He admitted that he based his claim on discredited data:
"A letter he published on 16 April 2005 in
New Scientist asserted that a large proportion (555 of 625) of the glaciers being observed by the
World Glacier Monitoring Service were advancing, not retreating.
[21] George Monbiot of
The Guardian tracked down Bellamy's original source for this information and found that it was from
discredited data originally published by Fred Singer, who claimed to have obtained these figures from a 1989 article in the journal
Science: however, Monbiot proved that this article had never existed.
[22] Bellamy subsequently accepted that his figures on glaciers were wrong, and announced in a letter to
The Sunday Times in 2005 that he had "decided to draw back from the debate on global warming",
[23] although Bellamy jointly authored a paper with Jack Barrett in the refereed
Civil Engineering journal of the
Institution of Civil Engineers, entitled "Climate stability: an inconvenient proof" in May 2007.
[24]"
David Bellamy - Wikipedia
It comes down not to bias or unbias in scientists, but if their claims appear accurate with given data. Unfortunately, climate change appears to be a real problem.