The third event in our Distinguished Geography Seminar series took place on Thursday, 9 June, with Prof. Guy P. Brasseur from Max Planck Institute for Meteorology, Hamburg, Germany and National Center for Atmospheric Research, Boulder, CO, USA as the invited guest speaker. Prof. Brasseur, a meteorologist and climate scientist, gave an insightful talk entitled " A historical journey to discover the mysteries of air " showing how atmospheric science has progressed over the centuries,  from ancient Greece to the Renaissance and finally to the 20th century. Over the course of this historical journey, air pressure was measured and the first laws of hydrodynamics were established. In the 1600’s, air was found to be composed of different gases. After the chemical revolution in 18th century, ozone and its presence were discovered in the 19th century and minor constituents were identified until the 20th century. A lively discussion took place in the Q&A section. The talk was well-attended by colleagues, students and friends of the department from around the world. The Webinar was moderated by Dr Meng Gao.