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John C. Davis1, Geoffrey C. Bohling1
(1) Kansas Geological Survey, Lawrence, KS

Abstract: The search for patterns in ice core temperature curves

Predictions of global climate change are based on large computer-simulation models that are 'history-matched' to weather records compiled from the early 19th century onward. Climate change model forecasts would be more convincing if they were based on the natural records of the Holocene (i.e., 10,000 years) and were capable of emulating climate characteristics of this epoch. Temperature records estimated from oxygen isotope measurements on ice cores from the Greenland ice cap and the Antarctic could be used to develop models based on geochronological data rather than historically brief weather records.

The 20-year average record of oxygen isotope values from the Greenland GISP2 ice core exhibits a long-term trend of declining temperatures over most of the Holocene, except during the last 100 years when temperatures have increased-a change widely blamed on CO2 emissions from fossil fuels. However, the range in temperatures over the last 100 years is typical for the Holocene, and the current rate of increase in temperatures is not unusual. Past periods of consistently increasing (or decreasing) temperatures have not persisted much longer than the current interval, so temperature trends may well reverse in the near future. There are distinct cyclic patterns in temperatures recorded in the GISP2 ice core, including a pronounced saw-toothed, 560-year sequence of relatively abrupt change followed by a gradual reversal; the present trend may be the initial phase of such a pattern. In summary, the present climate does not appear significantly different than the past climate at times prior to industrialization.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana