Trends Online

CDIAC recently added a new section to Trends Online entitled "Methane Emissions" ( The initial data set in this section is annual estimates of global anthropogenic methane emissions for the period 1860-1994. The data were contributed by David Stern (Australian National University) and Robert Kaufmann (Boston University) and prepared for online publication by CDIAC's Bob Cushman. Methane is an important greenhouse gas, and a knowledge of anthropogenic emissions is important for studies of the biogeochemical cycling of methane and for consideration of strategies for reducing methane emissions.

CDIAC also added and revised several key records offered in the "Atmospheric Carbon Dioxide and Carbon Isotopes" section of Trends Online ( These new records were prepared by CDIAC's Mónica Martínez (summer student, University of Puerto Rico) and Tom Boden.

Ice-core CO2 records from Law Dome, Antarctica

These important ice core records were contributed by D. M. Etheridge, L. P. Steele, R. L. Langenfelds and R. J. Francey (CSIRO), J.-M. Barnola (Laboratoire de Glaciologie et Géophysique de l'Environnement), and V. I. Morgan (Antarctic CRC and Australian Antarctic Division). These data provide atmospheric CO2 mixing ratios from 1006 A.D. to 1978 A.D. The air enclosed in the three ice cores has unparalleled age resolution and extends into recent decades because of the high rate of snow accumulation at Law Dome. The Law Dome records show that preindustrial CO2 mixing ratios were in the range 275-284 parts per million, with the lower levels occurring from 1550 to 1800 A.D., probably as a result of colder global climate. The Law Dome ice core CO2 records show major growth in atmospheric CO2 levels over the industrial period, except during 1935-1945 A.D., when levels stabilized or decreased slightly. Such data have a number of important applications, such as studying the relationship between greenhouse gases and climate change and calibrating models of the global carbon cycle.

13CO2 record from Cape Grim, Tasmania

Roger Francey and Colin Allison (CSIRO) contributed this important isotopic carbon record to the Trends Online collection. The Cape Grim in situ record is possibly the most accurate representation of global atmospheric 13C behavior during the 1980s and 1990s. Changes in 13C of atmospheric CO2 are useful in elucidating the relative roles of oceanic and terrestrial uptake of CO2 from fossil fuel emissions.

Updates to the Scripps CO2 records

Dave Keeling and Tim Whorf (Scripps Institution of Oceanography) provided revisions and updates through 1997 to the monthly atmospheric CO2 records for Mauna Loa; Barrow, Alaska; American Samoa; and the South Pole. These records constitute some of the longest modern atmospheric CO2 records available.

Updates to German CO2 records

Revisions and updates through 1997 for the continuous atmospheric CO2 records from Schauinsland and Westerland were provided by Karin Uhse (Umweltbundesamt, Offenbach) and Martina Schmidt and Ingeborg Levin (University of Heidelberg). These records provide key long-term continental European records.

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