1998: Trends in Tropospheric Aerosol Forcing 1950-1990

Researchers: Susane Colasanti, Thomas Ferede, Tariq Jones, Ben Lewis, Anthony Luckett, Courtney St. Prix, and Ina Tegen.

The Aerosol Emissions project began in summer 1998 as a part of the Forcings and Chaos research team. The tropospheric aerosol forcing for the years 1950 to present needs to be included into the GISS GCM for the Forcing and Chaos investigation. Aerosols are reflecting (and absorbing) incoming solar radiation. This process might offset the warming trend caused by increases in greenhouse gases in industrialized regions like the eastern US. Tropospheric aerosols consist of different species with different optical properties, which need to be considered separately.

Project Goal for 1998-99

The team will investigate the trends of sulfate (non-absorbing) and black carbon (absorbing) aerosols from anthropogenic fossil fuel burning sources. Once emission scenarios are defined for the individual species, transport-chemistry models are used to compute their global distributions, which need to be converted into optical thickness in order to calculate their radiative effect and climate response to their forcing. Since those calculations depend on the reliability of the emission scenarios, this project will evaluate methods to estimate emission scenarios for sulfur and black carbon (BC) for the period 1950 to 1990 and compare those to existing emission scenarios for the year 1985.

Science Questions

1. Can a simple method for the estimation of SO₂ and BC emissions be used to calculate realistic trends from fossil fuel emissions?
2. Did environmental policies across the globe have an effect on emissions?
3. How did the distribution of SO₂ and BC change in different parts of the world?
4. What information can we derive from this on the composition of tropospheric aerosols for the years 1950 to present?
5. How are sulfur and nitrogen emitted into the atmosphere? How are they changed into SO_x and NO_x?

Hypothesis

A derived Global emissions scenario can be used to reproduce a realistic trend in the radiative forcing of SO₂ and black carbon aerosols.

Research Tasks

1. Repeat the calculation of Dignon/Hameed to find the parameters of the fit between solid and liquid fuel and SO₂ (NO_x) emissions.
2. Compare the results for the year 1985 from the Dignon/Hameed method with the Global Emissions Inventory Activity (GEIA) emission scenario to decide whether this method gives a sufficiently good approximation of SO₂ (NO_x)emissions.
3. Extend the Dignon/Hameed method with data later than 1982. Compare the period from 1970-1982 to1982-1985.
4. Calculate the emissions scenarios using the new fit parameters. Compare the results to results obtained from directly applying SO₂ (NO_x) emissions trends in countries where such trends are available.
5. From the ASL database, plot emission trends for some individual countries.
6. Compare the results of the ASL database with those given in the GEIA inventory for the years 1985 and 1990.
7. Use a table of maximum and minimum sulfur content to calculate the range of possible uncertainty of the sulfur emissions for countries whose trends were plotted.
8. Compare the black carbon emission scenarios from Cooke and Wilson (1996) and Penner (1993).
9. Using UN statistics database for the consumption of diesel oil, hard coal and brown coal, test whether the black carbon emission scenario from GEIA can be reproduced for 1985. This comparison will be done for several typical countries eg. USA, China, and the European block.
10. Given that the previous comparison is successful, use UN statistics to construct emission trends for the period 1950 to present. If time permits, this should be done for the whole globe.
11. From trend in SO₂ and BC emissions, get estimate via "back of the envelope". Estimate on change in aerosol composition, optical thickness, and ultimately in direct radiative forcing.

Data

ASL/CAPITA. This global database contains regional sulfate emission data for 1850-1990 which was derived from fuel consumption data and estimates. This data took into account the percentages of sulfur in fuels and metals, and retention factors based on technological removal of sulfur. The database reports sulfur emissions resulting from the consumption of hard coal, brown coal, oil and smelting processes.

GEIA. This database is a global inventory of SO₂ emissions from anthropogenic sources. In order to make the inventory useful for modeling atmospheric transport, transformation and removal the emissions were allocated to a 1° × 1° longitude/latitude grid for the year 1985.

/u7/pinatubo/ina/summer98/CDIAC/nation95.ems; 1800-present. This data set is comprised of CO₂ emissions estimates from the combustion of fossil fuels, manufacturing of cement, and gas flaring for the countries of the world. The estimates are categorized by nature (i.e. solid, liquid), and are expressed in units of thousand metric tons of carbon (C) per year.

National air pollutant trends 1900-1996; EPA. This data is divided into Source categories: Fuel Combustion (electrical utility, industrial, other), Chemical and Allied Product MFG, etc. The emissions are given in terms of thousand short tons (a short ton = 2000lbs). The short tons were converted to metric tons (a factor of 0.9072). The total emissions for the decade years (1940, 50, 60, 70, 80, 90) data are given.

Since the Dignon/Hameed method expresses results in coal equivalent, the data above is multiplied by a coal equivalent constant.

/u7/pintubo/ina/summer98/GEIA/antbc84yr1.1x1.-t. This is a database of global black carbon emissions. Black carbon emissions are calculated using fuel production and trade data, and efficiency estimates per amount of fuel consumed. The data is given in a 1° × 1° format and uses 23 different fuel types to determine emissions. Some biomass burning is included in the calculations (1984).

/u7/pintubo/ina/summer98/GEIA/blc85yr1.1x1-t. This is a database of global black carbon emissions. The database determines black carbon emissions through black carbon/sulfur ratios taken across the globe. It uses a data set of sulfur emissions which is assumed to be accurate. The data is given in 1° × 1° format (1985).

/u7/pintubo/ina/summer98/UNstat/. This is a database put together by the United Nations comprising of energy statistics on more than 215 countries. It contains data for production, trade, consumption, conventional and non-conventional, new and renewable sources of energy.