Back for the future – BMBF research programme PalMod III simulates the climate from the last warm period through the ice age into the future in order to better predict climate change

Prof. Lohmann, in your research as part of the BMBF's PalMod funding initiative, you are simulating the climate and its changes over the last 130,000 years. How can these simulations help to better predict the future of the climate?
So far, climate models have been extensively tested on shorter time scales. Now we are entering a new world in which, for example, the ice sheets on Greenland and the Antarctic can change massively. The carbon cycle also still has many surprises in store. In the PalMod project, we are developing innovative modelling systems that can depict these changes and make predictions for the future. We can then compare the simulations with the climate changes that have actually taken place over the last 130,000 years. If such tested systems are used for the future, we will have even more confidence in climate models.

The 1.5 degree target of the 2015 Paris Climate Agreement is most likely no longer achievable, what now?
To be honest: If we stay below 2 degrees, it would already be a success. I find it completely incomprehensible that the industrialised countries are not leading the way and focusing massively on renewable energies. The danger is far too great, that certain threshold values in the climate and ecosystem will be exceeded, which could lead to irreversible losses. These critical processes must be identified in research! Our project shows that compliance with the climate protection agreement is absolutely essential to ensure a sustainable future without major climate surprises.

What do you already know about the dynamics of climate change, what consequences could this development have for our lives?
The palaeoclimate gives us an insight into what can happen. Some animal and plant species will not be able to cope with rapid climate change and will have to migrate, while others will be able to adapt. There are also regions of the earth that will no longer exist in a warmer world, for example our Arctic, which is ice-covered even in summer. This not only has an impact on the weather as well as weather and climate extremes, but also directly on animals and plants. The consequences are still relatively unknown, and the models for an improved assessment of the consequences are still in their infancy. One important example is the sea level. In the last warm period, the climate was a few degrees warmer and the sea level was 4-9 metres higher than today. This shows how sensitive our earth system is. Bremen, Bremerhaven, Hamburg and Kiel would have major problems with this and would probably have to relocate.

Of what use is research that examines such a long period in the past for the future, when we already know today, what needs to be done? Namely, that climate change can only be curbed by a massive reduction in carbon dioxide (CO₂) emissions and the active removal of CO₂ from the atmosphere (CDR, Carbon Dioxide Removal).
We are researching the carbon reservoirs on earth: Where are they located? How are they changing? I myself was born, when the atmospheric CO₂ concentration was 320 ppm, now we are at over 420 ppm and it is rising. In the last ice age, we had about 180 ppm. We are expecting over 600 ppm, if mankind does not change course. The effects would be drastic and, in some cases, unpredictable.
For scientifically substantiated scenarios, we need models that can adequately capture the necessary complexity. Interactive ice sheets and carbon reservoirs in our new modelling systems enable feedbacks that are not yet really included in the current scenarios. Incidentally, I don't believe that everyone has realised that a massive reduction in greenhouse gas emissions is imminent. Most people are not interested in their ecological footprint, nor have politicians been setting convincing and consistent framework conditions for decades. Technical possibilities are being discussed, but this will not solve the carbon problem in the atmosphere any time soon. Our models can also tell us how much time we have left to find solutions.

What do you want to achieve and improve with the results of PalMod?
The research within the PalMod project is a milestone in palaeoclimate research because it raises the question: How did we get into the last ice age and how did we get out of it? From the past, we can gain insights into how processes in the atmosphere and the ocean influence today's ice sheets and thus the sea level. Coupled ice sheet climate models, such as those being developed by the PalMod project, will set a new standard for sea level projections under warming conditions. Models with interactive carbon reservoirs are already in use and their application to the climate of the earth's past is essential to understand and draw conclusions from the coupled climate-carbon system.

Professor Lohmann, thank you for the interview.