Long-term climate change and surface versus underground temperature measurements in Paris

摘要

Careful temperature measurements performed from 1783 to 1852 in underground galleries, 28 m below the Paris Observatory, are compared with current measurements performed in a limestone quarry, 20 m below ground surface, and with local and European surface temperature records. When averaged using a backward 11-year moving window, the surface temperature time series looks similar and exhibits the already well-known 1 degrees C temperature increase over the last century. In addition, since about 1987, a steeper increase of about 0.07 degrees C per year is noticed on all surface records. Underground temperatures, unaffected by surface fluctuations and averaging procedures, show a 0.9 degrees C increase and thus confirm the trend indicated by the surface records. The averaged time series of the temperature in Paris and of the Wolf number, an indicator of sunspot activity, were reasonably well correlated till 1987 but deviated significantly from each other after that date. The long-term connection between surface temperature and solar cycles is further supported by a temporal analysis of the frequency content at 11 years and 5.5 years. Visual correlations between temperature and sunspot numbers, unconvincing when using recent records, appear more striking with underground data from 1783 to 1852. This analysis suggests that solar activity played an important role in temperature changes till the last century, but that different processes, possibly related to human-induced changes in the climate system, have been taking place lately with increasing intensity, especially since 1987. Copyright (c) 2005 Royal Meteorological Society.