Publication Date:
2015-01-06
Description:
The reliability of an existing reconstructed annual (December–November) temperature series for the Lisbon region (Portugal) from 1600 onwards is assessed in the present study. The consistency of this series with: (1) five local borehole temperature-depth profiles; (2) synthetic temperature-depth profiles generated from both reconstructed temperatures and paleoclimate simulations in Portugal; (3) instrumental data sources over the twentieth century; and (4) temperature indices from documentary sources during the late Maunder Minimum (1675–1715) is assessed. It is found that reconstructed annual mean temperature series in Portugal, after European-wide reconstructions, is not consistent with both borehole profiles and paleoclimate simulations in their long-term variability and trends. Hence, the non-linear trend in the paleoclimate simulations is estimated and added to the reconstructed series (first-stage calibration). The annual reconstructed series is then calibrated in its location and scale parameters, using the instrumental series and a linear regression between them (second-stage calibration). The resulting calibrated series is then in clear accordance with the low-frequency variability of both borehole temperature-depth profiles and paleoclimate simulations. This calibrated series shows clear footprints of the Maunder and Dalton minima, mainly attributed to changes in solar activity and explosive volcanic eruptions, and a strong recent-past warming, attributed to human-driven forcing. Lastly, it is also in overall agreement with independently-derived annual temperature indices for the late Maunder Minimum. Thus, the series resulting of this re-calibration process for Lisbon can be of foremost relevance to improve the current understanding of the driving mechanisms of climate variability in Portugal.
Print ISSN:
1814-9340
Electronic ISSN:
1814-9359
Topics:
Geosciences
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