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The search for causes of the rising temperatures in some geographic areas during the twentieth century has directed interest toward the amount of atmospheric carbon dioxide (GOa). If the carbon dioxide added by the combustion of fossil fuels remains as a net increase, any temperature-changing effects of its presence as a minor constituent of the atmosphere should be cumulatively operative as the amount increases. In this paper, the physical knowledge of atmospheric GO2 is examined and the available nineteenth and twentieth century observations of the atmospheric COa concentration are summarized to ascertain the extent t o which they corroborate claims that the amount of atmospheric COa has increased since the nineteenth century. In the light of the uncertainty of both physical knowledge and of statistical analysis, it is concluded that the question of a trend in atmospheric GO, concentration remains an open subject.

A number of diagrams are shown, contrasting day-by-day average temperatures at Washington with the accepted “normals”, showing extreme highest and lowest temperatures for each day of the year, the “January Thaw,” a recurrent cold period in February, an estimation of the potentially highest and lowest temperatures at Washington, and recent abnormal temperature trends are discussed. The annual day-by-day march of degree days for heating is also noted. The results in general suggest some revision of the popular conception of “normals” is in order.

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