EARTHTRENDS DATA TABLES TECHNICAL NOTES: Global Climate Trends 2005 For more information, please consult http://earthtrends.wri.org VARIABLE DEFINITIONS AND METHODOLOGY Mean Global Surface Temperature The NASA Goddard Institute for Space Studies (GISS) Surface Temperature Analysis (GISTEMP) estimates mean global temperatures by dividing the world into broad latitude zones, estimating time series data for each zone, and then weighting these zones by their area. The zones are northern latitudes (90°N-23.6°N), low latitudes (23.6°N-23.6°S), and southern latitudes (23.6°S-90°S), and respectively cover 30%, 40% and 30% of the Earth’s surface. The annual values shown here are averages calculated by WRI of monthly values calculated by GISTEMP. All 5-year means refer to the five year period ending in the observation year. Atmospheric Concentration of Carbon Dioxide (CO2) is the average mole fraction of CO2 in water-vapor-free air. Concentrations are measured in parts per million by volume (ppmv). Data from 1744-1959 are estimated by measuring CO2 concentrations of air enclosed in an ice core at Siple Station, Antarctica. The age of the air trapped in the sample is estimated based on the depth of the core measurement and the age of the surrounding ice. Post-1959 data presented here are from the Scripps Institution of Oceanography observatory in Mauna Loa, Hawaii (19 degrees 32 minutes North latitude, 155 degrees 35 minutes West longitude). The Mauna Loa dataset is the longest continuous record of atmospheric CO2 concentrations in the world. In years where one monthly value is missing, annual values were calculated by substituting a fit value (4-harmonics with gain factor and spline) for that month and then averaging the twelve monthly values. Details concerning data collection, revisions, and analysis are contained in C.D. Keeling, et al., Measurement of the Concentration of Carbon Dioxide at Mauna Loa Observatory, Hawaii, in W.C. Clark, ed., Carbon Dioxide Review: 1982 (Oxford University Press, New York, 1982). Atmospheric Concentration of Non-CO2 Greenhouse and Ozone-Depleting Gases refer to those gases which destroy atmospheric ozone, contribute to the greenhouse effect, or both. Data are given in terms of the annual average dry air mole fraction, measured in parts per billion (ppb) for methane and nitrous oxide and parts per trillion (ppt) for carbon tetrachloride, methyl chloroform, and CFCs. * Methane (CH4) acts to increase ozone in the troposphere and lower stratosphere. On a molecule-for-molecule basis, methane is 21 times more powerful than CO2 at trapping heat in the atmosphere. Anthropogenic methane emission sources include waste management (landfills), livestock management (enteric fermentation in ruminants), anaerobic respiration in the soils associated with wet rice agriculture, and combustion of fossil fuels and biomass (wood fuel and cleared forests). Sources of non-anthropogenic emissions include anaerobic respiration in the soils of moist forests, wetlands, bogs, tundra, and lakes. * Nitrous oxide (N2O) is an important depletor of stratospheric ozone and is 310 times more powerful than CO2 at trapping heat in the atmosphere. N2O is emitted by anthropogenic activities such as combustion of fossil fuels and biomass (wood fuel and cleared forests) and the use of nitrogenous fertilizers. Non-anthropogenic sources include aerobic decomposition of organic matter in oceans and soils by bacteria, and through other processes. * Carbon Tetrachloride (CCl4) is an intermediate product resulting from the production of CFC-11 and CFC-12. It is also used in other chemical and pharmaceutical applications and for grain fumigation. Compared with other gases, carbon tetrachloride makes a small contribution to the greenhouse effect and to stratospheric ozone depletion. * Methyl Chloroform (CH3CCl3) is used primarily as an industrial degreasing agent and as a solvent for paints and adhesives. Its contribution to the greenhouse effect and to stratospheric ozone depletion is relatively small. * CFC-11 (CCl3F), CFC-12 (CCl2F2), and CFC-113 (C2Cl3F3) are potent depletors of stratospheric ozone. In addition, their cumulative effect on global warming may equal one-fourth that of CO2. CFCs are used as solvents and in many applications including refrigeration, air conditioning, foam blowing, and cleaning of electronics components. FREQUENCY OF UPDATE BY DATA PROVIDERS Mean Global Surface Temperature GISTEMP data are updated monthly. The data is limited to the period since 1880 because of the poor spatial coverage of stations prior to that time and the reduced possibility of checking records against those of nearby neighbors. Atmospheric Concentration of Carbon Dioxide Historical (pre-industrial) carbon dioxide estimates begin in 1744 and are available for 22 different years between 1744 and 1953. The data were initially published in 1986. Data from the Mauna Loa observatory have been reported from 1958 to 2003. While EarthTrends reports annual averages, the Mauna Loa data are recorded monthly, except for a few interruptions. CDIAC updates the Mauna Loa dataset on their website at least once a year; data for 2003 were posted on CDIAC’s website in June, 2004. Atmospheric Concentration of Non-CO2 Greenhouse and Ozone-Depleting Gases Non-CO2 data are from the monitoring station at Cape Grim, Tasmania (45 degrees 41 minutes South latitude, 144 degrees 41 minutes East longitude) under the ALE/GAGE/AGAGE program. The program is divided into three parts based on three different types of instrumentation using different calibration gases. The data reported here from 1978-81 are from the Atmospheric Lifetime Experiment Program (ALE); 1982-93 data are from the Global Atmospheric Gases Experiment (GAGE); 1994-2004 data are from the Advanced GAGE (AGAGE). Cape Grim generally receives unpolluted air from the Southeast and is the station with the longest, most complete dataset. Air samples were collected 4 times daily for ALE, 12 times daily for GAGE, and 30 times daily at each site for AGAGE. The annual values shown here are averages calculated by WRI of monthly values calculated by CDIAC. Missing values were interpolated. The SIO-1998 calibration scale was applied to the entire data set to create a unified record of gas concentrations. The calibration method is described in detail in Prinn et al., 2000, A History of Chemically and Radiatively Important Gases in Air Deduced from ALE/GAGE/AGAGE. Journal of Geophysical Research, 115: 17751-92. DATA RELIABILITY AND CAUTIONARY NOTES Mean Global Surface Temperature Mean temperature data is calculated based on the global mean temperature estimated for 1951-1980, 14° Celsius. Although the true value may differ by as much as a half a degree Celsius, any such difference will only affect point values within the dataset, not the trend of temperature change over time. Data errors are expected to be minimal. GISTEMP’s global maps of temperature change illustrate that the analyzed temperature changes generally have a clear physical basis associated with large-scale climatological patterns, and the greatest changes occur in remote locations where effects of local human influence are minimal. Atmospheric Concentration of Carbon Dioxide The carbon dioxide measurements presented here reflect global trends. However, it is important to note that CO2 concentrations differ significantly among monitoring sites at any given time. The data presented here in EarthTrends are specific to the locations where the measurements were taken and are not global averages. For example, the average annual concentration at the South Pole in 1997 was 2.3 parts per million lower than at Mauna Loa. Annual means disguise large daily and seasonal variations in CO2 concentrations. During the summer, photosynthetic plants store larger amounts of carbon than in the winter, resulting in seasonal variation in measurements. The data from the Mauna Loa station reflect very precise measurements. Data are revised to correct for drift in instrument calibration, hardware changes, and perturbations to "background" conditions. Early in the data series, some CO2 measurements are missing for up to 3 consecutive months; for these series, annual mean figures were derived using interpolated data. The measurements of pre-industrial CO2 concentrations are estimates and not as reliable as current measurements from Mauna Loa. However, numerous groups have arrived at very similar CO2 concentration measurements using air trapped in ice cores taken from the Siple Station. In addition, the data agree with measurements of CO2 in ice cores taken at other sites, such as the Law Dome Ice Core, also in Antarctica. Atmospheric Concentration of Non-CO2 Greenhouse and Ozone-Depleting Gases The data from the ALE/GAGE/AGAGE system reflect very precise measurements. Data are revised to correct for drift in instrument calibration, hardware changes, and perturbations to "background" conditions. Early in the data series, some measurements are missing for several months; for these series, annual mean figures were derived using interpolated data. The non-CO2 greenhouse and ozone-depleting gas measurements presented here reflect global trends. However, it is important to note that nitrous oxide concentrations differ significantly among monitoring sites at any given time. The data presented here are specific to the locations where the measurements were taken and are not global averages. For a more complete record of the monthly data showing the number of measurements taken and the standard deviation of each set of measurements, please consult the following web pages: ALE data: http://cdiac.ornl.gov/ftp/ale_gage_Agage/ALE/monthly/tamon.sum GAGE data: http://cdiac.ornl.gov/ftp/ale_gage_Agage/GAGE/monthly/tgmon.sum AGAGE Data: http://cdiac.ornl.gov/ftp/ale_gage_Agage/AGAGE/gc-md/monthly/tAmon.sum SOURCES Mean Global Surface Temperature NASA GISS Surface Temperature Analysis (GISTEMP). 2005. Table of Global-Mean Monthly, Annual and Seasonal Land-Ocean Temperature Index. New York: Goddard Institute for Space Studies. Available online at http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts+dSST.txt. Atmospheric Concentration of Carbon Dioxide Data before 1958: Neftel, Friedli, Moore, et al. 1994. Historical Carbon Dioxide Record from the Siple Station Ice Core. Reported on-line by the Carbon Dioxide Information Analysis Center (CDIAC) at http://cdiac.esd.ornl.gov/trends/co2/siple.htm. Bern, Switzerland: University of Bern. Data after 1958: Keeling, C.D., Whorf, T.P., and the Scripps Institute of Oceanography. 2004. Atmospheric CO2 Concentrations (ppmv) Derived from In-Situ Air Samples Collected at Mauna Loa Observatory, Hawaii. Reported on-line by the Carbon Dioxide Information Analysis Center (CDIAC) at http://cdiac.esd.ornl.gov/trends/co2/sio-mlo.htm. Mauna Loa: Scripps Institute of Oceanography. Atmospheric Concentration of Non-CO2 Greenhouse and Ozone-Depleting Gases Prinn, R.G., R.F. Weiss, P.J. Fraser, P.G. Simmonds, D.M. Cunnold, F.N. Alyea, S. O'Doherty, P. Salameh, B.R. Miller, J. Huang, R.H.J. Wang, D.E. Hartley, C. Harth, L.P. Steele, G. Sturrock, P.M. Midgely, and A. McCulloch. 2000. A History of Chemically and Radiatively Important Gases in Air Deduced from ALE/GAGE/AGAGE, Journal of Geophysical Research, 115, 17751-17792. Available online at http://cdiac.ornl.gov/ftp/ale_gage_Agage/. Data from the ALE/GAGE/AGAGE project were originally reported in: * Methane (CH4) Cunnold, D.M., Steele, L.P., Fraser, P.J., Simmonds, P.G., Prinn, R.G., Weiss, R.F., Porter, L.W., Langenfelds, R.L., Wang, H.J., Emmons, L., Tie, X.X., and Dlugokencky, E.J. 2002. In situ measurements of atmospheric methane at GAGE/AGAGE sites during 1985-2000 and resulting source inferences. Journal of Geophysical Research, 107, D14, doi: 10.1029/2001JD001226. * Nitrous Oxide (N2O) Prinn, R.G., Cunnold, D., Rasmussen, R., Simmonds, P., Alyea, F., Crawford, A., Fraser, P., and Rosen, R. 1990. Atmospheric emissions and trends of nitrous oxide deduced from ten years of ALE/GAGE data. Journal of Geophysical Research, 95, 18369-18385. * Carbon Tetrachloride (CCl4) Simmonds, P.G., Cunnold, D.M., Weiss, R.F., Prinn, R.G., Fraser, P.J., McCulloch, A., Alyea, F.N., and O'Doherty, S. 1998. Global trends and emission estimates of CCl4 from in situ background observations from July 1978 to June 1996. Journal of Geophysical Research, 103 (D13), 16017-16027. * Methyl Chloroform (CH3CCl3) O'Dorherty, S., Simmonds, P., Cunnold, D., Wang, R.H.J., Sturrock, G.A., Fraser, P.J., Ryall, D., Weiss, R. F., Salameh, P., Miller, B.R., and Prinn, R.G. 2001. In situ Chloroform Measurements at AGAGE Atmospheric Research Stations from 1994-1998, Journal of Geophysical Research, 106, 20429-20444. * Chlorofluorocarbons (CFC-11, CFC-12, and CFC-13). Cunnold, D., Weiss, R., Prinn, R., Hartley, D., Simmonds, P., Fraser, P., Miller, B., Alyea, F., and Porter. L. 1997. GAGE/AGAGE measurements indicating reductions in global emissions of CCl3F and CCl2F2 in 1992-1994. Journal of Geophysical Research, 102, 1259-1269. Fraser, P., Cunnold, D., Alyea, F., Weiss, R., Prinn, R., Simmonds, P., and Miller, B. 1996. Lifetime and Emission Estimates of 1,1,2-Trichlorotrifluorethane (CFC-113) from Daily Global Background Observations, June 1982-June 1994. Journal of Geophysical Research, 101, 12585-12599.