Giaever has repeatedly professed skepticism of global warming, calling it a "new religion."[10][11][11][12]
In a featured story in Norway's largest newspaper, Aftenposten, 26 June 2011, Giaever stated, "It is amazing how stable temperature has been over the last 150 years."[13]
On 13 September 2011, Giaever resigned from the American Physical Society over its official position. The APS Fellow noted: "In the APS it is ok to discuss whether the mass of the proton changes over time and how a multi-universe behaves, but the evidence of global warming is incontrovertible?"[14]
As part of the 62nd Lindau Nobel Laureate Meeting, Giaever commented on the significance of the apparent rise in temperature when he stated, "What does it mean that the temperature has gone up 0.8 degrees Kelvin: probably nothing." Referring to the selection of evidence in his presentation, Giaever stated "I pick and choose when I give this talk just the way the previous speaker (Mario Molina) picked and chose when he gave his talk." Giaever concluded his presentation with a pronouncement: "Is climate change pseudoscience? If I’m going to answer the question, the answer is: absolutely."[15][16]
Giaever repeated his claims in a speech at the same place in 2015,[17] referring to data on global average temperature (GISTEMP) published amongst others by NASA[18] that show global average surface temperature has risen less than 1K in 140 years,[19] and not risen at all for the years from 2000 - 2014.[20]
A main point of his speech was discussing reliability of the statistical calculation of this temperature with respect to the quite inhomogeneousspatial distribution of measurement locations over the globe, especially the poor coverage in the southern hemisphere.[21] He highlighted the fact evident from the dataset used by NASA for the calculations that there have been only 8 measurement locations on the entire Antarctic continent, which holds the greatest and currently further increasing mass of ice found on earth. He claimed that these facts erode the credibility of accuracy usually attached to these data, notwithstanding that established statistical procedures have been used to cope with that lack of data statistical independence and hence data quality.
Another main point was that observed significant change in atmospheric carbon dioxide (CO2) concentrations in a magnitude of 40% during the last 250 years of the industrial age[22] does in no way correlate with the observed temperature change[23] in that time, thus experimentally rendering invalid the claim that rising concentrations of CO2 are the cause of global warming, as stated by the UN led Intergovernmental Panel on Climate Change (IPCC) and leading climatologists from different countries in a vast amount of publications, and widely believed as a fact in scientific as well as political discussions worldwide.
Giaever is currently a science advisor with The Heartland Institute.[24]