He is the past head of the Geological Museum at the University of Oslo (a position he held for 12 years) and the past head of the Natural History Museums and Botanical Garden of the University of Oslo.
Speaking at the 2nd International Conference on Climate Change hosted by the conservative think tank Heartland Institute on March 8, 2009, Segalstad discussed ice core samples used to explain climate change, saying that he believed there were a multitude of errors made in their collection, which "contaminated" the results. He also stated that the "composition of ocean water...can act as a buffering agent in the alleged acidification of the oceans".
Segalstad was a reviewer of the IPCC Third Assessment Report, acting as one out of sixteen reviewers from Norway in the Working Group 1 of the IPCC  but disagreed with the mainstream scientific view of global warming from the assessment. He believes that human-released carbon dioxide (CO2) won't have a large effect on the Earth's climate, claiming that it produces only a small percent of the greenhouse effect, and that most CO2 would be absorbed by the ocean through geological processes. According to his own account, after the results of the assessment were published, he resigned from the IPCC.
He explained later in regards to the report that the summary of the report had been released first, which attracted a large amount of media attention. He then claimed that the leader of the team making the IPCC report then stated that the information in the report had to match what had been stated in the summary, even though the summary had been written by government representatives and members of environmental organizations, not by scientists in the field of study.
Researchers Richard Bellerby, Are Olsen, and Gisle Nondal wrote a series of articles in Norwegian newspaper Forskning about Segalstad's stated beliefs and research on human CO2 emissions and how they do not affect climate change. The researchers went through Segalstad's points and gave counterarguments, concluding that he had used "incorrect interpretations of laws and geochemical data, in addition to a complete neglect of published measurements". They also repeatedly mentioned that Segalstad has yet to publish his CO2 research in any "recognized scientific journal".
- List of scientists opposing the mainstream scientific assessment of global warming
- Global warming controversy
- Tom V. Segalstad (October 25, 2010). "Biography of Tom Victor Segalstad". University of Oslo. Retrieved October 30, 2011.
- Tom Victor Segalstad, Natural History Museum of the University of Oslo, May 31, 2011
- International Geological Congress (August 6–14, 2008). "Metallogeny of the Arctic Region" (PDF). Retrieved October 30, 2011.
- Marc Sheppard (March 15, 2009). "The Clear and Cohesive Message of the International Conference on Climate Change". American Thinker. Retrieved October 30, 2011.
- Dan Miller; Daniel Foty; Thomas Sheahen (May 1, 2009). "Climate Conference Keynoters Rebuke Alarmists". Heartlander. Retrieved October 29, 2011.
- "Appendix IV – Reviewers of the IPCC WGI Third Assessment Report", Working Group I: The Scientific Basis, IPCC, 2001
- Lawrence Solomon. "Models trump measurements". Financial Post. Archived from the original on October 23, 2011. Retrieved October 30, 2011.
- Ellen Kongsnes (February 20, 2010). "En kald vinter er ikke avgjørende". Stavanger Aftenblad (in Norwegian). Retrieved October 30, 2011.
- Inge Berge (March 31, 2008). "En politisk miljøbløff". NA24 (in Norwegian). Retrieved October 30, 2011.
- NTB (April 5, 2008). "Stoltenbergs ekspert er reveforsker". Hegnar Online (in Norwegian). Retrieved October 30, 2011.
- Øystein Sjølie (July 1, 2008). "Hudfletter FNs klimapanel". E24 Næringsliv (in Norwegian). Retrieved October 30, 2011.
- Bellerby, Richard; Olsen, Are; Nondal, Gisle (August 12, 2008). "CO2-økningen er ikke naturlig". Forskning (in Norwegian). Retrieved October 30, 2011.
- Bellerby, Richard; Olsen, Are; Nondal, Gisle (May 7, 2008). "Atmosfærens CO2-økning er menneskeskapt". Forskning (in Norwegian). Retrieved October 30, 2011.
- Tom Segalstad's web site
- Tom V. Segalstad (July 31, 2011). "Web-info about CO2 and the "Greenhouse Effect" Doom by Tom V. Segalstad". University of Oslo. Retrieved October 30, 2011.