Nir Joseph Shaviv (Hebrew: ניר יוסף שביב, born July 6, 1972) is an Israeli‐American physics professor. He is professor at the Racah Institute of Physics of the Hebrew University of Jerusalem. He is known for his solar and cosmic-ray hypothesis of climate change which disagrees with the scientific consensus on human-caused climate change. In 2002, Shaviv hypothesised that passages through the Milky Way's spiral arms appear to have been the cause behind the major ice-ages over the past billion years. In his later work, co-authored by Jan Veizer, a low upper limit was placed on the climatic effect of CO2.