Denmark under IPCC scenarios – a view from the Eemian and Miocene past warm periods (EeMi)

The ‘most likely’ climate scenario according to the sixth assessment report of the Intergovernmental Panel on Climate Change (IPCC, AR6) predicts a CO2 concentration in the atmosphere of around 550 ppm by 2100 that will result in 2 to 3°C global warming. How this will play out in the climate system is widely discussed. In particular, the response of the Atlantic Meridional Ocean Circulation (AMOC) to warming, which has great implications for Danish mitigation and adaption strategies, is uncertain. Today, the AMOC is one of the key components of the global oceanic circulation and climate. The AMOC brings heat and moisture to Europe, and due to the upper limb of the AMOC (the Gulf Stream), Denmark is currently experiencing a mild and moist climate. Some studies propose, that a more-intense-than-present AMOC could increase both precipitation and temperature in Europe, while under a weaker AMOC, Europe would experience less rain and lower temperatures. The consequences of a decline will potentially induce a cascade of abrupt events related to the crossing of thresholds from different tipping points, not only locally, but globally.

The IPCC AR6 report has identified the Eemian and Miocene periods as “intervals of interest” due to their striking analogy with near future climate scenarios, the SSP1 “Sustainability/low CO2 emission” and SSP2 ”Middle of the road/intermediate CO2 emission”, respectively (SSP – Shared Socioeconomic Pathways). During the Eemian (130,000 to 115,000 years ago) the global temperature was 1-1.5°C higher than the preindustrial level due to high solar insolation. Similarly, during the Miocene Climatic Optimum (c. 17-15 million years ago), the atmospheric CO2 level was as high as today and the global temperature was 3-8°C higher than the preindustrial level. These two time periods can therefore help us to understand warmer-than-present climate states.

The objective of EeMi is to evaluate the climate state and variability in the northern middle latitudes (Danish North Sea) during the Eemian and the Miocene Climatic Optimum with a specific focus on reconstructing and assessing the state of the northern limb of the AMOC. We will utilize thick marine deposits and employ state-of-the-art paleoclimate proxy methods (biomarkers, such as: alkenones, membrane lipids, and leaf waxes) to reconstruct climate variability of sea surface temperature and precipitation during these two warmer-than-present climate states. We aim to generate the first high-resolution records from these time periods in the Danish North Sea and provide crucial data to validate model-based projections of future AMOC intensity, as well as temperature and precipitation patterns over Scandinavia.