Nir Joseph Shaviv (Hebrew: ניר יוסף שביב; born July 6, 1972) is an Israeli‐American physics professor.

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 1999, Shaviv has shown that inhomogeneities in stellar atmospheres reduce the effective opacity and thus increase the Eddington luminosity.

In a more recent work with Andreas Prokoph and Ján Veizer,[13] it was argued that the reconstructed temperature has a clear 32 million year oscillation that is consistent with the solar system's motion perpendicular to the galactic plane.

[16][non-primary source needed] Shaviv's solar hypothesis has been disputed by Mike Lockwood and Claus Froehlich (1936–2019)[17] in an analysis of the sun's output over the last 25 years.

[19] Firstly, while sunspot activity declined after 1985, cosmic ray flux reached a minimum in 1992 and contributed to warming during the 1990s.

Secondly, Shaviv argues that short term variations in radiative forcing are damped by the oceans, leading to a lag between changes in solar output and the effect on global temperatures.

[20] He claims that solar activity changes have contributed between half to two thirds of the warming over the 20th century,[21] and that climate sensitivity should be on the low side ΔTx2=1.3±0.4 °C compared with IPCC's range of ΔTx2=1.5 to 4.5 °C per CO2 doubling.

[23]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,[24] a book expressing climate change denial, which attracted considerable interest in Germany.