Wayne M. Wendland

Dating climatic episodes of the Holocene

Abstract Monitoring evidence indicates that the Holocene embraced a sequence of rather discrete climatic episodes. The transitions between these environmental episodes apparently were abrupt and globally synchronous. This paper reports on statistical analyses of radiocarbon dates associated with environmental change and cultural change. Over 800 14C dates associated with pollen maxima and minima, sea level maxima and minima, and top and bottom surfaces of peat beds were simultaneously analyzed to identify times of globally synchronous environmental discontinuities. Some 3700 14C dates associated with 155 cultural continua of the world were collectively analyzed to identify worldwide synchroneities in appearance and termination of the cultures. Significant globally synchronous discontinuities were identified in each independent analysis. The dates of environmental and cultural discontinuities are rather similar, particularly during the recent half of the Holocene. The fact that the cultural discontinuities mostly follow rather closely those of the paleobotanical record suggests that there has been a distinct climatic impact on the cultural history of man.

Northern Hemisphere Airstream Regions

Abstract Near-surface airstream source regions of the Northern Hemisphere have been identified using 16-year mean resultant winds from 3° latitude by 3° longitude grids. Tracing the airstreams back to their divergent centers reveals 19 different sources during various seasons of the year. Five of these sources(air originating over the North and South Pacific and Atlantic Oceans and air over Turkey) are resident in the Northern Hemisphere 12 months of the year. Another three (central Asian, Arctic and central East Asian air) exist for at least 11 months per year. The remaining 11 source regions are present from 1–9 months per year and their area of influence is much less than that of the 5 year-long sources. In the mean, there are several favored locations for frontal zones, e.g., a north–south band in Mexico (dividing Atlantic from Pacific air), a north–south band in northern South America, and two northeast–southwest trending bands over the cast coasts of Asia and North America, representing the mean lea...

Airstream Regions of North Africa and the Mediterranean

Abstract Mean monthly surface wind streamline charts for the North Africa-Mediterranean region are extracted from a previously prepared Northern Hemisphere set. These charts define mean airstream sources and mean confluences or “fronts.” Composite charts of airstream duration and seasonally stationary confluence positions are then extracted from the monthly streamline charts. The seasonality, duration and mean boundaries of the airstreams and their properties define a pattern of genetic climatic regions. This pattern derived entirely from climatic data is found to match the biotic pattern quite well.

Radiocarbon-calendar age relationship

Abstract Radiocarbon dated tree-rings from eight laboratories were analyzed by multiple regression and 250 yr means to determine the relationship between radiocarbon dates reduced to a common base and tree-ring (calendar) dates for the last 7100 yr. Both methods of analysis affirm the large scale differences reported elsewhere; however they do not substantiate the previously reported smaller scale fluctuations. Radiocarbon ages are younger than calendar ages from the present to ca. 500 yr ago and from 2100 to 7100 yr ago. From ca. 500 to 2100 yr ago, the two chronologies are nearly equal. The calendar-radiocarbon age relationships for individual laboratories are presented. Although small systematic differences are noted, their significance cannot be assessed at this time due to limited data.

Climatic Effects of Atmospheric Pollution

The trend of world temperature in this century appears to be directly related to the trends of atmospheric carbon dioxide content and atmospheric turbidity (dustiness). Both are believed by various scholars to be related to human activities. Since 1940, the effect of the rapid rise of atmospheric turbidity appears to have exceeded the effect of rising carbon dioxide, resulting in a rapid downward trend of temperature. There is no indication that these trends will be reversed, and there is some reason to believe that man-made pollution will have an increased effect in the future.

Atmospheric dustiness, man, and climatic change☆

Abstract During the past century the worlds mean temperature generally rose at least until the early 1940s, since when it has decreased. Three primary reasons for these trends have been hypothesized by various authors, namely, rising concentrations of atmospheric carbon dioxide brought about by the burning of fossil fuels, sunspot number variations, and dust injected into the atmosphere by volcanic eruptions. Although each of the above can explain short-term temperature trends, they cannot, singly, explain the entire record. The few observations of atmospheric dust concentrations that exist suggest that a catastrophic rise in concentration since the 1930s, due to human activities, may have overcome the warming trend prior to 1940 and caused the subsequent decrease in world mean temperature. The conservational implications of climatic change may be enormous —especially in terms of biogeography and biological productivity.

Southern Hemisphere Airstream Climatology

Abstract Estimates of mean monthly surface streamlines for the Southern Hemisphere were prepared from gridded mean surface geostrophic winds, from ship and land-based observations collected over several decades. The streamlines were arbitrarily drawn 20° clockwise to the geostrophic direction over oceans, 35° over relatively flat land, and 65° over rough terrain. Except over southern Africa, these assumptions were supported by a comparison between geostrophic directions and those of nearby mean vector winds. Four annual airstream sources were identified within the Southern Hemisphere: one each over the Indian, Pacific, and Atlantic Oceans, and a continental source over Antarctica. A fifth source region was identified over Australia during seven months centered on the Southern winter. Airstreams originating in the Northern Hemisphere penetrate into the Southern Hemisphere during summer, following the Intertropical Zone. During a mean year, 46% of the Southern Hemisphere experiences air originating from onl...

Phenological Crop–Climate Models for Illinois, 1951–80

Abstract To examine whether crop climate modeling using data based on phonological stages is appropriate for identifying different climatic effects on corn yields, two phonological models and a model using monthly data are devised for portions of Illinois for the period 1951–80. Comparisons of thew models show that there are no significant differences among the three models for the area as a whole. However, geographical differences in the suitability of these models are observed. When only a limited number of variables are used, the phenological models perform better for a major part of the state compared to the model based on calendar month data. Therefore, a fourth model called the Parsimonious Model, using selected variables from one of the two phenological models, is presented. The variables used in the Parsimonious Model represent the major agroclimatic controls on corn. Parsimonious models for sample areas show that climate has different impacts on corn yield variability in northern versus southern ...