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.^[1]

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.^[2]

His best known contribution to the field of astrophysics was to demonstrate that the Eddington luminosity is not a strict limit,^[3] namely, that astrophysical objects can be brighter than the Eddington luminosity without blowing themselves apart. This is achieved through the development of a porous atmosphere that allows the radiation to escape while exerting little force on the gas. The theory was correctly used to explain the mass-loss in Eta Carinae's giant eruption, and the evolution of classical nova eruptions.^[4]

Shaviv started taking courses at the Israel Institute of Technology in Haifa at age 13.^[5] After a 3-year service in the IDF Unit 8200, he received in 1994 a Master of Science in physics and a doctorate during 1994–96. During 1996–99, he was a Lee DuBridge Prize Fellow at Caltech's TAPIR (Theoretical Astrophysics) group. During 1999–2001, he was in a postdoctorate position at the Canadian Institute for Theoretical Astrophysics. In 2001–2006, he was a senior lecturer at Racah Institute of physics at the Hebrew University of Jerusalem. In 2006–2012, he was an associate professor, and full professor since 2012. Between 2008 and 2011, he was the head of the faculty union of the Hebrew University, and he served as the chairman of coordinating council of faculty unions between 2010 and 2014. In 2014, he became a member of the Institute for Advanced Study in Princeton, and served as the chairman of The Racah Institute of Physics between 2015 and 2019.

Shaviv disagrees with the scientific consensus on human-caused climate change.^[19] He claims that solar activity changes have contributed between half to two thirds of the warming over the 20th century,^[20] and that climate sensitivity should be on the low side ΔT_x2=1.3±0.4 °C compared with IPCC's range of ΔT_x2=1.5 to 4.5 °C per CO₂ doubling.^[21]

Shaviv was interviewed for The Great Global Warming Swindle documentary. In the film he states:

A few years ago if you would ask me I would tell you it's CO₂. Why? Because just like everyone else in the public I listened to what the media had to say.^[22]

In 2012, he contributed, along with Werner Weber, Henrik Svensmark and Nicola Scafetta, to the book Die kalte Sonne. Warum die Klimakatastrophe nicht stattfindet (The Cold Sun) of Fritz Vahrenholt and Sebastian Lüning, a book expressing climate change denial, which attracted considerable interest in Germany.^[23] Numerous scientists criticised the book and considered its underlying assumptions to be either outdated or highly speculative.^{[24][25][26][27]}

In 2018, the German Bundestag's environment committee invited him as an expert to the German Parliament. There he denied that carbon dioxide had a substantial effect on climate change^[28] and claimed the Intergovernmental Panel on Climate Change (IPCC) was ignoring information that the sun was the primary cause for climate change.^[29]

Nir Shaviv has been a speaker for the Heartland Institute.^[30][31]

• 1996 Wolf foundation award for excellence as PhD student
• 1996 Lee A. DuBridge scholarship at Caltech
• 2000 Beatrice Tremaine scholarship in Toronto
• 2004 Siegfried Samuel Wolf lecture for nuclear physics
• 2014 IBM Einstein Fellowship, Institute for Advanced Study, Princeton

• Elphick, C; Regev, O. & Shaviv, Nir J (1992), "Dynamics of Fronts in Thermally Bistable Fluids", The Astrophysical Journal, 392 (1): 106, Bibcode:1992ApJ...392..106E, doi:10.1086/171410
• Shaviv, Nir J (1998), "Can Nonlinear Structure Form at the Era of Decoupling?", Mon. Not. R. Astron. Soc., 297 (4): 1245–1260, arXiv:astro-ph/9804292, Bibcode:1998MNRAS.297.1245S, doi:10.1046/j.1365-8711.1998.01602.x, S2CID 126440
• Dar, A; Laor, A. & Shaviv, Nir J (1998), "Life extinctions by cosmic ray jets", Physical Review Letters, 80 (26): 5813–5816, arXiv:astro-ph/9705008, Bibcode:1998PhRvL..80.5813D, doi:10.1103/PhysRevLett.80.5813, S2CID 14143132
• Shaviv, Nir J (2000), "The Porous Atmosphere of eta-Carinae", The Astrophysical Journal Letters, 532 (2): L137–L140, arXiv:astro-ph/0002212, Bibcode:2000ApJ...532L.137S, doi:10.1086/312585, PMID 10715243, S2CID 705762
• ———————— (2003), "The Spiral Structure of the Milky Way, Cosmic-Rays and Ice-Age Epochs on Earth", New Astronomy, 8 (1): 39–77, arXiv:astro-ph/0209252, Bibcode:2003NewA....8...39S, doi:10.1016/S1384-1076(02)00193-8, S2CID 879406
• ————————; Veizer, Ján (2003), "Celestial driver of Phanerozoic climate?", GSA Today, 13 (7): 4–10, doi:10.1130/1052-5173(2003)013<0004:CDOPC>2.0.CO;2
• ———————— (2005), "On Climate Response to Changes in the Cosmic Ray Flux and Radiative Budget", J. Geophys. Res. Space Phys., 110 (A8): A08105, arXiv:physics/0409123, Bibcode:2005JGRA..110.8105S, doi:10.1029/2004JA010866, S2CID 16364672
• Scherer, K; Fichtner, H; Borrmann, T; Beer, J; Desorgher, L; Flükiger, E; Fahr, H; Ferreira, SE; et al. (2006), "Interstellar-Terrestrial Relations: Variable Cosmic Environments, The Dynamic Heliosphere, and Their Imprints on Terrestrial Archives and Climate", Space Science Reviews, 127 (1–4): 327, Bibcode:2006SSRv..127..327S, doi:10.1007/s11214-006-9126-6, S2CID 119640116

• Shaviv, Nir J (August 2003), "Climate Change and the Cosmic Ray Connection", International Seminar on Nuclear War and Planetary Emergencies – 30th session, Erice, Italy: Ed. R. Ragaini, World Scientific (invited)