Quality data development and noticeable thermal changes om Spain

El objetivo de este trabajo es ofrecer una metodología para el desarrollo de bases de datos de largo recorrido de temperatura diaria ajustada, reflexionando sobre la dificultad en recabar datos climáticos históricos e información sobre ellos, las causas más habituales de sesgo en las series de temperatura diaria españolas, las metodologías empleadas con éxito en la detección de errores y rupturas de homogeneidad de las series y las herramientas desarrolladas por los autores para su minimización. A partir de los datos ajustados se construyen series regionales de temperatura y se detallan las significativas tendencias al calentamiento detectadas en la temperatura media, máxima y mínima diaria española, intensificadas en las últimas décadas.The goal of this paper is to offer a methodology for the development of long-term daily adjusted temperature datasets. We discuss about the problems related with the compilation of historical climate data, the most common biases impacting the series of daily temperatures in Spain and the successful methods applied to the detection of inhomogeneities and the tools developed for the minimization of their effect over the time series. After this, we construct regional series from the adjusted data and study and detail the significant trends found in mean, maximum and minimum daily temperature series for the last decades in Spain

Estimated autumn precipitation anomalies in the Central Pyrenees between 1500 and 2002 CE, based on the varved sediments of Lake Montcortès

The Mediterranean region is expected to be highly impacted by global warming. To better understand and predict shifts in its current climate system, climate time series covering seasonal-to-century scale climate variability are needed. Here we provide a dataset containing a high-resolution reconstruction of autumn precipitation variability for the Central Pyrenees that spans the 1500-2002 CE period. This dataset is based on calcite sublayer width of varved sediments of lake Montcortès. Sediment cores MON12-3A-1G and MON12-2A-1G were retrieved from the deepest basin of the lake. Large-scale thin sections of sediment (120 mm X 35 mm) were extracted and calcite varve sublaminae counted and characterised. The age-depth model was built by combining varve counting and radiometric dating (210Pb, 137Cs and 14C). Long-term trend of the raw calcite width series was removed with a low pass filter by fitting a cubic smoothing spline of 67% of the series length. To find out how well the smoothed calcite series and instrumental regional precipitation match up with each other, correlation and cross correlation methods were applied. Highest correlation values were obtained with autumn precipitation anomalies for the entire calibration period (1900-2002) and for the two halve subperiods (1910–1956 and 1957–2002). The applied statistical tests yield highly significant results. The obtained regression model explained 15.5% (R2-value for the full calibration period) of the September to November precipitation variability. The obtained transfer function allowed inferring past autumn precipitation from calcium carbonate sublayer thickness at annual resolution. The reconstructed series (PPT-SON) provides the first estimations of regional autumn precipitation shifts in the Central Pyrenees since 1500 CE