With growing concern about climatic changes that could result from increased atmospheric carbon dioxide, it is appropriate to use the improved statistics on the production and use of fossil fuels which are now available and to review the CO, discharges to the atmosphere from fossil fuel burning. Data on global fuel production and the chemical composition of these fuels have been re-examined and an attempt has been made to estimate the fraction of fuel which is used in the petrochemicals industry or otherwise not soon oxidized. Available statistics now permit more systematic treatment of natural gas liquids than in earlier calculations. Values used for combustion efficiency and non-fuel use on a global scale still require some estimation and extrapolation from United States data but can be bounded with sufficient precision that they add little uncertainty to the calculation of global CO, emissions. Data now available permit the computation to be made with confidence that there are no major oversights. The differences from earlier calculations of CO, emissions are minor, well within the uncertainty limits in the data available. The fundamental problems of assembling a data set on global fuel production limit the utility of striving for too much precision at other steps in the calculation. Annual CO, emissions retain an uncertainty of 6-10%.Results of the calculations for 1980 through 1982 show decreases from 1979 CO, emissions. This is the first time since the end of World War I1 that the emissions have decreased 3 years in succession. During the period following the 1973 escalation of fuel prices, the growth rate of emissions has been less than half what it was during the 1950s and 1960s (1.5%/year since 1973 as opposed to 4.5%/year through the 1950s and 1960s). Most of the change is a result of decreased growth in the use of oil. through 1982, the amount of fossil fuel produced and the amount of CO, discharged to the atmosphere as a consequence. A final graph will display, for each fuel and for the global total, how CO, emissions have varied as a function of time. Tellus 36B (1984), 4 G. MARLAND A N D R. M. ROTTY 1 4 Imports 498 Domestic 932 G . MARLAND A N D R. M. ROTTY 382 Distillate Fuel Oil and Kerosene 172 Residual Fuel Oil 121 Jet Fuel 59 LPG and Ethane 85 Other (including adjustment) Refineries FO, = effective fraction oxidized in year of production = 0.9 18 -t 3 % C, = carbon content in tons C per ton crude oil = 0.85 ? 1 Yo CO,\ = CO, emissions in lo6 tons C P , = annual production in lo6 tons coal equivalent (? -1 1.2%) FO, = effective fraction oxidized in year of production = 0.982 & 2 % C, = carbon content in tons C per ton coal equivalent = 0.746** t 2% CO,, = CO, emissions in lo6 tons C P, = annual gas flaring in lo9 m' (? -20%) FO, = effective fraction oxidized in year of flaring = 1.00 ? 1 % C, = carbon content in tons per thousand m3 = 0.525 & 3 %

With growing concern about climatic changes that could result from increased atmospheric carbon dioxide, it is appropriate to use the improved statistics on the production and use of fossil fuels which are now available and to review the CO2 discharges to the atmosphere from fossil fuel burning. Data on global fuel production and the chemical composition of these fuels have been re‐examined and an attempt has been made to estimate the fraction of fuel which is used in the petrochemicals industry or otherwise not soon oxidized. Available statistics now permit more systematic treatment of natural gas liquids than in earlier calculations. Values used for combustion efficiency and non‐fuel use on a global scale still require some estimation and extrapolation from United States data but can be bounded with sufficient precision that they add little uncertainty to the calculation of global CO2 emissions. Data now available permit the computation to be made with confidence that there are no major oversights. The differences from earlier calculations of CO2 emissions are minor, well within the uncertainty limits in the data available. The fundamental problems of assembling a data set on global fuel production limit the utility of striving for too much precision at other steps in the calculation. Annual CO2 emissions retain an uncertainty of 6–10%. Results of the calculations for 1980 through 1982 show decreases from 1979 CO2 emissions. This is the first time since the end of World War II that the emissions have decreased 3 years in succession. During the period following the 1973 escalation of fuel prices, the growth rate of emissions has been less than half what it was during the 1950s and 1960s (1.5%/year since 1973 as opposed to 4.5%/year through the 1950s and 1960s). Most of the change is a result of decreased growth in the use of oil.

Seasonal vanat1ons are evident in the atmospheric C0 2 concentration, and attempts to understand the causes of the variations require an estimate of the seasonal pattern of the fossil fuel C0 2 source term. Estimates were made of C0 2 emissions resulting from fossil fuel combustion on a month-to-month basis for a recent typical year (1982). Twenty-one countries account for over 86% of the fossil fuel emissions. Monthly fuel consumption was used directly for those countries where such fuel data were available, and for the others (e.g., USSR and China) fuel use data were deduced from other factors. Results indicate that C0 2 emissions from gas fuel use show the largest seasonal variation, from 6.2% of the annual total in July or August to over I l.8% of the annual total in January. Liquid and solid fuel use shows less variation, with summer fractions about 7.8% of annual and winter about 9.2% of annual. Seasonal patterns are consistent throughout the Northern Hemisphere which dominates the global totals. Based on data for 87% of the world's fossil fuel C0 2 emissions, the highest release rate is 389.1 million tons of carbon in January and the lowest is 307.8 million tons of carbon in August. Statistics for Europe (especially vol. XXXI, no. 4). Economic Commission for Europe, United Nations.

Seasonal variations are evident in the atmospheric CO2 concentration, and attempts to understand the causes of the variations require an estimate of the seasonal pattern of the fossil fuel CO2 source term. Estimates were made of CO2 emissions resulting from fossil fuel combustion on a month‐to‐month basis for a recent typical year (1982). Twenty‐one countries account for over 86% of the fossil fuel emissions. Monthly fuel consumption was used directly for those countries where such fuel data were available, and for the others (e.g., USSR and China) fuel use data were deduced from other factors. Results indicate that CO2 emissions from gas fuel use show the largest seasonal variation, from 6.2% of the annual total in July or August to over 11.8% of the annual total in January. Liquid and solid fuel use shows less variation, with summer fractions about 7.8% of annual and winter about 9.2% of annual. Seasonal patterns are consistent throughout the Northern Hemisphere which dominates the global totals. Based on data for 87% of the world's fossil fuel CO2 emissions, the highest release rate is 389.1 million tons of carbon in January and the lowest is 307.8 million tons of carbon in August.

The atmospheric concentration of carbon dioxide is increasing. An important source of this excess carbon dioxide is the burning of fossil fuels for energy uses. This paper describes an estimate of the areal distribution of CO, emissions from energy sources. CO, from fuel burned in international bunkers is not included nor is CO, from gas flaring or cement manufacture. Emissions are calculated on a 5 O x 5' grid of latitude and longitude, based primarily on United Nations fuel use data. Fuel consumption data by country, by state within the US, and by province in Canada are used to calculate CO, emissions. Distribution of CO, emissions within these political entities is based on population distribution, using both discrete population data for subcountry units and population density maps. Aside from errors inherent in the U N fuel data and in our estimates for fuel composition and combustion efficiency, the major sources of error are (a) within-country regional variations in energy use per capita, (b) within-country regional variations in energy sources (e.g., hydroelectric versus coal electric), and (c) errors in our estimates of relative population density within political entities. While we believe regional patterns are accurately represented and that no CO, parcel is allocated very far from its correct source grid space, individual emission numbers by grid space are subject to large uncertainty. The final tabulation shows that 90% of total emissions are from the latitude band 20°-60° N, with the highest individual numbers from the grid spaces containing Frankfurt, London, and Tokyo.