Lennart Bengtsson

The 2009 Alfred Wegener Medal & Honorary Membership is awarded to Lennart Bengtsson for his original contributions to numerical weather prediction and climate modelling, creating model systems of world-leading quality.

Lennart Bengtsson has been a visionary in Numerical Weather Prediction (NWP), data assimilation, and climate modelling for well over thirty years. Not only has he contributed seminal research papers, he has also been the driving force behind the building of institutions and programmes and has thus provided an immense service to the scientific community and to society at large.

It was Lennart’s leadership that contributed essentially to the establishment of the European Centre for Medium-Range Weather Forecasts (ECMWF) and to ECMWF’s world-leading role in NWP. As head of research at ECMWF, he developed both scientific and operational aspects of NWP. His work on data assimilation laid the foundation for ECMWF having the best data assimilation system, thus the least initial error, leading to the best NWP system in the world. In his position as director of ECMWF, he became a symbol of progress in NWP (best NWP system; best forecast of hurricane growth rate; best forecast of extra-tropical cyclones).

Lennart recognised long before others the enormous potential of reanalysis. Under his directorship ECMWF conducted the first experimental reanalysis; subsequently Lennart led the ECMWF effort toward the ERA-15 reanalysis. Also as director of ECMWF, Lennart was a visionary in promoting dynamical seasonal prediction at ECMWF. Both reanalysis and seasonal prediction helped the main ECMWF mission of medium range (10-day) forecasts.

After Lennart went to the Max Planck Institute for Meteorology (MPI-M), he put the ECHAM climate model on the world map. MPI-M was already famous because of Klaus Hasselmann; Lennart’s development of ECHAM, derived from the ECMWF NWP model, meant that MPI-M also has one of the “best” climate models in the world. At Lennart’s 65th birthday party, Klaus Hasselmann joked that when Klaus used to visit ECMWF, Lennart would tell him that ECMWF had the best NWP model, and after Lennart came to MPI-M, he would tell him that MPI-M had the best climate model!

Even after his formal retirement from MPI-M, Lennart has continued to carry out world-class research on topics such as the hydrological cycle, hurricanes in global warming, and problems with reanalyses, to name just a few. Lennart was and still is involved with many programmes and institutions. He was a leading force in setting up the Climate Variability and Predictability (CLIVAR) Project of the World Climate Research Programme (WCRP). One of the important scientific questions that he has championed recently is to urge the modelling community to try to understand why the climate models are so different form each other and what is the mechanism in each model that is producing global warming – rather than simply and mindlessly running more and more models for longer and longer periods.

Because of his scientific oeuvre and his enormous impact on atmospheric and climate science, there is no one more deserving of EGU’s Alfred Wegener Medal than Professor Lennart Bengtsson.

Medal lecture video (Youtube) of the Alfred Wegener Medal given at the EGU General Assembly 2009.