Klaus-Eckart Puls is a German physicist and meteorologist. He initially accepted the "science" coming from the IPCC. But was ashamed that he made presentations without first checking it.
Here is Klaus-Eckart Pulsin an interview with Swiss Magazine "factum" and reported by EIKE - the European Institute for Climate and Energy (link)
factum: Sie kritisieren seit Jahren die Theorie vom menschengemachten Klimawandel. Inzwischen melden sich viele prominente Wissenschaftler in diesem Sinn zu Wort. Wie wurden Sie zum Klimaskeptiker?
Ten years ago I simply parroted what the IPCC told us. One day I started checking the facts and data – first I started with a sense of doubt but then I became outraged when I discovered that much of what the IPCC and the media were telling us was sheer nonsense and was not even supported by any scientific facts and measurements. To this day I still feel shame that as a scientist I made presentations of their science without first checking it.
Read the whole piece but note Klaus-Eckart Puls' concluding sentences: