Research topics and projects

Feedbacks between geosphere, biosphere, atmosphere and ocean lead to timescale and state-dependent Earth system sensitivity and climate variability. These feedbacks have operated in the past, and led to substantial changes in surface temperature, precipitation, and topography, partly mediated by volcanism.

We investigate the cross-scale impacts of changes in boundary conditions on weather, climate and the carbon cycle by simulations with Earth system models of varying complexity. Generally, different models are employed for deep-time periods than for close-to-present-day conditions, with a varying range of feedbacks. We aim to test the impacts of this by experiments across a range of boundary conditions and levels of model complexity. A key element in our working philosophy are tracers for water isotope changes, and vegetation. These allow us to bridge between models (i.e. our understanding of the physical, biological, chemical interactions written down in formulae) and what actually can be observed in our one and only Earth system. The abundance of stable water isotopologues (i.e. water molecules with different molecular masses for the hydrogen and oxygen atoms) is affected by the movement and phase changes of water through the Earth system. This isotope variability can be measured on natural palaeoclimate archives (ice, speleothems, trees, foraminifera), as well as modeled by isotope-enabled general circulation models. Similarly, vegetation affects weather and climate, and is impacted by it at different timescales. We combine tracers and models to evaluate to what extent feedbacks can indeed be taken to operate on individual scales, and at which temporal and spatial scales isotopic tracers can inform on changes in boundary conditions and climate.

Research Projects

State and timescale-dependency of climate variability from the last Glacial to present day (STACY)

Palaeoclimate modeling: From the last Interglacial to the Anthropocene (PalMod), Phase III

Negative Emission Technologies based on Photoelectrochemical Methods

NFDI4Earth Pilot "Propagating complex uncertainties in data cubes"

#ZukunftslaborErde

Finished projects:

Resilienz³
Palaeoclimate modeling: From the last Interglacial to the Anthropocene (PalMod), Phase II
Constraining the Climatic Signal Archived in Water Isotopes in Antarctic Ice Cores (CLIMAIC)

Major Research Topics

Sustainable Pathways, Carbon Cycle Dynamics, and Climate Change Impacts

Climate–carbon cycle–biosphere interactions, Carbon dioxide removal, Societal transformation, Decarbonization, Economic consequences of climate change

Contributing to sustainable pathways into the future is a key mission of the SPACY group. In this research area, we focus on a key aspect of sustainable development under climate change: interactions between the carbon cycle, the climate and the Earth-Society system.

Main research questions

How can artificial carbon dioxide removal from the atmosphere support sustainable transformations? How can it impede development goals?
How accurate are Earth system models in capturing the response of vegetation to climate and carbon dioxide changes and how can we improve their description of the biosphere?
How do climate change and climate variability affect societies and economies?
Could new plant species combinations help to increase the CO2 fixation from the atmosphere?

More information on our work & ideas for thesis projects

Climate variability and extremes

Statistics and mechanisms of climate variability and their implications on extremes and projections

Investigating the causes and structure of climate variability across spatial and temporal scales is a key mission of the SPACY group and the focus of the team variability and extremes.

We investigate:

the reliability of climate variability estimates from paleoclimate archives and observations across temporal scales from years to several thousand of years
the causes of climate variability and its dependency on the mean climate state
the ability of climate models to reliably simulate local to global climate variability in the past and future
the role of climate variability in future projections, including the impact on extremes

More information on our work & ideas for thesis projects

The left panel shows the main components (hydrosphere, atmosphere, biosphere, lithosphere, and cryosphere) and drivers (volcanic aerosols, solar irradiance, greenhouse gas emissions, and orbital forcing) of Earth’s climate system. The right panel highlights characteristic timescales for some system-inherent processes (orange) and external drivers (blue). The figure uses estimates from the PALAEOSENS Project Members, 2012; Peixoto & Oort, 1992, and Rohling et al., 2018, as well as icons from flaticon.com.

Climate Modeling

Model development and evaluation, simulation setup and execution, application of machine learning methods to climate science

Climate models represent the climate system’s components and mechanisms numerically. They rest upon physical principles and approximations for hardly resolvable process chains (“parametrizations“). As such, they provide a laboratory for investigating climate at all times during Earth’s past and future.

We employ models of varying complexity to analyze the climate system on various scales in time and space. Our model development focuses on including new processes or modeling processes in more detail, especially for simulating land use and isotopes. These developments help us improve the quality of simulations since they implement processes that are crucial for future projections (land use, carbon dioxide removal) and because they provide a direct way of comparing simulations of climate’s past to past climate data. We carry out experiments simulating conditions at varying times in Earth’s history and future as well as idealized experiments aimed at furthering the understanding of the Earth System.

The variety of topics that can be explored with models is immense. As such, they contribute to all other research areas in our group.

More information on our work & ideas for thesis projects

This figure depict a globe with a mesh grid. A triangle is cut out from it with grid cells in various colors, i.e. green, blue, brown and white. A zoom shows one of the cells as a rectangular box containing elements, drivers and processes of the climate system. A sun illuminates the box from top and is marked with the text “solar radiation”, one of the drivers of climate. In the box there is the atmosphere above a large body of water marked as hydrosphere and with swimming ice marked as the cryosphere. The ocean is bordered by the land of the lithosphere. On land there are mountains, including a volcano spewing volcanic aerosols, trees as part of the biosphere as well as man-made structures, like factories emitting greenhouse gases in clouds of smoke and agricultural fields symbolizing land use. The aerosols and greenhouse gas emissions as well as land use changes are drivers of climate change. In the atmosphere and ocean, various processes active in the climate system are marked: clouds, wind, precipitation (e.g. rainfall), sea level, back radiation from the surface, ocean currents, sea ice, evaporation of water, weathering of rocks and mountains, the carbon cycle, and runoff from rivers and lakes. Additional text says “Figure copyright Beatrice Ellerhoff”.

Isotopes

With aims to understand the paleoclimate, atmospheric dynamics, and geochemical processes in caves we study oxygen isotopes in precipitation, cave dripwater and speleothems; and multiproxies in sediments and secondary carbonates.

Water isotopologues, i.e. the ratio between the more abundant H216O and the heavier H218O, are an important tracer of the hydrological cycle. These ratios change at phase changes along the moisture path of water parcels and can reveal important information on the dynamics of the climate system. One key research in the SPACY group is to decipher the diverse influences on these ratios from climate archives, such as speleothems, ice cores, shelf ice, and wood, but also from precipitation and drip water monitoring.

Main research topics

Paleoclimate and paleoenvironmental reconstructions based on speleothems and other cave materials
Effects of climate on the isotopic composition of rainwater from Tübingen and other sites in Southern Germany
We study the atmospheric dynamics and trace (extreme) weather events by studding isotopic composition in precipitation
We monitor the microclimate and geochemical conditions of cave environment and its surroundings
We explore worldwide isotope data in databases (SISAL, Iso2k, etc) and comparison with climate models

Joining the SPACY group for thesis projects

If you are excited about our research, we'd love to discuss project ideas with you. Just e-mail us (Prof. Kira Rehfeld and the SPACY group) and send us a short CV, tell us about your area of interest, your study record, and the rough timing you envisage. Bachelor theses and Master's scientific practice typically start around November 1st or May 1st. Please confirm your thesis with us one month prior to the starting date. While not strictly required, including your CV or other documents when reaching out can give us a better idea of your studies and interests.

Some of our thesis ideas involve a lot of modeling/programming, whereas others focus on lab work. You can find a couple of projects we are currently offering on our research pages. Courses that prepare you well cover, for example, climate dynamics, time series analysis, or programming (the SPACY group's course offerings are here). However, you can also contact us if you want to develop skills in your thesis work that you don't already have – research is about learning new, exciting things and abilities. As an interdisciplinary team of environmental scientists, geologists, meteorologists, geographers and physicist, we look forward to hearing from you and develop a project that suits your interests and skills.