PIK Biennial Report 2000-2001 - Potsdam Institute for Climate ...

Climate System
Head: Martin Claussen
Deputy Head: Friedrich-Wilhelm Gerstengarbe
Overview
Understanding the interplay between the various components
of the climate system is the key to a comprehensive
Earth system analysis. Therefore the Climate System
Department focuses on climate analysis and scenarios,
climate-system modelling and ocean modelling. The
research in these areas includes: i) the statistical analysis
of past and present-day climatic data as well as the construction
of future climate scenarios; ii) the development
of a climate-system model of intermediate complexity;
and iii) the investigation of ocean currents, in particular
ocean-atmosphere feedbacks.
Climate Analysis and Scenarios
Group leader: Friedrich-Wilhelm Gerstengarbe
A prerequisite for any research related to climate is a
thorough analysis of past and present-day climate based
on high-quality data. Therefore, a PIK DATA Base System
has been set up and is continuously expanded and
updated in co-operation with the Data & Computation
Department. The database contains high resolution, long
term time series from all relevant climate stations of the
world. Secondly, new multivariate statistical methods
have been developed which are used for climate data
analysis as well as for the validation of climate models.
For constructing regional climate change scenarios a new
method has been formulated. This method considers
results from climate models and observed regional climate
parameters. It is based on an expanded cluster analysis
algorithm and Monte Carlo simulations. The climate
change scenarios are used in all PIK projects related to
regional climate change.
Climate System Modelling
Group leader: Martin Claussen
In the Climate System Department a climate-system
model of intermediate complexity called CLIMBER-2
(for CLIMate and BiosphERe, version 2) has been developed.
It is used to focus on an efficient description of
the feedbacks between all major components of the natural
Earth system on time scales of centuries and millennia.
Examples are simulations of the last glacial cycle,
changes in carbon isotopes during the last 10,000 years,
the greening and aridification of Northern Africa, and an
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Martin Claussen
analysis of the effects of volcanism, solar variability and
land use on climate change of the past millennium.
CLIMBER-2 includes dynamic models of the atmosphere,
ocean, vegetation, and inland ice as well as models
of terrestrial and oceanic carbon cycles. Currently it is
the major tool used in the QUEST project.
For studies of the natural Earth system which require
higher spatial and temporal resolution, a new model
framework, CLIMBER-3, is under development in cooperation
with both the Global Change & Natural Systems
and the Data and Computation Departments.
Ocean Modelling
Group leader: Stefan Rahmstorf
Work in the ocean modelling group focuses on understanding
the role of the oceans and sea ice in climate
change, past and future. A major effort during the past
two years has gone into developing the ocean component
for the new coupled model CLIMBER-3. This
ocean component is based on the GFDL MOM-3
model, which has been extended in various aspects and
coupled to a state-of-the-art sea ice model. Further
development work has focused on coupling to the
atmosphere and on the implementation of an ocean carbon
cycle model. Scientific issues that have been looked
at were, for example, the role of sea ice in lowering the
carbon dioxide levels during glacial times, or the dynamics
of the Antarctic Circumpolar Current.
Another avenue of research is the development of simple
conceptual, stochastic models of oceanic processes
such as open ocean convection, to study aspects of their
nonlinear dynamics.