© 2000,

AAPG/DEG

, 1075-9565/00/$15.00/0Environmental Geosciences, Volume 7, Number 4, December 2000 213–216

A A P G A N N U A L M E E T I N G A B S T R A C T S

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American Association of Petroleum Geologists Annual Meeting Abstracts,April 16–19, 2000, New Orleans, LA

GLOBAL CLIMATE CHANGE AND CONSEQUENCES

A Climate of Doubt about Global Warming

Dr. Robert C. Balling, Jr., Office of Climatology, Arizona State University, Tempe, AZ 85287-1508

According to numerical models of climate, the continuedbuildup of greenhouse gases will lead to a substantial rise inplanetary temperature and many related changes to the cli-mate system. Empiricists have noted that thermometer-based planetary temperatures have increased over the pastcentury, thereby providing support for the theoretical pre-dictions of the models. Many nations have called for actionto combat the threat of global warming, and the Kyoto Pro-tocol represents a major first step in the policy arena.

However, many of the most fundamental global warmingissues remain in a state of considerable debate in the scien-tific community. For example, in the most recent half de-cade, the atmospheric concentration of many greenhousegases has slowed or even stabilized. The numerical modelsof the climate continue to have serious weaknesses includ-ing their representation of cloud processes and the couplingof the atmosphere and ocean. Thermometer records mayshow warming, but serious concerns remain about the truerepresentativeness of their readings. In addition, increasedoutput of the sun, lack of recent volcanism, and trends in ElNiño/Southern Oscillation have certainly contributed to anyobserved warming. The entire issue is further complicatedby the fact that satellite-based and balloon-based measure-ments of lower atmospheric temperatures show no warmingwhatsoever over the past few decades. Also, there appearsto be no increase in tropical cyclone activity, severe weatherevents, or variability of climate. Finally, the evidence is over-whelming that the climate impact of a fully implemented Ky-oto Protocol will be trivial over the next 50 years.

The Magnitude and Rate of Past Global Climate Changes

John P. Bluemle, North Dakota Geological Survey, Bismarck, ND; Joseph M. Sabel, U.S.

Coast Guard Civil Engineering Unit, Oakland, CA; and Wibjörn Karlén, Department of Physical Geography, Stockholm University, Sweden

The earth’s climate is constantly changing and currentlywarming. This paper is an evaluation of previous climatechanges intended to test the validity of assigning causalityto human activity. Records of glacial advances and retreatsindicate changes in relative summer temperature. Lacustrineand subaerial sediments afford a record of glacier advancesand retreats from the end of the Pleistocene. Palynology of-fers a record of species succession in response to climatechanges. Dendrochronology indicates summer temperature.Isotope paleontology provides a measurement of tempera-ture at the time of marine sediment deposition. Isotopicevaluation of continental ice is an indicator of temperatureat the time of precipitation. Anthropologic sources providesignificant climate data, such as information about villagesoverrun by glaciers, open-ocean iceberg density, or harborsfilled with ice. Available sources record continual changesin climate. The temperature lowered 15 to 20

8

C from thePaleocene to the Neogene. Another 10

8

C change occurredin the Pleistocene. Correlative data from North America,Greenland, and Scandinavia indicate many climate changeswere global in scope. It is difficult to develop precise paleo-thermometry, but qualitative evaluations indicate suddenand dramatic changes in climate.

Some changes are perhaps as great as a change from con-ditions warmer than today, to a full glacial climate in as lit-tle as 100 years. The converse can be true. Current data in-dicate a trend of change that is severe but no greater in rateor magnitude, and probably less in both, than many changesthat have occurred in the recent geologic past.

The Search for Patterns in Ice Core Temperature Curves

John C. Davis and Geoffrey C. Bohling, Kansas Geological Survey, 1930 Constant Ave., Lawrence, KS 66047

Predictions of global climate change are based on largecomputer-simulation models that are “history-matched” to

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weather records compiled from the early 19th century on-ward. Climate change model forecasts would be more con-vincing if they were based on the natural records of the Ho-locene (i.e., 10,000 years) and were capable of emulatingclimate characteristics of this epoch. Temperature recordsestimated from oxygen isotope measurements on ice coresfrom the Greenland ice cap and the Antarctic could be usedto develop models based on geochronological data ratherthan historically brief weather records.

The 20-year average record of oxygen isotope valuesfrom the Greenland GISP2 ice core exhibits a long-termtrend of declining temperatures over most of the Holocene,except during the last 100 years when temperatures have in-creased, a change widely blamed on CO

2

emissions fromfossil fuels. However, the range in temperatures over thelast 100 years is typical for the Holocene, and the currentrate of increase in temperatures is not unusual. Past periodsof consistently increasing (or decreasing) temperatures havenot persisted much longer than the current interval, so tem-perature trends may well reverse in the near future. Thereare distinct cyclic patterns in temperatures recorded in theGISP2 ice core, including a pronounced saw-toothed, 560-year sequence of relatively abrupt change followed by agradual reversal; the present trend may be the initial phaseof such a pattern. In summary, the present climate does notappear significantly different than the past climate at timesprior to industrialization.

Sea Level Changes in the Baltic Sea–Interrelation of Climatic and Geologic Processes

Jan Harff, Marine Geology Section, Baltic Sea Research Institute, Warnemünde, D-18119, Germany; Alexander Frischbutter, Geologic Institute, Potsdam, Germany; Reinhard Lampe, Geographical Institute, University of Greifswald, Germany; and Michael Meyer, Institute of Geological Sciences, University of Greifswald, Germany

The development of the Baltic Sea is largely dominatedby climatically controlled eustatic sea level changes andvertical crustal movement during the Holocene. Both fac-tors are overlain in the records of relative sea level changeand differ remarkably around the Baltic Sea. The compari-son of relative sea level curves with a eustatic curve revealsthe contribution of vertical crustal movement to the coastalchange process. A coast index c(i) is derived by which a lo-cation can be allocated to a “crustal uplift/subsidence type”or a “climate-controlled type.” Coastal locations investigatedat the Fennoscandian Shield belong to the crustal-uplifttype, and locations at the southern and southwestern coastbelong to the climate-controlled type independently of theirposition at the East-European or the West-European Plat-

form. Data for recent vertical crustal movements show a broadpredominantly subsiding zone between the rising blocks ofScandinavia (glacio-isostatic uplift) and the Carpathians(N-drift of the Africa Plate), which is to the west of theTornquist-Teisseyre Zone additionally influenced by pro-cesses initiated by North Atlantic Ridge movements. Theanalysis of relative sea level changes leads to the assump-tion that the subsidence of a belt contiguous to the Fenno-scandian Shield, interpreted as a collapsing asthenosphericbulge in front of former Pleistocene glaciers, reached a steadystate during the Late Litorina Stage. Crustal movement datatogether with data from modeling of future sea level changecan be used for the sustainable development of coastal areas.

Climate Change—Impacts and Efforts

David A. Jenkins, East Road, Weybridge, Surrey KT13 OLB, United Kingdom

An awareness and understanding of the palaeoclimatolog-ical history of the planet allows a different construct for to-day’s concerns about the impacts of future climatic changes.

In particular, a better appreciation of the magnitude andrate of change during the past few hundred thousand yearsdemonstrates that the changes anticipated during the nextfew hundred are well within the range experienced duringthe Pleistocene Era.

The planet is now in a period of gradual cooling from thetime of the post-glacial thermal optimum 6000–9000 yearsago. Temperatures are now on an irregular downward path,comparable to the Eemian interglacial, although at present weare experiencing a minor temperature increase as a partial re-covery from the “Little Ice Age,” which ended 150 years ago.

Climate will always change. The planet is extremely resil-ient. As the most intelligent species that has colonized thesurface, humans clearly have ample capability to adapt.However, our ability to do so will be limited by our politicaland behavioral patterns.

The well-documented evidence from the climate changesin the northern hemisphere during the past 1000 years indi-cates that changes in average global temperatures of 2

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Cwill have significant regional impacts on precipitation andvegetation patterns and lead to further changes in sea level.From the viewpoint of the demands of an increasing globalpopulation, these could be managed, given appropriate lev-els of investment. Warming is definitely easier to cope withthan is cooling. Stability is not an option.

Carbon Cycle in the Past 300 Years and Future Projections

F. T. Mackenzie, Department of Oceanography, SOEST, University of Hawaii, Honolulu, HI 96822, A. Lerman, Department of Geological Sciences, Northwestern University, Evanston, IL 60208, and L. M. B. Ver, Department of

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Oceanography, SOEST, University of Hawaii, Honolulu, HI 96822

Four major perturbations owing to human activities onland and global temperature change have affected the globalcarbon cycle since the year 1700. The process-driven modelof the coupled biogeochemical cycles of C-N-P-S (TOTEM)analyzes the cycles of these elements as forced by globalemissions from fossil-fuel burning, land-use change, agricul-tural fertilization of croplands, organic sewage discharges,and a slight temperature rise. The model results for atmo-spheric CO

2

change in the past 300 years agree well withthe observed increase. The model estimates the increases inthe delivery of land-derived carbon and its transformationsin the coastal ocean, changes in the trophic status (net heterotro-phy or autotrophy) of the coastal ocean, and consequences ofpossible changes in the oceanic thermohaline circulation. Themodel also estimates the atmospheric concentration and stor-age and transport of carbon for future decades to the middleof the 21st century, based on different scenarios of environ-mental perturbations.

Solar Forcing of Earth’s Climate

Alfred H. Pekarek, Department of Earth Sciences, St. Cloud State University, St. Cloud, MN 56301

The sun is the primary source of energy for the climate ofthe earth. Variations in solar energy reaching the earth’ssurface change the climate. Several factors control the in-flux of solar energy including (1) variations in the earth’salbedo, (2) variations in earth’s orbit and rotation, and (3)variations in solar energy output.

In the short time since 1978, direct measurement of totalsolar irradiance (TSI) by satellites has shown cyclical varia-tions in solar energy of 0.1% in conjunction with the 11-year sunspot cycle. Indirect evidence from the Sun andother sun-like stars indicates that TSI has had significantlygreater variation as the Sun goes through various cycles.

The correlations between climate and TSI variations arestatistically solid. Small variations in TSI initiate indirectmechanisms on earth that yield climate changes greater thanthat predicted for the TSI change alone. At least three solarvariables are known to affect earth’s climate: (1) TSI, whichdirectly affects temperatures; (2) solar ultraviolet radiation,which affects ozone production and upper atmosphericwinds; and (3) the solar wind, which affects rainfall andcloud cover at least partially through control of earth’s elec-trical field. Each affects the earth’s climate in differentways, producing indirect effects that amplify small changesin TSI. Individually, they do not cause the entire observedclimatic changes. Collectively, they appear sufficient espe-cially since solar forcing of earth’s climate is still an emerg-ing science. Undoubtedly, other mechanisms of solar forc-ing are poorly understood, perhaps even unknown.

Microbial Calcification: Implicationsfor Marine Whitings and Inorganic Carbon Cycling

Lisa L. Robbins and Kimberly K. Yates, Center for Coastal and Marine Geology, U.S. Geological Survey, 600 Forth Street South, St. Petersburg, FL 33701

Microbial calcification has been identified as a significantsource of carbonate sediment production in modern marineand lacustrine environments around the globe. This processhas been linked to the production of modern whitings andlarge, micritic carbonate deposits throughout the geologicalrecord. Recent research has advanced our understanding ofthe microbial calcification mechanism as a photosyntheti-cally driven process. However, little is known of the effectsof this process on inorganic carbon cycling or of the effectsof changing atmospheric CO

2

concentrations on microbialcalcification mechanisms.

Coral Reefs and Shoreline Sedimentation: Bathtub Rings around the Sea

Gene Shinn, Center for Coastal Geology, U.S. Geological Survey, St. Petersburg, FL 33701

Deep sea and ice cores show that sea level and thus globaltemperature fluctuated often during the past 1.8 millionyears. Fossil coral reefs, tidal flats, and beaches are preciseindicators of former sea level. Although large fluctuationsare indicated by the geologic record, this paper focuses onthe younger well-documented fluctuations recorded bycoral reefs and shoreline deposits that accumulated duringthe past 140,000 years. During this relatively short period,fossil coral species and depositional processes have re-mained unchanged and diagenetic alteration of fossils andsediments was minimal. Coral reefs and shoreline accumu-lations were selected as sea-level indicators for two reasons:(1) they serve as bathtub rings and/or dipsticks for deter-mining former sea levels, and (2) human activity had no in-fluence on the sea in which they grew or accumulated.

Emergent coral reefs worldwide suggest that global sealevel was at least 6 m above present during isotope stage 5e

z

120 ka. Drowned coral reefs and oolitic beaches indicatesea level was

z

100 m below present during stage 2 as littleas 12 ka. As many as eight sea-level fluctuations occurredbetween stages 2 and 5e, each of which was greater thanthose projected to result from burning fossil fuels. Ice coredata suggest even more fluctuations between stages 5a and5e. Because the record is written in stone, geologists, espe-cially sedimentologists, should be well qualified to make fu-ture predictions. Geologists have for the most part been ex-cluded from official decision making.

Direct measurements of air:sea CO

2

gas fluxes and car-bonate sediment production rates were measured in whit-

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ings located on the Great Bahama Bank and in laboratorycultures of calcifying cyanobacteria and unicellular greenalgae. In situ gas flux measurements showed a reduction inatmospheric CO

2

relative to adjacent waters outside of whit-ings. Similar results were also observed in laboratory cul-tures. Calcification rates in whitings and laboratory culturesranged from

z

0.06 to 34.5 g CaCO

3

m

2

3

hr

2

1

. These resultssuggest that production of microbial carbonates may serveas a sink for inorganic carbon. Laboratory cultures of calci-fying microbes were subjected to biological buffers to ex-amine the role of photosynthetic uptake of inorganic carbonspecies in calcification. Results from these experiments in-dicate that microbial calcification mechanisms depend uponthe species of inorganic carbon available to cells for photo-synthesis and, thus, atmospheric CO

2

concentrations. Theseresults suggest fluctuations in Phanerozoic dominance trendsfor calcareous cyanobacteria and algae may be linked tofluctuations in atmospheric CO

2

.

Henry’s Law and Its Oceanographic Implications

Douglas B. Swift, West Texas Earth Resources Institute, Midland, TX 79705

The hydrosphere is the Earth’s single greatest reservoir(35,000 billion metric tons [BMT]) of mobile carbon frac-tion CO

2

(cfCO

2

). The atmosphere holds

z

740–760 BMT.Henry’s Law (HL) defines the proportional relationship be-

tween a soluble gas (e.g., CO

2

) and a liquid (water) across agas/liquid interface (atmosphere/hydrosphere boundary). Thelaw is temperature dependent; cool liquid absorbs more gasthan does warm liquid. Throughout the geologic record,large volumes of CO

2

have been immobilized through HL-driven carbonate deposition.

Application of HL explains several anomalies in the re-cent atmospheric record, including (1) the “missing” CO

2

ofthe carbon budget. Anthropogenic sources generate

z

6–7BMT of cfCO

2

, annually. Atmospheric cfCO

2

has onlygrown at a rate of

z

3.8 BMT annually. (2) Analysis of icecore data clearly demonstrates concentration of atmosphericCO

2

trapped in ice, following temperature changes, ratherthan driving them. (3) Global temperature drop (1992–1993) following the eruption of Pinatuba is associated withan anomalous decelleration in the growth of atmosphericgreenhouse gases.

Presently, climate models do not directly incorporate HLand its derivative effects on heterogeneous circulating oce-anic water masses, with their substantial temperature ranges.In a solar-forced warming scenario, increased oceanic tem-peratures must drive an increase in atmospheric CO

2

. Bothanthropogenic and HL additions to atmospheric CO

2

con-tent must be taken into consideration. Application of HL ex-plains anomalies, while raising questions concerning possi-ble disadvantages of natural and/or anthropogenic oceanicsequestration of CO

2

. It also raises questions concerningpresent applied thermal forcing values for atmospheric CO

2

.