of climate and environmental controls on crop productivity. The majority of existing assessments have focused on physical climate variables (i.e., mean temperature and precipitation), but less on the increasing climate extremes (e.g., drought) and their interactions with increasing levels of tropospheric ozone (O3). Here we quantify the combined impacts of drought and O3 on China's crop yield using a comprehensive, process-based agricultural ecosystem model in conjunction with observational data. Our results indicate that climate change/variability and O3 together led to an annual mean reduction of crop yield by 10.0% or 55 million tons per year at the national level during 1981–2010. Crop yield shows a growing threat from severe episodic droughts and increasing O3 concentrations since 2000, with the largest crop yield losses occurring in northern China, causing serious concerns in food supply security in China. Our results imply that reducing tropospheric O3 levels is critical for securing crop production in coping with increasing frequency and severity of extreme climate events such as droughts. Improving air quality should be a core component of climate adaptation strategies.

Climate Policy Scenarios in Brazil: A Multi-Model Comparison for Energy

This paper assesses the effects of market-based mechanisms and carbon emission restrictions on the Brazilian energy system by comparing the results of six different energy-economic or integrated assessment models under different scenarios for carbon taxes and abatement targets up to 2050. Results show an increase over time in emissions in the baseline scenarios due, largely, to higher penetration of natural gas and coal. Climate policy scenarios, however, indicate that such a pathway can be avoided. While taxes up to 32 US$/tCO2e do not significantly reduce emissions, higher taxes (from 50 US$/tCO2e in 2020 to 16 2US$/tCO2e in 2050) induce average emission reductions around 60% when compared to the baseline. Emission constraint scenarios yield even lower reductions in most models. Emission reductions are mostly due to lower energy consumption, increased penetration of renewable energy (especially biomass and wind) and of carbon capture and storage technologies for fossil and/or biomass fuels. This paper also provides a discussion of specific issues related to mitigation alternatives in Brazil. The range of mitigation options resulting from the model runs generally falls within the limits found for specific energy sources in the country, although infrastructure investments and technology improvements are needed for the projected mitigation scenarios to achieve actual feasibility.

Constraints from observations and modeling on atmosphere–surface exchange of mercury in eastern North America

Atmosphere–surface exchange of mercury, although a critical component of its global cycle, is currently poorly constrained. Here we use the GEOS-Chem chemical transport model to interpret atmospheric Hg0 (gaseous elemental mercury) data collected during the 2013 summer Nitrogen, Oxidants, Mercury and Aerosol Distributions, Sources and Sinks (NOMADSS) aircraft campaign as well as ground- and ship-based observations in terms of their constraints on the atmosphere–surface exchange of Hg0 over eastern North America. Model–observation comparison suggests that the Northwest Atlantic may be a net source of Hg0, with high evasion fluxes in summer (our best sensitivity simulation shows an average oceanic Hg0 flux of 3.3 ng m-2 h-1 over the Northwest Atlantic), while the terrestrial ecosystem in the summer of the eastern United States is likely a net sink of Hg0 (our best sensitivity simulation shows an average terrestrial Hg0 flux of -0.6 ng m-2 h-1 over the eastern United States). The inferred high Hg0 fluxes from the Northwest Atlantic may result from high wet deposition fluxes of oxidized Hg, which are in turn related to high precipitation rates in this region. We also find that increasing simulated terrestrial fluxes of Hg0 in spring compared to other seasons can better reproduce observed seasonal variability of Hg0 concentration at ground-based sites in eastern North America.

Consumption-Based Adjustment of Emissions-Intensity Targets: An Economic Analysis for China's Provinces

China’s Twelfth Five-Year Plan (2011–2015) aims to achieve a national carbon intensity reduction of 17 % through differentiated targets at the provincial level. Allocating the national target among China’s provinces is complicated by the fact that more than half of China’s national carbon emissions are embodied in interprovincial trade, with the relatively developed eastern provinces relying on the center and west for energy-intensive imports. This study develops a consistent methodology to adjust regional emissions-intensity targets for trade-related emissions transfers and assesses its economic effects on China’s provinces using a regional computable-general-equilibrium (CGE) model of the Chinese economy. This study finds that in 2007 China’s eastern provinces outsource 14 % of their territorial emissions to the central and western provinces. Adjusting the provincial targets for those emissions transfers increases the reduction burden for the eastern provinces by 60 %, while alleviating the burden for the central and western provinces by 50 % each. The CGE analysis indicates that this adjustment could double China’s national welfare loss compared to the homogenous and politics-based distribution of reduction targets. A shared-responsibility approach that balances production-based and consumption-based emissions responsibilities is found to alleviate those unbalancing effects and lead to a more equal distribution of economic burden among China’s provinces.

© 2014 Springer Science+Business Media

Costs of IQ Loss from Leaded Aviation Gasoline Emissions

In the United States, general aviation piston-driven aircraft are now the largest source of lead emitted to the atmosphere. Elevated lead concentrations impair children’s IQ and can lead to lower earnings potentials. This study is the first assessment of the nationwide annual costs of IQ losses from aircraft lead emissions. We develop a general aviation emissions inventory for the continental United States and model its impact on atmospheric concentrations using the community multi-scale air quality model (CMAQ). We use these concentrations to quantify the impacts of annual aviation lead emissions on the U.S. population using two methods: through static estimates of cohort-wide IQ deficits and through dynamic economy-wide effects using a computational general equilibrium model. We also examine the sensitivity of these damage estimates to different background lead concentrations, showing the impact of lead controls and regulations on marginal costs. We find that aircraft-attributable lead contributes to $1.06 billion 2006 USD ($0.01–$11.6) in annual damages from lifetime earnings reductions, and that dynamic economy-wide methods result in damage estimates that are 54% larger. Because the marginal costs of lead are dependent on background concentration, the costs of piston-driven aircraft lead emissions are expected to increase over time as regulations on other emissions sources are tightened.

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