Fred L. Scarf Award for Kok Leng Yeo

American Geophysical Union honors MPS scientist for his contributions to climate research.

The American Geophysical Union (AGU) has chosen Dr. Kok Leng Yeo of the Max Planck Institute for Solar System Research (MPS) in Germany as this year’s winner of the Fred L. Scarf Award. With this prize, the AGU honors Yeo for his contributions to a better understanding of solar irradiance variations which are a significant factor in climate research and help to estimate the extent of the Sun’s impact on global climate. The Fred L. Scarf Award is awarded annually to distinguish an outstanding dissertation from the field of solar and planetary research.

Solar radiation is not always the same. The solar irradiance that impinges upon Earth varies on time scales ranging from days to centuries and, thus, influences global climate on our planet. “Undisturbed measurements of solar irradiance are only possible above the Earth’s atmosphere from space”, Kok Leng Yeo explains. “Suitable data therefore only exist since the beginning of the space age a few decades ago”, he adds. However, to understand the Sun’s long-term impact on global climate, a look has to be taken further back into time – and therefore at the Sun itself. Detailed observations of our star have existed for several centuries. But which changes on the Sun lead to variations in solar irradiance? And how can irradiance be derived from solar observations?

In his doctoral thesis, Yeo investigated exactly these questions. He was able to show the significance of comparatively small magnetic structures on the Sun for irradiance variations. In addition, he refined a model, which helped him to calculate the Sun’s irradiance from 1974 to this day with unprecedented precision. Due to the existence of space-based data from these years, this time period serves as a test for every theoretical model.

“Kok Leng Yeo’s work has furthered the research in this field significantly and acts as a stepping stone for future models that may be even more reliable”, say Prof. Dr. Sami K. Solanki, director of the MPS, and Dr. Natalie Krivova, leader of the MPS research group “Solar variability and climate”.

Kok Leng Yeo studied Astrophysics at the Imperial College in London. After graduating he worked in industry for six years before resuming his scientific career in 2010 at the MPS as a PhD student. He earned his doctorate in 2014 with a dissertation on “Analysis and modeling of solar irradiance variations”. Since then, he is part of the Minerva group “Solar variability and climate” at the Max Planck Institute for Solar System Research.