Friday, July 20, 2012

New paper finds cloudiness in Spain has significantly decreased since 1960

A paper published today in Climate of the Past finds that Total Cloud Cover (TCC) has significantly decreased over Spain by about 4% since 1960, the same period during which the IPCC claims there is no explanation other than man-made greenhouse gases to account for global warming. Poorly-understood natural fluctuations in cloud cover could alone account for global warming or global cooling, as discussed by Dr. Roy Spencer in his book
"The most obvious way for warming to be caused naturally is for small, natural fluctuations in the circulation patterns of the atmosphere and ocean to result in a 1% or 2% decrease in global cloud cover. Clouds are the Earth’s sunshade, and if cloud cover changes for any reason, you have global warming — or global cooling."
Until cloud effects are much better understood (as well as a host of other factors such as ocean oscillations), computer climate models will remain computer fantasy games. 

Estimated Total Cloud Cover (TCC) over Spain declined from 1961-2010
Full paper is available here

Clim. Past, 8, 1199-1212, 2012

Increasing cloud cover in the 20th century: review and new findings in Spain

A. Sanchez-Lorenzo1, J. Calb√≥2, and M. Wild1
1Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
2Group of Environmental Physics, University of Girona, Girona, Spain

 Abstract. Visual observations of clouds have been performed since the establishment of meteorological observatories during the early instrumental period, and have become more systematic and reliable after the mid-19th century due to the establishment of the first national weather services. During the last decades a large number of studies have documented the trends of the total cloud cover (TCC) and cloudy types; most of these studies focus on the trends since the second half of the 20th century. Due to the lower reliability of former observations, and the fact that most of this data is not accessible in digital format, there is a lack of studies focusing on the trends of cloudiness since the mid-19th century. In the first part, this work attempts to review previous studies analyzing TCC changes with information covering at least the first half of the 20th century. Then, the study analyses a database of cloudiness observations in Southern Europe (Spain) since the second half of the 19th century. Specifically, monthly TCC series were reconstructed since 1866 by means of a so-called parameter of cloudiness, calculated from the number of cloudless and overcast days. These estimated TCC series show a high interannual and decadal correlation with the observed TCC series originally measured in oktas. After assessing the temporal homogeneity of the estimated TCC series, the mean annual and seasonal series for the whole of Spain and several subregions were calculated. The mean annual TCC shows a general tendency to increase from the beginning of the series until the 1960s; at this point, the trend becomes negative. The linear trend for the annual mean series, estimated over the 1866–2010 period, is a highly remarkable (and statistically significant) increase of +0.44% per decade, which implies an overall increase of more than +6% during the analyzed period. These results are in line with the majority of the trends observed in many areas of the world in previous studies, especially for the records before the 1950s when a widespread increase of TCC can been considered as a common feature.

 Final Revised Paper (PDF, 1578 KB)   Discussion Paper (CPD)   

Related: New paper finds sunshine has increased in Iran over past 26 years