How Real is the Greenhouse Effect?

A focus of recent concern is the effect of the increasing quantities of carbon dioxide and other so-called 'greenhouse gases' on the earth's climate. Numerous attempts have been made to detect the predicted climatic changes but, because the available records are very short, standard time-series methods perform poorly and the results remain controversial. To improve statistical efficiency, we apply a multiple window approach to estimate the trends and power spectra of both the Hansen-Lebedeff average global surface temperature series and Keeling's CO sub 2 concentration measurements and the coherence between the two series.