final_program_abstracts[1]

11 IMSC Session Program
Memory in climate and things not to be forgotten
Wednesday - Plenary Session 10
Demetris Koutsoyiannis
Department of Water Resources and Environmental Engineering, Faculty of Civil
Engineering, National Technical University of Athens, Zographou, Greece
Forgetting some fundamental issues related to climate may have detrimental effects in
its research. A first issue that need not be forgotten is the fact that the very notion of
climate relies on statistics. For example, according to a popular definition (U.S.
Global Change Research Program: Climate Literacy, The Essential Principles of
Climate Sciences, 2009), climate is the long-term average of conditions in the
atmosphere, ocean, and ice sheets and sea ice described by statistics, such as means
and extremes. In turn, long-term average conditions cannot be assessed correctly if
inappropriate statistical models and assumptions are used. For example, statistical
methods commonly used in climate research are based on the classical statistical
paradigm that assumes independence of processes in time, or on the slightly modified
model of Markovian dependence. However, substantial evidence has been
accumulated from long time series, observed or proxy, that climate is characterized by
long-term persistence, also known as long memory or long-range dependence. Such
behaviour needs to be described by processes of Hurst-Kolmogorov type, rather than
by independent or Markovian processes. Consequently, it should be remembered that
the Hurst-Kolmogorov dynamics implies dramatically higher uncertainty of statistical
parameters of location and high negative bias of statistical parameters of dispersion. It
also implies change at all scales, thus contradicting the misperception of a static
climate and making redundant the overly used term “climate change”. The
fundamental mathematical properties of Hurst-Kolmogorov processes is another issue
that must not be forgotten, in order to avoid incorrect or misleading results about
climate.
Abstracts 160