Preface
Decadal climate variability is currently an area of considerable scientific
interest whose importance is likely to grow over the next decade. Climate
Change on decadal time scales can result, for example, from changes in
the concentration of radiatively active gasses but also from natural variations. The causes of natural variability of the climate system on decadal
time scales are presently not well known; understanding the mechanisms
is however a prerequisite for any climate prediction of changes on these
time scales. To this extent a major new experiment, called CLIVAR,
has recently been launched by the World Climate Research Programme
to determine climate predictability both globally and regionally, and to
understand the physical processes giving rise to that predictability. The
time scales of interest range from seasons to decades and centuries, and
include phenomena such as El Nino Southern Oscillation and the North
Atlantic Oscillation, but also long-term changes in the ocean thermohaline
circulation.
The purpose of the NATO Advanced Study Institute, which was held
in February 1995 in Les Houches, France was to introduce young scientists
into the current state of the field. The focus was on modelling, analysing
and understanding of ocean-atmospheric interactions, primarily on decadal
time scales, although these can not be well separated from both shorter and
longer time scale processes. Major topics addressed were observed characteristic patterns of natural variability on decadal time scales in the coupled
atmosphere-ocean system, the generation mechanisms which are presently
not well understood, the potential predictability of long-term variability,
the possibility of rapid climate regime shifts on several times cales , the
causes for the large changes taking place at the present time in the northern seas of the Atlantic ocean.
A number of mechanism which are most likely to cause decadal variability have been proposed. Nonlinear interactions within the atmospheric circulation can, in the presence of orography and topography, induce low frequency variability of definite spatial organisation. Interaction with slower
components of the climate system (land, ocean, ice) can then produce
apparent lower frequency variability. Variability can also arise due to the
coupling of atmosphere and ocean. The variability due to El Nino-Southern
Ocean (EN SO) is one example of a coupled mode which primarily associated with interannual time scales, but can also have decadal variability.
Decadal climate variability is currently an area of considerable scientific
interest whose importance is likely to grow over the next decade. Climate
Change on decadal time scales can result, for example, from changes in
the concentration of radiatively active gasses but also from natural variations. The causes of natural variability of the climate system on decadal
time scales are presently not well known; understanding the mechanisms
is however a prerequisite for any climate prediction of changes on these
time scales. To this extent a major new experiment, called CLIVAR,
has recently been launched by the World Climate Research Programme
to determine climate predictability both globally and regionally, and to
understand the physical processes giving rise to that predictability. The
time scales of interest range from seasons to decades and centuries, and
include phenomena such as El Nino Southern Oscillation and the North
Atlantic Oscillation, but also long-term changes in the ocean thermohaline
circulation.
The purpose of the NATO Advanced Study Institute, which was held
in February 1995 in Les Houches, France was to introduce young scientists
into the current state of the field. The focus was on modelling, analysing
and understanding of ocean-atmospheric interactions, primarily on decadal
time scales, although these can not be well separated from both shorter and
longer time scale processes. Major topics addressed were observed characteristic patterns of natural variability on decadal time scales in the coupled
atmosphere-ocean system, the generation mechanisms which are presently
not well understood, the potential predictability of long-term variability,
the possibility of rapid climate regime shifts on several times cales , the
causes for the large changes taking place at the present time in the northern seas of the Atlantic ocean.
A number of mechanism which are most likely to cause decadal variability have been proposed. Nonlinear interactions within the atmospheric circulation can, in the presence of orography and topography, induce low frequency variability of definite spatial organisation. Interaction with slower
components of the climate system (land, ocean, ice) can then produce
apparent lower frequency variability. Variability can also arise due to the
coupling of atmosphere and ocean. The variability due to El Nino-Southern
Ocean (EN SO) is one example of a coupled mode which primarily associated with interannual time scales, but can also have decadal variability.