Friday, May 2, 2014

New paper finds extreme precipitation and flooding in Spain were much worse in the past

A paper published today in Quaternary Science Reviews reconstructs precipitation of the Iberian Peninsula and finds the past 95 years from 1917-2012 experienced relatively low extreme precipitation and flooding in comparison to the past 665 years. The authors instead find two periods with much more frequent and extreme precipitation and flooding from 1347–1400 and 1844–1894 AD, which correlated to periods of relatively high solar activity. According to the authors, there is a "possible link of extreme rainfall to solar variability prior the 20th century."

Alarmists claim man is causing the climate to become more variable extreme, but hundreds of published paleoclimate studies indicate today's climate is less variable and quite benign in comparison to the rest of the Holocene [past ~11,000 years]. A warmer climate decreases the temperature differentials between the poles and the tropics, and since temperature differentials, not absolute temperatures, drive all weather phenomena, a warmer climate will be a more benign climate with less extreme weather. 

Solar activity shown in 2nd graph from top. Grey bands indicate periods with the highest frequency of extreme precipitation and flooding. 


An annual record of extreme rainfall from Lake Montcortès (NE Iberian Peninsula).
Quantitative rainfall threshold achieved for various detrital micro-facies.
Maxima in extreme rainfall events during the periods AD 1347–1400 and AD 1844–1894.
Minimum extreme rainfall at AD 1441–1508, 1547–1592, 1656–1712, 1765–1822, 1917–2012.
Possible link of extreme rainfall to solar variability prior the 20th century.


We present an annual reconstruction of extreme rainfall events interpreted from detrital layers and turbidites interbedded within a varved sediment record since the 14th century in Montcortés Lake (NE Spain, 1027 m a.s.l.). Clastic microfacies intercalated within the biochemical calcite varves were characterized and their depositional dynamics interpreted using high-resolution geochemical and sedimentological analyses. Annual number of detrital layers was compared against instrumental records of extreme daily rainfalls providing minimum rainfall thresholds and return periods associated to the identified types of clastic microfacies. Non-continuous detrital layers were deposited during rainfall events higher than 80 mm (>2-year return period) while graded detrital layers and turbidites were associated with higher magnitude rainfall events (>90 mm and >4-year return period). The frequency distribution of extreme hydro-meteorological events is not stationary and its pattern coincides with historical floods from the nearby Segre River. High frequency of heavy rainfalls occurred during the periods AD 1347–1400 and AD 1844–1894. A lower frequency of heavy rainfall was found during the periods AD 1441–1508, 1547–1592, 1656–1712, 1765–1822 and 1917–2012. The 20th century stands out as the longest interval within the studied period of very low number of extreme rainfall events. Variability in extreme rainfall events prior to the 20th century is in phase with solar activity, suggesting a mechanistic link in mid-latitude atmospheric circulation patterns that ceased during the 20thcentury.

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