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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999

FROM VOLUME 2, NUMBER 8, AUGUST 1989

PROFESSIONAL PUBLICATIONS...
TREND ANALYSIS

Item #d89aug29

"Steric Sea Level Trends in the Northeast Pacific Ocean: Possible Evidence of Global Sea Level Rise," R.E. Thomson (Inst. Ocean Sci., POB 6000, 9860 W. Saanich Rd., Sidney, B.C. V8L 4B2, Can.), S. Tabata, J. Clim., 2(6), 542 ff, 1989.

Thirty-year time series of hydrographic observations from Ocean Station PAPA and Line `P' are used to estimate secular trends in monthly mean steric sea level heights relative to depths of 100 and 1000 decibars in the northeast Pacific Ocean. Statistical analysis showed that steric sea levels in the northeast Pacific are rising at approximately 1 mm yr-1 and that this increase may be associated with a combined regional warming of the deeper waters and dilution of the surface waters. Although the observed trends appear to be linked to climate-induced eustatic changes in global sea level, the records are not of adequate length or spatial coverage to rule out effects of shifting regional circulation patterns.

Item #d89aug30

"Evidence for a Decline in the Atmospheric Accumulation Rate of CHClF2 (CFC-22)," C.P. Rinsland (Atmos. Sci. Div., NASA Langley Res. Ctr., Hampton VA 23665), D.W. Johnson et al., Nature, 337(6207), 535-539, Feb. 9, 1989.

Reports atmospheric CFC-22 measurements derived from ground-based solar spectra recorded between December 1980 and May 1988 which show that the CFC-22 total column increased at an average annual exponential rate of 7.8% + or - 1.0% (2 sigma). Compared with other atmospheric data, these measurements indicate that CFC-22 is increasing at a more rapid rate than either CFC-11 or CFC-12, the two most abundant chlorofluorocarbons, but that the rate of CFC-22 increase is likely to have declined over the past few years.

Item #d89aug31

"Reconstructed Northern Hemisphere Annual Temperature Since 1671 Based on High-Latitude Tree-Ring Data from North America," G.C. Jacoby Jr. (Tree-Ring Lab., Lamont-Doherty Geol. Obs., Palisades NY 10964), R. D'Arrigo, Clim. Change, 14(1), 39-59, 1989.

Reconstructions show a partial amelioration of the Little Ice Age after the early 1700's, an abrupt, severe renewal of cold in the early 1800's, and a prolonged warming since about 1840. These trends are supported by other proxy data. There appear to be relationships between trends observed in our Northern Hemisphere reconstruction and certain climatic forcing functions, including solar fluctuations, volcanic activity and atmospheric CO₂. Supports hypothesis that the global warming trend over the past century of increasing atmospheric CO₂ has exceeded the recent level of natural variability of the climate system.