In attempting to account for long-term paleoclimatic variations, we are led to broaden our view of the climate system and to restructure our approach to a fuller theory of climate. We begin by describing the external forcing of the climate system and the observed response, as represented by proxy evidence for paleoclimatic variations. One focus of the course is to identify driving mechanisms for climate change. This is done through numerical models of the Earth system and statistical analysis of instrumental and proxy data. Special areas: feedback mechanisms in the climate system; the role of the global oceanic thermohaline circulation for paleo and recent climate variations; deglaciation; Holocene climate; Glacial climate; Climate modes like ENSO and NAO; Milankovitch theory of the ice ages.

Further Literature:

• Dynamical Paleoclimatology - a generalized theory of global climate change, B. Saltzman, Academic Press, San Diego, 2002, 345 pp.
• The nature of mathematical modeling, N. Gershenfeld, Cambridge University Press, Cambridge, 2003, 344 pp.
• Earth's Climate Past and Future <http://www.whfreeman.com/ruddiman/>, by William F. Ruddiman

Students are recommended to read chapter 6 in the latest IPCC report (pdf) before the course starts.

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2. Kurs:

Holocene climate variability

It is of vital importance to understand whether increasing human population and industrialization have already caused, or have the potential to induce significant changes in earth's climate. In order to properly address this question, one needs quantitative information regarding the amplitude and rapidity of natural variations of temperature in the ocean, over the continents, and in the cryosphere. The best way to ascertain the extent of past changes is through the inspection of historical time series of direct temperature measurements or documentation of such environmental observations.

Unfortunately, the type of direct temperature measurement records which would allow one to quantify climate changes on a global scale are too short, and they fall already within the period of strong human impact on natural conditions. Information regarding the pre-anthropogenic state of the system can be obtained either from proxies that record past climate and environmental conditions, or by simulating climate using comprehensive models of the climate system under appropriate external forcing changes. The paleoclimate record provides an excellent test of these models as it reveals climate variations that have actually occurred in the past.

For the paleoclimate dynamics, one can bring together Earth System Modeling, statistical analyses of historical and proxy data, as well as work with conceptual models. These directions of research are reflected by our research onto Holocene climate variability. One goal is to bring the specialists from the modeling and the archive communities together. In the following, the specifics of research activities are described:

Analysis of Characteristical Pattern and Time Scales of Atmospheric Variability
http://www.awi.de/fileadmin/user_upload/Research/Research_Divisions/Climate_Sciences/Paleoclimate_Dynamics/Modelling/Concept/AOSignature.pdf

Felis, T., G. Lohmann, H. Kuhnert, S. Lorenz, D. Scholz, J. Pätzold, S.
A. Al-Rousan, S. M. Al-Moghrabi, 2004: Increased seasonality in Middle
East temperatures during the last interglacial period.Nature Vol. 429,13 MAY 2004, 164-168.
http://www.geo.uni-bremen.de/geomod/staff/gerrit/eem/Eem.html

Lorenz, S., and Lohmann, G., 2004: Acceleration technique for
Milankovitch typeforcing in a coupled atmosphere-ocean circulation
model:method and application for the Holocene. Climate Dyn., Volume 23,
Numbers 7-8, pp. 727-743. doi:10.1007/s00382-004-0469-y.
http://www.geo.uni-bremen.de/geomod/staff/gerrit/abstractAcBounCond.html


Lorenz, S. J., J.-H. Kim, N. Rimbu, R. R. Schneider, and G. Lohmann,
2006: Orbitally driven insolation forcing on Holocene climate trends:
evidence from alkenone data and climate modeling, Paleoceanography,
21,  PA1002,  doi:10.1029/2005PA001152
http://www.geo.uni-bremen.de/geomod/staff/gerrit/abstractAlke06.html

Herold, M, G. Lohmann, 2009: Eemian tropical and subtropical African moisture
modelling study. Climate Dynamics, doi:10.1007/s00382-008-0515-2 http://www.awi.de/fileadmin/user_upload/Research/Research_Divisions/Climate_Sciences/Paleoclimate_Dynamics/NewManuscripts/fulltext_01.pdf


Laepple, T., G. Lohmann, 2009:
The seasonal cycle as template for climate variability on astronomical timescales: A conceptual model. Paleoceanography

Rimbu, N., Lohmann, G., Grosfeld, K., 2007: Northern Hemisphere atmospheric blocking in ice core accumulation records from northern Greenland, Geophysical Research Letters, 34, LO9704, doi:10.1029/2006GL029175 (pdf)