CDIAC's popular Trends series continues to be produced as an online document accessible from CDIAC's Web site. It will no longer be produced in hard copy. Trends Online: A Compendium of Data on Global Change (http://cdiac.esd.ornl.gov/trends/trends.htm) provides synopses of frequently used time series of global-change data. Current contents of Trends Online include sections on:

• historical and modern records (from ice cores and current monitoring stations) of atmospheric concentrations of CO₂ (some records current through 1997);
• estimates of global, regional, and national CO₂ emissions from the combustion of fossil fuels, gas flaring, and the production of cement; and
• long-term records of atmospheric temperature.

The data summaries include tables; graphs; discussions of methods for collecting, measuring, and reporting the data; trends in the data; and references to literature providing further information.

In the future, Trends Online will include sections detailing information on global emissions estimates for CFC-11 and CFC-12, records of atmospheric methane concentrations, carbon content of the terrestrial biosphere, carbon fluxes to the atmosphere from land-use change, and long-term records of precipitation and cloudiness. In the meantime, links to CDIAC's already considerable holdings of such data (numeric data packages and online databases) are provided via the Trends Online Table of Contents.

The following presents a glimpse of two newly updated, important time series included in Trends Online.

Atmospheric CO₂ Concentrations--Mauna Loa Observatory, Hawaii, 1958-1996

(C. D. Keeling and T. P. Whorf) (http//cdiac.esd.ornl.gov/trends/co2/sio-mlo.htm)

The Mauna Loa atmospheric monthly CO₂ measurements from Keeling and Whorf constitute the longest continuous record of atmospheric CO₂ concentrations available in the world. The Mauna Loa site is considered one of the most favorable locations for measuring undisturbed air because possible local influences of vegetation or human activities on atmospheric CO₂ concentrations are minimal and any influences from volcanic vents may be excluded from the records. The methods and equipment used to obtain these measurements have remained essentially unchanged during the 39-year monitoring program.

Because of the favorable site location, continuous monitoring, and careful selection and scrutiny of the data, the Mauna Loa record is considered to be a precise record and a reliable indicator of the regional trend in the concentrations of atmospheric CO₂ in the middle layers of the troposphere. The Mauna Loa record shows a 14.8% increase in the mean annual atmospheric CO₂ concentration, from 315.83 parts per million by volume (ppmv) of dry air in 1959 to 362.57 ppmv in 1996.

Global and Hemispheric Temperature Anomalies--Land and Marine Instrumental Records, 1856-1997

(P. D. Jones et al.) (http://cdiac.esd.ornl.gov/trends/temp/jonescru/jones.html)

These temperature anomaly time series are derived from a global database of corrected land and marine temperature data.The land portion of the database is composed of surface air temperature data (land-surface meteorological data and fixed-position weather ship data) that have been corrected for nonclimatic errors, such as station shifts and/or instrument changes. The marine data consist of sea surface temperatures that incorporate in situ measurements from ships and buoys. These data have been used extensively in various Intergovernmental Panel on Climate Change (IPCC) reports.

The five warmest years of the global record have all occurred since 1990 and are, in descending order, 1997, 1995, 1990, 1991, and 1994. The record shows that the average surface air temperature of the globe has warmed ~0.5C since the middle of the nineteenth century.

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kng 05/98