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CNR: Alamanacco della Scienza


N. 20 - 14 dic 2011
ISSN 2037-4801

International info   a cura di Cecilia Migali


Homogenisation improves quality of historical climate records

Relocations, changes in instrumentation, shelters, recording hours, may bias climate data series, and those artificial changes often mask true climate signal. Thus, raw climate records should not be used for climate studies as they may contain non-climatic changes. Corrections to the data are needed to remove these non-climatic influences and this procedure is called homogenisation.

In order to study the performance of homogenisation methods, Cost Action Home, involving Cnr-Institute of Atmospheric Sciences and Climate (Isac), has performed a test with artificial climate data. The article describing this research has just been accepted by the journal Climate of the Past, an open-access and an open-review journal of the European Geosciences Union.

The advantage of artificial data is that the non-climatic changes are known to those who created the data. The artificial data mimic climatic networks and their data problems with unprecedented realism. The artificial data may have a warming, a cooling or no trend, to ensure objective testing of the methods.

The main novelty is that the test was blind. In other words, while homogenising the data the scientists did not know which station contained which non-climatic problem. The artificial data were generated and the analysis of results was performed by independent researchers, who did not homogenise the data themselves. Consequently, the Cost Action is sure that the results are an honest appraisal of the true power of homogenisation algorithms.

The results show that homogenisation improves the quality of temperature records and makes the estimate of climatic trends more accurate. For those genuinely sceptical of climate records that show warming, the results from the blind test are evidence that homogenisation does not bias climatic trends, but rather makes the estimates of the trends more accurate.

In the future, experience gained during Cost Action Home will be profitable for the international surface temperature initiative (Isti), which is working on an open and transparent framework for creating and hosting global temperature datasets.

This Cost Action included researchers from 27 Eu countries, as well as Andorra, Australia and Usa.



Fonte: Michele Brunetti, Istituto di scienze dell'atmosfera e del clima, Bologna, tel. +39 0516399623, email m.brunetti@isac.cnr.it