"Emma Järvinen's award is a strong sign of the international visibility and scientific excellence of the University of Wuppertal," says Prof Dr Stefan Kirsch, Vice-Rector for Research and Digital Affairs. And Rector Prof Dr Birgitta Wolff adds: "The fifth ERC success story for our university within a year is a wonderful Christmas present. It can go on like this."

Järvinen's project centres on one of the greatest challenges in climate research: the precise determination of the effect of ice clouds on the Earth's climate. These so-called cirrus clouds consist of tiny ice crystals and influence the Earth's temperature in complex ways - they can both cool the Earth by scattering sunlight back into space and warm it by retaining heat radiation. Which effect predominates depends on numerous factors, including the microstructure of the ice crystals themselves.

Innovative approach: nano-structures of ice crystals come into focus

Only recent observations from the laboratory, aircraft measurements and satellites have shown that nano- and microscopic structures on the crystal surfaces - such as roughness or tiny air pockets - have a decisive influence on how ice crystals scatter light. However, these structures are hardly taken into account in today's numerical climate models. This leads to significant discrepancies between model calculations and real measurements.

This is where CRYSTAL comes in: For the first time, a method established in technical optics for describing surface roughness is being transferred to atmospheric ice crystals. Järvinen combines state-of-the-art 3D nanoprinting processes, which can be used to artificially recreate realistic ice surfaces, with measurements from a newly developed polarimeter (editor's note: a polarimeter is a measuring device that measures the polarisation of light. This means that it recognises the direction in which the light waves oscillate), which measures directly in ice clouds on board research aircraft. The result is a physically realistic optical model that describes the light scattering of rough ice crystals much more accurately than previous approaches.

Major significance for climate forecasts

The results are crucial for the next generation of earth observation satellites such as NASA PACE and EUMETSAT Metop-SG. Their high-precision instruments require reliable optical models of the ice crystals in order to correctly derive important climate parameters such as ice water content or particle size. CRYSTAL closes a key knowledge gap here.

The new models should make climate predictions more reliable in future - an important step towards providing a better scientific basis for political decisions and adaptation strategies. Järvinen's research could also be relevant for potential geoengineering approaches that aim to specifically influence ice clouds.

"This is the first time we have replicated real ice particle surfaces using 3D nanoprinting. Combining this lab work with targeted measurements using innovative technologies on a research aircraft forms a unique lab-to-field model validation chain," explains Emma Järvinen. "The goal is that after five years we will be able to confidently incorporate the optical properties of ice crystals into climate models and reliably interpret satellite data."