Dipl.-Ing. Peter Dietze from Langensendelbach (Germany) near Nuremberg (Nürnberg) is an energy and climate consultant. He was an official scientific IPCC TAR (Intergovernmental Panel on Climate Change; Third Assessment Report) Reviewer.
Dietze is not a climate scientist
Deitze is an electrical engineer. According to a search of 22,000 academic journals, Dietze has not published any research in a peer-reviewed journal on the subject of climate change. There is a "P.Dietze" listed in three research papers from the 1970's on electrical engineering. 
Dietze and the "Leipzig Petition"
Deitze was a signatory  to the 1995 "Leipzig Declaration", a project of Fred Singer's  Science and Environmental Policy Project and a group called the European Academy of Environmental Affairs. The Declaration stated that: "there does not exist today a general scientific consensus about the importance of greenhouse warming from rising levels of carbon dioxide."
When a Danish journalist attempted to contact the 33 European scientists listed on the petition, 12 denied signing the petition and some had not even heard of the Leipzig Declaration. Of those that did admit signing the letter, one was a doctor and another was an expert in flying insects. The Declaration was then revised and Dietze's name, among others, was removed. 
It is interesting to note that a similar tactic was used in the Oregon Institute petition.  Fred Singer and his organization and the George C. Marshall Institute were also heavily involved in the Oregon Petition.
- DeSmogBlog's research on Dietze.
- Peter Dietze, "Little Warming with new Global Carbon Cycle Model," August 11, 1997.
- Peter Dietze, "Estimation of the solar fraction and Svensmark factor," July 9, 1999.
- Peter Dietze, "IPCC's Most Essential Model Errors," June 1, 2000.
- Peter Dietze, "Carbon Model Calculations," February 2001.