Nir Shaviv
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Nir Joseph Shaviv (; born July 6, 1972) is an
Israel Israel, officially the State of Israel, is a country in West Asia. It Borders of Israel, shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. Isr ...
i‐
American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, p ...
physics Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
professor. He is
professor Professor (commonly abbreviated as Prof.) is an Academy, academic rank at university, universities and other tertiary education, post-secondary education and research institutions in most countries. Literally, ''professor'' derives from Latin ...
at
the Racah Institute of Physics The Racah Institute of Physics () is an institute at the Hebrew University of Jerusalem, part of the faculty of Mathematics and Natural Sciences on the Edmund J. Safra Campus in the Givat Ram neighborhood of Jerusalem. The institute is the cente ...
of the
Hebrew University of Jerusalem The Hebrew University of Jerusalem (HUJI; ) is an Israeli public university, public research university based in Jerusalem. Co-founded by Albert Einstein and Chaim Weizmann in July 1918, the public university officially opened on 1 April 1925. ...
. He is known for his solar and
cosmic-ray Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Sol ...
hypothesis of
climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
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 . His best known contribution to the field of astrophysics was to demonstrate that the
Eddington luminosity The Eddington luminosity, also referred to as the Eddington limit, is the maximum luminosity a body (such as a star) can achieve when there is balance between the force of radiation acting outward and the gravitational force acting inward. The stat ...
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 η Carinae (Eta Carinae, abbreviated to η Car), formerly known as η Argus, is a stellar system containing at least two stars with a combined luminosity greater than five million times that of the Sun, located around ...
's giant eruption, and the evolution of classical
nova A nova ( novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", Latin for "new") that slowly fades over weeks or months. All observed novae involve white ...
eruptions.


Education and career

Shaviv started taking courses at the
Israel Institute of Technology Israel, officially the State of Israel, is a country in West Asia. It shares borders with Lebanon to the north, Syria to the north-east, Jordan to the east, Egypt to the south-west, and the Mediterranean Sea to the west. It occupies the Pale ...
in Haifa at age 13. 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 The California Institute of Technology (branded as Caltech) is a private university, private research university in Pasadena, California, United States. The university is responsible for many modern scientific advancements and is among a small g ...
's TAPIR (Theoretical Astrophysics) group. During 1999–2001, he was in a postdoctorate position at the
Canadian Institute for Theoretical Astrophysics The Canadian Institute for Theoretical Astrophysics (CITA) is a national research institute funded by the Natural Sciences and Engineering Research Council, located at the University of Toronto in Toronto, Ontario, Canada. CITA's mission is "to f ...
. 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 The Institute for Advanced Study (IAS) is an independent center for theoretical research and intellectual inquiry located in Princeton, New Jersey. It has served as the academic home of internationally preeminent scholars, including Albert Ein ...
in Princeton, and served as the chairman of
The Racah Institute of Physics The Racah Institute of Physics () is an institute at the Hebrew University of Jerusalem, part of the faculty of Mathematics and Natural Sciences on the Edmund J. Safra Campus in the Givat Ram neighborhood of Jerusalem. The institute is the cente ...
between 2015 and 2019.


Scientific research


Eddington luminosity limit

In 1999, Shaviv has shown that inhomogeneities in stellar atmospheres reduce the effective opacity and thus increase the Eddington luminosity. Shaviv later showed that atmospheres are inherently unstable as the Eddington luminosity is approached, that these atmospheres will develop continuum driven winds that explain the appearance of eta-Carinae and classical nova eruptions. In 2010, Shaviv made the prediction that Type IIn supernova should have super-Eddington outbursts before the main supernova explosions since the super-Eddington states can naturally explain the circum-stellar material present around the supernova at the time of explosion (Giving the narrow lines observed in the spectrum, i.e., the “n” in the Type IIn). Such precursors were later detected with the Palomar Transient Factory, making them the first systematically detected supernova precursors.


Cosmic rays and climate

Shaviv has been one of the proponents of a
cosmic ray Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the ...
climate link. In 2003 he has shown that the cosmic ray flux over the past billion years can be reconstructed from the exposure ages of Iron meteorites, that these flux variations are expected from spiral arm passages, and they correlate with the appearance of ice age epochs on Earth. In a later work with Ján Veizer, it was demonstrated that the temperature reconstruction over the Phanerozoic correlates with the cosmic ray flux, but it does not correlate with the reconstruction, thus placing an upper limit on the effects of . This prompted several reactions by the climate community and rebuttals by Shaviv and his colleagues. He has also shown that the cosmic ray climate link explains part the faint young Sun paradox, since the slowly decreasing solar wind will give rise to a cooling effect that compensates the
solar irradiance Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre ( ...
increase. Moreover, long term star formation activity in the Milky Way correlate with long term climate variations. In a more recent work with Andreas Prokoph and Ján Veizer, it was argued that the reconstructed temperature has a clear 32 million year oscillation that is consistent with the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
's motion perpendicular to the galactic plane. The oscillation also appears to have a secondary modulation consistent with the radial epicyclic motion of the Solar System.


Solar variation and climate sensitivity

Because the existence of a significant cosmic ray climate link implies that solar variability will also have a large effect on the climate, Shaviv advocated the idea that natural climate variations play a significant role in 20th century climate change. Moreover, if solar activity increase over the 20th century contributed to warming in addition to the anthropogenic forcing, then the overall climate sensitivity should be lower than advocated by standard scenarios which do not include solar forcing. In 2008, Shaviv used the oceans as a giant
calorimeter A calorimeter is a device used for calorimetry, or the process of measuring the heat of chemical reactions or physical changes as well as heat capacity. Differential scanning calorimeters, isothermal micro calorimeters, titration calorimeters ...
to quantify the solar radiative forcing. He found that the peak to peak variations are close to 1 W/m2, significantly more than can be expected from the changes in the solar irradiance. In 2011, he published a paper with Shlomi Ziskin arguing that the solar variability explains about half the 20th century warming, with the other half attributable to anthropogenic forcing. Shaviv's solar hypothesis has been disputed by Mike Lockwood and Claus Froehlich (1936–2019) 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 Sunspots are temporary spots on the Sun's surface that are darker than the surrounding area. They are one of the most recognizable Solar phenomena and despite the fact that they are mostly visible in the solar photosphere they usually aff ...
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 Lag, or similar, may refer to: Lag * Łąg, Poland * Lag (company), a French guitar maker * Lag (cue sports), a brief pre-game competition to determine which player will go first * Latency (engineering), a slower response time in computing, co ...
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. Later quantitative modeling showed that indeed there is no discrepancy. The perceived "
hiatus Hiatus may refer to: * Hiatus (anatomy), a natural fissure in a structure * Hiatus (stratigraphy), a discontinuity in the age of strata in stratigraphy *''Hiatus'', a genus of picture-winged flies with sole member species '' Hiatus fulvipes'' * G ...
" in the early 2000s is a natural consequence of the decreased
solar activity Solar phenomena are natural phenomena which occur within the Stellar atmosphere, atmosphere of the Sun. They take many forms, including solar wind, Solar radio emission, radio wave flux, solar flares, coronal mass ejections, Stellar corona#Coron ...
.


Rejection of human-caused climate change

Shaviv disagrees with the scientific consensus on human-caused climate change.Nir Shaviv
Desmogblog. Retrieved 12/07/2018.
He claims that solar activity changes have contributed between half to two thirds of the warming over the 20th century, and that
climate sensitivity Climate sensitivity is a key measure in climate science and describes how much Earth's surface will warm for a doubling in the atmospheric carbon dioxide () concentration. Its formal definition is: "The change in the surface temperature in resp ...
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 doubling. Shaviv was interviewed for ''
The Great Global Warming Swindle ''The Great Global Warming Swindle'' is a 2007 British polemical documentary film directed by Martin Durkin (director), Martin Durkin. The film Climate change denial, denies the Scientific consensus on climate change, scientific consensus about ...
'' documentary. In the film he states: In 2012, he contributed, along with Werner Weber,
Henrik Svensmark Henrik Svensmark (born 1958) is a Danish physicist and professor in the Division of Solar System Physics at the Danish National Space Institute (DTU Space) in Copenhagen. He is known for his work on the hypothesis that fewer cosmic rays are an in ...
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 Climate change denial (also global warming denial) is a form of science denial characterized by rejecting, refusing to acknowledge, disputing, or fighting the scientific consensus on climate change. Those promoting denial commonly use rhetor ...
, which attracted considerable interest in Germany. Numerous scientists criticised the book and considered its underlying assumptions to be either outdated or highly speculative. In 2018, the German Bundestag's environment committee invited him as an expert to the
German Parliament The Bundestag (, "Federal Diet") is the lower house of the German federal parliament. It is the only constitutional body of the federation directly elected by the German people. The Bundestag was established by Title III of the Basic Law for ...
. There he denied that carbon dioxide had a substantial effect on climate changeKlimawandel durch kosmische Strahlung? Klimawandel-Leugner im parlamentarischen Alltag
ARD Monitor. Retrieved 12/07/2018
and claimed the
Intergovernmental Panel on Climate Change The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations. Its job is to "provide governments at all levels with scientific information that they can use to develop climate policies". The World Met ...
(IPCC) was ignoring information that the sun was the primary cause for climate change. Nir Shaviv has been a speaker for
the Heartland Institute The Heartland Institute is an American conservative and libertarian 501(c)(3) nonprofit public policy think tank known for its rejection of both the scientific consensus on climate change and the negative health impacts of smoking. Founded ...
.


Prizes and awards

* 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 The Institute for Advanced Study (IAS) is an independent center for theoretical research and intellectual inquiry located in Princeton, New Jersey. It has served as the academic home of internationally preeminent scholars, including Albert Ein ...
, Princeton


Selected papers

* * * * * * * *


Lectures (selection)

* (invited)


References


External links


Sciencebits.com
Shaviv's weblog * Shaviv'
home page
at the Hebrew University {{DEFAULTSORT:Shaviv, Nir Living people Israeli scientists 1972 births American climatologists Scientists from Ithaca, New York Academic staff of the Hebrew University of Jerusalem Israeli astrophysicists American emigrants to Israel Jewish American physicists Unit 8200 alumni