chapter - Atmospheric and Oceanic Science

1.1. Dropping the hypothesis of stationary climate
There is climate variability in almost all scales of time. In some of them, climatic
variability come from processes of intrinsically random nature or are caused
by multiple and complex processes that hamper its prediction. Hence, the use of the
climate information is fundamentally based on the statistical analysis of its series.
Up to not long ago, many of the uses of the climatic information, rested on the
premise that the climate was stationary, at least at decadal scale, and so future climate
would be similar to that of the immediate past. Therefore, the series of climatic
elements and their hydrological derivates' were statistically treated as stationary.
Nowadays, the hypothesis that climatic series or their derivates are stationary
does not seem quite appropriate. Every time there are less doubts that the planet has
entered in a rapid climatic change induced by human activities. In consequence the
hypothesis almost always implicit that the statistics of the past climate can represent
those of the future climate it is no longer valid. The whole methodological arsenal
that was based on this simple presumption for the calculation of parameters of
design of infrastructures, the planning of the use of the water resources, of the territory,
of the forest activity or of the agriculture to medium term should be revised.
In some regions and for certain parameters, the climatic series are already no
longer stationary. For the cases that are still stationary, neither is a wise attitude to
suppose, a priori and without further analysis, they will continue being so. In consequence,
the estimate of some or several features of the future climate for some
planning requirement can no longer relay in the comfortable hypothesis that the climate
is stationary and therefore new methods are required. In spite of this necessity,
there still is not a completely developed and sure methodology to estimate the
future climate. Indeed, the great challenge for the world climatology during next
years will be to develop the methods to predict the climate of next decades in view
of the man induced climatic change.
8
CHAPTER
INTRODUCTION
Vicente Barros 1
1 CIMA/CONICET. University of Buenos Aires.
I