Jochem Marotzke

I am interested in climate variability and especially the role of the ocean in climate, climate variability, and climatic change. Together with my research students, post-docs, and collaborators I try to tackle the fundamentals of how these things work . My approach to research has been characterised by two recurrent themes: I have to the extent possible used both models and observations, and I have employed the whole spectrum of ocean and climate models, from the fully comprehensive to the highly idealised.

The phenomenon that has dominated my research more than anything else has been the Meridional Overturning Circulation (MOC) in the Atlantic, sometimes also known under the less accurate name of Thermohaline Circulation (THC, driven by surface heat and freshwater fluxes). My unwavering fascination for the Atlantic MOC arises both from its climatic importance – the MOC-induced heat transport is responsible for Europe's unusually mild climate, given its geographical location – and from the MOC's complex variability and potential for abrupt change.

Prior to moving to Hamburg, I led the UK effort to establish the national programme RAPID, which as its cornerstone installed the first monitoring system for the Atlantic MOC, at 26.5° N; (see RAPID-MOC). For a while, I still participated in the RAPID fieldwork and, through students and post-docs, the data analysis, although I found it increasingly difficult to find the time to go to sea myself.

The possibilities at MPI-M, in particular its staff and its history of state-of-the-art climate modelling, have enabled me to expand my interests significantly beyond pure large-scale physical oceanography. Some of my students here have worked on extreme climates of the past – the Snowball Earth or the Palaeocene-Eocene Thermal Maximum – or have investigated potential extreme climates of the future or on other planets – the Runaway Greenhouse. These research areas draw a particular benefit from the combination of simple and complex models.

The combination of modelling and observations, on the other hand, provides a fertile ground for the research field of multi-year to decadal climate prediction. I proposed to the German Ministry for Education in Research in 2007 to establish a national programme on decadal climate prediction. I led this programme, called MiKlip, throughout its duration from 2011 to 2019; the prediction system we developed was transferred to the German meteorological service DWD where decadal predictions are now carried out operationally.

A small but extremely exciting portion of my research activity is filled by a collaboration with Prof. Manfred Milinski from the MPI for Evolutionary Biology, a collaboration that arose from a chance encounter at an annual meeting of the Max Planck Society. We perform laboratory experiments in which our human subjects play for real money – giving us insight into the conditions under which people are willing to invest into climate protection.

More recently, my interests in exploring the interactions between climate and social dynamics have broadened, and I have been one of the co-spokespersons of the Cluster of Excellence Climate, Climatic Change, and Society (CLICCS), led by Universität Hamburg.