- Dr. Dipl.-Physiker (Physics). 
Horst-Joachim Lüdecke is a physicist and professor emeritus of computer science, physics and operations research at the University of Applied Sciences of the Saarland. He is now retired (PDF).  Before his position at Saarland, Lüdecke worked for the chemical industry creating numerical computer models for chemical facilities and for flow processes in pipelines and supply pipe networks. His doctoral research was in nuclear physics. 
He is listed as an “Advisory Board” member of the German skeptic organization EIKE and is also mentioned as their “Press Spokesman” or Press secretary for science and technology. He has written the book CO2 and climate change (Bouvier-Verlag) which suggests that climate change is a natural occurrence independent of man-made CO2. 
Stance on Climate Change
“It is the unprecedentedly rapid recovery of the Sun’s activity over the past 300 years – far stronger than anyone had previously suspected – that has been the chief driver of global warming in recent decades. We have very little to do with it.” 
“Climate Specialist I'm not. […] My criticism is well founded and professionally sound mix, but [I am] not a specialist in technical details of climate physics.” 
Horst-Joachim Lüdecke was a speaker (PDF) at the Eighth International Conference on Climate Change (ICCC-8)/Fifth International Conference on Climate and Energy (ICCE-5) sponsored by both the Heartland Institute and the European Institute for Climate and Energy (EIKE). Lüdecke's speech is titled “Causes for Recent Climate Changes: The Role of CO2.” 
December 3 - 4, 2010
Lüdecke presented at the Third International Energy and Climate Conference, hosted by EIKE. Video of his presentation (in German), which discussed “the influence of the sun on our climate,” is available here. His Power Point Presentation (.ppt) is available on the EIKE website. 
Presented at EIKE's Second International Conference on Climate and Energy. His speech was titled “Ist Klimaschutz in der heutigen Form sinnvoll?” or “Climate protection is useful in its present form?” 
Lüdecke released a book titled “CO2 and climate change - facts, errors, politics.” Bouvier-Verlag (2008). According to a critic, the essential theme of the book “is that the politics and the public are convinced only thanks to an 'incomparable political and journalistic campaign' of the climate impact of CO2 emissions, and that the majority of climate scientists is not behind the statements of the IPCC, because the causes of climate change, the are largely unknown, and the greenhouse effect is not understood physically.”
According to Urs Neu at the KlimaLounge, “It is a mixture of well-known skeptic allegations and conspiracy theory. It reflects the current trend in the arguments of skeptics, which says: The IPCC is a political conspiracy, and there is a strong group of 'scientists' who deny the human climate impact.” Neu points to a number of issues in the book including a “thin” list of facts in the book while “many statements are given only as an assertion without further justification or explanation.” 
Lüdecke responds to this criticism here (PDF), pointing to the Medieval Warm Period as further evidence that current climate change should be attributed to natural variations as opposed to man-made CO2. This is listed as one of the most-often cited arguments of climate skeptics by Skeptical Science. 
Some of Lüdecke's publications related to climate science have appeared in controversial journals like Energy & Environment, or have been published by skeptical organizations including the European Institute for Climate and Energy. In other cases, he has published articles largely in physics journals (See a recent Google Scholar Search). For example:
Horst-Joachim Ludecke. “Long-Term Instrumental and Reconstructed Temperature Records Contradict Anthropogenic Global Warming” (PDF) Supplemental version published in Energy & Environment, Vol. 22,
No. 6 (Sept. 2011).
- HORST-JOACHIM LÜDECKE (EIKE), RAINER LINK (EIKE), FRIEDRICH-KARL EWERT (EIKE). “HOW NATURAL IS THE RECENT CENTENNIAL WARMING? AN ANALYSIS OF 2249 SURFACE TEMPERATURE RECORDS,” nt. J. Mod. Phys. C 22, 1139 (2011). DOI: 10.1142/S0129183111016798.
“Open letter regarding 'climate change'” (PDF), Prof. aD Dr. Horst-Joachim Lüdecke. Retrieved from schmanck.de.
“Horst Joachim Luedecke: Reply to the criticism of my book 'CO2 and climate change, facts, errors, policy' (PDF), Bouvier-Verlag (2008). Retrieved from schmanck.de.
“Second International Climate Conference in Berlin on 12.04.09,” EIKE. Accessed November, 2012.
“Horst-Joachim Lüdecke: The Sun, not Man, warms the Earth,” Solar Cycle 25 Blog, October 16, 2011.
“8th International Conference on Climate Change (ICCC-8): V International Conference on Climate and Energy (ICCE-5). Hotel Bayerischer Hof, Munich, November 30 – December 1, 2012” (PDF) retrieved from eike-klima-energy.eu on November 24, 2012.
“3rd International Climate And Energy Conference, Berlin-Germany,” NoTricksZone, November 3, 2010.
Urs Neu. “Facts and Fallacies,” KlimaLounge, July 23, 2008.
“Reply to the criticism of my book 'CO 2 and climate change, facts, errors, policy, Bouvier-Verlag (2008)'” (PDF). Retrived from schmanck.de. Translated with Google.
“Advisory Board,” EIKE. Accessed November 25, 2012.