Comparison between proxies of solar magnetic activity and estimates of past terrestrial climate. The plotted time-period ranges from presence (right edge) back to 5000 years BC (left edge). The top curve (a) is a schematical plot of deviations of relative atmospheric C14 concentration normalized to the Maunder Minimum. Since the production rate of cosmogenic C14 isotopes is inversely related to solar activity, curve (a) is plotted upside down, i.e. downward excursions means increased relative C14 concentration (decreased solar activity). The second curve (b) represents a reconstruction of the solar activity cycle envelope based on curve (a). In section (c) four estimates of past climate are plotted. The shorter step-curve shows the advance and retreat of Alpine glaciers. The second step-curve (reaching back to 5000 BC) shows the same but for worldwide glacier fluctuations. The other two curves represents the mean annual temperature in England (dashed) and the winter-severity index for Paris-London areas (solid curve). The evident coincidence of periods of decreased averaged global temperature with low solar magnetic activity gives a strong hint towards a direct connection between solar irradiance variations and development of the Earth's climate, at least on the timescale under consideration. (from Eddy J.A., 1977, Climatic Change 1, 173)

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Last Update: 20 Feb. 1997