This paper introduces endogenous and directed technical change in a growth model with environmental constraints and limited resources. A unique final good is produced by combining inputs from two sectors. One of these sectors uses "dirty" machines and thus creates environmental degradation. Research can be directed to improving the technology of machines in either sector. We characterize dynamic tax policies that achieve sustainable growth or maximize intertemporal welfare, as a function of the degree of substitutability between clean and dirty inputs, environmental and resource stocks, and cross-country technological spillovers. We show that: (i) in the case where the inputs are sufficiently substitutable, sustainable long-run growth can be achieved with temporary taxation of dirty innovation and production; (ii) optimal policy involves both "carbon taxes" and research subsidies, so that excessive use of carbon taxes is avoided; (iii) delay in intervention is costly: the sooner and the stronger is the policy response, the shorter is the slow growth transition phase; (iv) the use of an exhaustible resource in dirty input production helps the switch to clean innovation under laissez-faire when the two inputs are substitutes. Under reasonable parameter values (corresponding to those used in existing models with exogenous technology) and with sufficient substitutability between inputs, it is optimal to redirect technical change towards clean technologies immediately and optimal environmental regulation need not reduce long-run growth. We also show that in a two-country extension, even though optimal environmental policy involves global policy coordination, when the two inputs are sufficiently substitutable environmental regulation only in the North may be sufficient to avoid a global disaster.

/pdf/the-environment-and-directed-technical-change-2kjjoszm1x.pdf

The Environment and Directed Technical Change

. In this study, 121 daily PM2.5 (aerosol particle with aerodynamic diameter less than 2.5 μm) samples were collected from an urban site in Beijing in four months between April 2009 and January 2010 representing the four seasons. The samples were determined for various compositions, including elements, ions, and organic/elemental carbon. Various approaches, such as chemical mass balance, positive matrix factorization (PMF), trajectory clustering, and potential source contribution function (PSCF), were employed for characterizing aerosol speciation, identifying likely sources, and apportioning contributions from each likely source. Our results have shown distinctive seasonality for various aerosol speciations associated with PM2.5 in Beijing. Soil dust waxes in the spring and wanes in the summer. Regarding the secondary aerosol components, inorganic and organic species may behave in different manners. The former preferentially forms in the hot and humid summer via photochemical reactions, although their precursor gases, such as SO2 and NOx, are emitted much more in winter. The latter seems to favorably form in the cold and dry winter. Synoptic meteorological and climate conditions can overwhelm the emission pattern in the formation of secondary aerosols. The PMF model identified six main sources: soil dust, coal combustion, biomass burning, traffic and waste incineration emission, industrial pollution, and secondary inorganic aerosol. Each of these sources has an annual mean contribution of 16, 14, 13, 3, 28, and 26%, respectively, to PM2.5. However, the relative contributions of these identified sources significantly vary with changing seasons. The results of trajectory clustering and the PSCF method demonstrated that regional sources could be crucial contributors to PM pollution in Beijing. In conclusion, we have unraveled some complex aspects of the pollution sources and formation processes of PM2.5 in Beijing. To our knowledge, this is the first systematic study that comprehensively explores the chemical characterizations and source apportionments of PM2.5 aerosol speciation in Beijing by applying multiple approaches based on a completely seasonal perspective.

/pdf/chemical-characterization-and-source-apportionment-of-pm-2-5-3q6oghogl3.pdf

Chemical characterization and source apportionment of PM 2.5 in Beijing: seasonal perspective

This memorandum documents the updates implemented in EPA’s 2020 Inventory of U.S. Greenhouse Gas Emissions and Sinks (GHGI) for gathering and boosting (G&B) stations. Additional considerations for G&B were previously discussed in memoranda released November 2019 (Inventory of U.S. Greenhouse Gas Emissions and Sinks 1990-2018: Updates Under Consideration for Natural Gas Gathering & Boosting Station Emissions),1 October 2018 (Inventory of U.S. GHG Emissions and Sinks 1990-2017: Updates Under Consideration for Natural Gas Gathering & Boosting Emissions),2 and April 2019 (Inventory of U.S. GHG Emissions and Sinks 1990-2017: Updates to Natural Gas Gathering & Boosting Pipeline Emissions).3

Inventory of U.S. Greenhouse Gas Emissions and Sinks

The field of atmospheric chemistry is very broad, both in the problems addressed and in the approaches taken. Thus, it includes laboratory and theoretical studies, field measurements, and modeling, and addresses chemistry from the lower to the upper atmosphere, in remote and polluted regions, from marine to continental areas, and both outdoors and indoors. Given this complexity, it is impossible to capture all aspects with the limited number of articles that can be included in a special feature. Thus, what follows should be taken as illustrative rather than inclusive.

The genesis of the field of atmospheric chemistry lies in air pollution in the troposphere (lower atmosphere), for which there is documentation at least as long ago as the 13th century. Dramatic incidents of excess deaths such as in the Meuse Valley, Belgium, in 1930 (1), and in London, England, in 1952 (2) brought public and scientific attention to “smog” (smog = smoke + fog) and, in particular, to the problem of sulfur dioxide and sulfate particles it forms in air, as well as to direct emissions of particles from combustion sources. Around 1950, what initially appeared to be a different kind of smog, now known as photochemical air pollution, was recognized in the Los Angeles area. The seminal work of Haagen-Smit demonstrated that the necessary ingredients (primary pollutants) were volatile organic compounds (VOC), oxides of nitrogen (NOx = NO + NO2), and sunlight. The wavelengths available to drive photochemistry at the earth's surface are restricted to … 

1E-mail: bjfinlay{at}uci.edu.

https://www.pnas.org/content/pnas/107/15/6566.full.pdf

Atmospheric chemistry

Energy efficiency and conservation are major factors in the reduction of the environmental impact of the energy sector, particularly with regard to climate change. Energy efficiency also contributes to reducing external dependence and vulnerabilities in the energy domain. In this paper, we discuss the factors that influence energy efficiency and conservation decisions, and the most appropriate policies for their promotion. Although not all public policies seem justified, we argue that specific policies for promoting energy conservation may be required, preferably based on economic instruments or on the provision of information to consumers.

/pdf/energy-efficiency-economics-and-policy-2s6ucoafb1.pdf

F. B Mitchell

Papers

A contribution of Working Groups I, II and III to the Third Assessment Report of the Intergovernment Panel on Climate Change