Air quality co-benefits can potentially reduce the costs of greenhouse gas mitigation. However, while many studies of the cost of greenhouse gas mitigation model the full macroeconomic welfare impacts, most studies of air quality co-benefits do not. We employ a US computable general equilibrium economic model previously linked to an air quality modeling system, and enhance it to represent the economy-wide welfare impacts of fine particulate matter. We present a first application of this method to explore the efficiency and the distributional implications of a clean energy standard (CES) and a cap–and–trade (CAT) program that both reduce CO2 emission by 10% in 2030 relative to 2006. We find that co-benefits from fine particulate matter reduction completely offset policy costs by 110% (40% to 190%), transforming the net welfare impact of the CAT into a gain of $1 (-$5 to $7) billion 2005 US$. For the CES, the corresponding co-benefit (median $8; $3 to $14)/tCO2 is a smaller fraction (median 5%; 2% to 9%) of its higher policy cost. The eastern US garners 78% and 71% of co-benefits for the CES and CAT, respectively. By representing the effects of pollution-related morbidities and mortalities as an impact to labor and the demand for health services, we find that the welfare impact per unit of reduced pollution varies by region. These interregional differences can enhance the preference of some regions, like Texas, for a CAT over a CES, or switch the calculation of which policy yields higher co-benefits, compared to an approach that uses one valuation for all regions. This framework could be applied to quantify consistent air quality impacts of other pricing instruments, subnational trading programs, or green tax swaps.

We present a model of diverse phytoplankton and zooplankton populations embedded in a global ocean circulation model. Physiological and ecological traits of the organisms are constrained by relationships with cell size. The model qualitatively reproduces global distributions of nutrients, biomass, and primary productivity, and captures the power-law relationship between cell size and numerical density, which has realistic slopes of between 21.3 and 20.8. We use the model to explore the global structure of marine ecosystems, highlighting the importance of both nutrient and grazer controls. The model suggests that zooplankton : phytoplankton (Z : P) biomass ratios may vary from an order of 0.1 in the oligotrophic gyres to an order of 10 in upwelling and highlatitude regions. Global estimates of the strength of bottom-up and top-down controls within plankton size classes suggest that these large-scale gradients in Z : P ratios are driven by a shift from strong bottom-up, nutrient limitation in the oligotrophic gyres to the dominance of top-down, grazing controls in more productive regions.

© 2012 Association for the Science of Limnology and Oceanography

With the risks of climate change becoming increasingly evident, there is growing discussion regarding international treaties and national regulations to lower greenhouse gas (GHG) emissions. Enforcement of such agreements is likely to depend formally upon national and sectoral emission reporting procedures (sometimes referred to as “bottom-up” methods). However, for these procedures to be credible and effective, it is essential that these reports or claims be independently verified. In particular, any disagreements between these “bottom-up” emission estimates, and independent emission estimates inferred from global GHG measurements (so-called “top-down” methods) need to be resolved. Because emissions control legislation is national or regional in nature, not global, it is also essential that “top-down” emission estimates be determined at these same geographic scales. This report lays out a strategy for quantifying and reducing uncertainties in greenhouse gas emissions, based on a comprehensive synthesis of global observations of various types with models of the global cycles of carbon dioxide and other greenhouse gases that include both the natural and human influences on these cycles. The overall goal is to establish a global observing and estimation system that incorporates all relevant available knowledge (physical, biogeochemical, technological and economic) in order to verify greenhouse gas emissions, as a key component of any global GHG treaty. 

Because human activities emit greenhouse gases (GHGs) and conventional air pollutants from common sources, policy designed to reduce GHGs can have co-benefits for air quality that may offset some or all of the near-term costs of GHG mitigation. We present a systems approach to quantify air quality co-benefits of US policies to reduce GHG (carbon) emissions. We assess health-related benefits from reduced ozone and particulate matter (PM_2.5) by linking three advanced models, representing the full pathway from policy to pollutant damages. We also examine the sensitivity of co-benefits to key policy-relevant sources of uncertainty and variability. We find that monetized human health benefits associated with air quality improvements can offset 26-1050% of the cost of U.S. carbon policies. More flexible policies that minimize costs, such as cap-and-trade standards, have larger net co-benefits than policies that target specific sectors (electricity and transportation). While air quality co-benefits can be comparable with policy costs for present-day air quality and near-term U.S. carbon policies, potential co-benefits rapidly diminish as carbon policies become more stringent.

© 2014 Nature Publishing Group