Increasing evidence for significant solar forcing of temperatures and their disturbances over the 20th century

Abstract

The global temperature curves used in the 2007 IPCC report indicate significant warming beginning around 1975, considered to be anomalous and linked to anthropogenic release of greenhouse gases. There are some concerns however with geographical distribution of data and their uncertainties, particularly prior to 1900. We have given a new look to temperature data from Europe and the USA, using stations with long time series of daily values with almost no gap (150 in the USA, 44 in Europe). The trends of regional mean temperature curves vary significantly from one region to the other, and the overall mean curves are rather different from the IPCC report figures. Mean curves display linear segments separated by rather sudden slope change. In Europe, the trend is almost flat from 1900 to 1987, and since 1987 (contrary to what is often stated), and there is a sudden jump by ~1°C around 1987. We have estimated disturbances in temperature by evaluating the mean squared inter-annual variation of the data. The long-term changes in disturbances in mean temperatures in Europe, in the USA, also in Australia, are remarkably well correlated with the long-term evolution of most indices of solar activity over the 20th century. We will illustrate a number of other significant (actually often remarkable but previously not noticed) correlations between solar and climate parameters, that argue for a stronger role of the Sun on climate than is generally recognized.

Further information

• Courtillot-poster.pdf