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Nir Shaviv
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Nir Joseph Shaviv (born 1972, in Ithaca, New York) is an Israeli/American physics professor, carrying out research in the fields of astrophysics and climate science. He is currently an associate professor at the Racah Institute of Physics of the Hebrew University of Jerusalem.
He is most well-known for his solar and cosmic rays hypothesis of 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.
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Encyclopedia
Nir Joseph Shaviv (born 1972, in Ithaca, New York) is an Israeli/American physics professor, carrying out research in the fields of astrophysics and climate science. He is currently an associate professor at the Racah Institute of Physics of the Hebrew University of Jerusalem.
He is most well-known for his solar and cosmic rays hypothesis of 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.
His most known contribution to the field of astrophysics was to demonstrate that the Eddington luminosity is not a strict limit, 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.
Shaviv was one of the global warming skeptics interviewed for The Great Global Warming Swindle documentary. In the film he states:
Solar variation
Shaviv’s solar hypothesis has been disputed by Mike Lockwood and Claus Froehlich in an analysis of the sun’s output over the last 25 years. They argue that the sun’s activity has been decreasing since 1985 while global temperatures have continued to rise.
Shaviv argues that Lockwood and Froehlich's analysis is flawed for a number of reasons. 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. While the 2001 maximum was weaker than the 1990 maximum, increasing solar activity during previous decades was still having a warming effect, not unlike the lag between noon and the hottest hour of the day.
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