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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.

Combining Price and Quantity Controls under Partitioned Environmental Regulation

This paper analyzes hybrid emissions trading systems (ETS) under partitioned environmental regulation when firms’ abatement costs and future emissions are uncertain. We show that hybrid policies that introduce bounds on the price or the quantity of abatement provide a way to hedge against differences in marginal abatement costs across partitions. Price bounds are more efficient than abatement bounds as they also use information on firms’ abatement technologies while abatement bounds can only address emissions uncertainty. Using a numerical stochastic optimization model with equilibrium constraints for the European carbon market, we find that introducing hybrid policies in EU ETS reduces expected excess abatement costs of achieving targeted emissions reductions under EU climate policy by up to 89 percent. We also find that under partitioned regulation there is a high likelihood for hybrid policies to yield sizeable ex-post cost reductions.

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

Contribution of biomass to emissions abatement under a global carbon policy

What will large-scale global bioenergy production look like? We investigate this question by developing a detailed representation of bioenergy production and use in a global economy-wide model. To create market conditions favorable to biomass energy, we develop a scenario with a global carbon dioxide price that starts at $55 per ton in 2015 and rises to $217 in 2050, which results in a global bioenergy production of ~140 exajoules (EJ) in 2050. By comparison, in 2010 global coal energy was 139 EJ, oil 175 EJ, and gas 108 EJ. In our simulations, there is a short-term role for first-generation biofuels, but lignocellulosic biofuels are the largest component of bioenergy by 2050. This results reflects our assumptions that there is the most potential for cost-reducing technical advance in this process, combined with the fact that land requirements to grow cellulosic feedstocks are lower than for conventional crops. Biomass also competes favorably to supply industrial process heat. Even at this large scale, we find that land requirements for bioenergy production do not result in significant land-use change issues. The availability of biomass residues, increasing interests in limiting deforestation, and improvements in crop yields and efficiency in converting biomass to energy combine to reduce pressure on land markets.

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.

Costs of reducing GHG emissions in Brazil

During the 2009 Conference of the Parties meeting in Copenhagen, the Brazilian government announced voluntary targets to reduce GHG emissions, with the targets being reconfirmed in Cancun (2010) and in Durban (2011). An estimate is presented of the economic impact of alternative policies to achieve such targets, including actions to cut emissions from deforestation and agricultural production. A dynamic-recursive general equilibrium model of the world economy is used. The main results show that deforestation emissions in Brazil can be reduced at very low costs, but the cost of cutting emissions from agriculture and energy use may lead to a 2.3% drop in gross domestic product by 2020 if sector-specific carbon taxes are applied. Such costs may be reduced to 1.5% under a carbon trading scheme. The negative impact of carbon taxes on agricultural production indirectly reduces deforestation rates; therefore, directly cutting emissions from deforestation is the most cost-effective option since it does not adversely affect agricultural production, which continues to expand into low-yield, underutilized pastures and secondary forest areas.

Cross-country electricity trade, renewable energy and European transmission infrastructure policy

This paper develops a multi-country multi-sector general equilibrium model, integrating high-frequency electricity dispatch and trade decisions, to study the effects of electricity transmission infrastructure (TI) expansion and renewable energy (RE) penetration in Europe for gains from trade and carbon dioxide emissions in the power sector. TI can benefit or degrade environmental outcomes, depending on RE penetration: it complements emissions abatement by mitigating dispatch problems associated with volatile and spatially dispersed RE but also promotes higher average generation from low-cost coal if RE production is too low. Against the backdrop of European decarbonization and planned TI expansion, we find that emissions increase for current and targeted year-2020 levels of RE production and decrease for year-2030 targets. Enhanced TI yields sizeable gains from trade that depend positively on RE penetration, without creating large adverse impacts on regional equity.

Determinants of Crop Yield and Profit of Family Farms: Evidence from the Senegal River Valley

This paper investigates the determinants of the performance of family farms in Senegal using both production and profit functions. The econometric analysis is based on agricultural inputs and outputs information from a survey of 504 agricultural households, member of a farmer organization in the Saint Louis region in 2009. Our main results indicate that the size of the cultivated plots has a negative effect on crop yields, representing diseconomies of scale. This finding suggests potential for improvements in farm management and organization. We also find that the development of commercialization sectors and loans could boost agricultural inputs. In terms of profitability, our results show that yields and prices play significant and important roles for all crops. An increase in the bargaining power of farmers would be required to increase unit prices and consequently their profits.

© 2016 Cambridge University Press

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