Nir Shaviv
Encyclopedia
Nir Joseph Shaviv is an Israel
i/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 also the head of the national coordinating council of faculty unions in Israel.
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 .
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:
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.
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
i/American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
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
Hebrew University of Jerusalem
The Hebrew University of Jerusalem ; ; abbreviated HUJI) is Israel's second-oldest university, after the Technion – Israel Institute of Technology. The Hebrew University has three campuses in Jerusalem and one in Rehovot. The world's largest Jewish studies library is located on its Edmond J...
.. He is also the head of the national coordinating council of faculty unions in Israel.
He is most well known for his solar and cosmic rays hypothesis of climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
. 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
Jan Veizer
Ján Veizer is the Distinguished University Professor of Earth Sciences at the University of Ottawa and Institute for Geology, Mineralogy und Geophysis, of Bochum Ruhr University, he held the NSERC/Noranda/CIFAR Industrial Chair in Earth System Isotope and Environmental Geochemistry until 2004...
, a low upper limit was placed on the climatic effect of .
His most known contribution to the field of astrophysics was to demonstrate that the Eddington luminosity
Eddington luminosity
The Eddington luminosity in a star is defined as the point where the gravitational force inwards equals the continuum radiation force outwards, assuming hydrostatic equilibrium and spherical symmetry. When exceeding the Eddington luminosity, a star would initiate a very intense continuum-driven...
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
Nova
A nova is a cataclysmic nuclear explosion in a star caused by the accretion of hydrogen on to the surface of a white dwarf star, which ignites and starts nuclear fusion in a runaway manner...
eruptions.
Shaviv was one of the global warming skeptics interviewed for The Great Global Warming Swindle
The Great Global Warming Swindle
The Great Global Warming Swindle is a polemical documentary film that suggests that the scientific opinion on climate change is influenced by funding and political factors, and questions whether scientific consensus on anthropogenic global warming exists....
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.
Education
Shaviv studied 1987-1990 physics at the Israel Institute of Technology in Haifa and finished his BA as best in class. During his military service (1990–93) he continued his studies 1992 and coauthored his first papers in astrophysics. 1994 he received a Master of Science in physics and a doctorate 1994 - 1996. 1996 - 1999 he was Lee DuBridge Prize Fellow at Caltechs TAPIR (Theoretical Astrophysics Group). 1999-2001 he was in a Postdoc position at the university of Toronto and 2001-2006 as senior lecturer at Racah Institut of physics at University of Jerusalem.Prizes
- 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
Lectures (Selection)
- N. J. Shaviv, “Climate Change and the Cosmic Ray Connection”, in “International Seminar on Nuclear War and Planetary Emergencies – 30thsession”, Erice, Italy, August 2003. (Ed. R. Ragaini, World Scientific, 2004) (invited)
See also
External links
- Sciencebits.com, Shaviv's weblog
- Shaviv's home page at the Hebrew University