The head of the British research unit at the center of a controversy over the disclosure of thousands of e-mail messages among climate-change scientists has stepped down pending the outcome of an investigation. Phil Jones, the director of the Climatic Research Unit at the University of East Anglia in England, said that he would leave his post while the university conducted a review of the release of the e-mail messages. The university has called the release and publication of the messages a 'criminal breach' of the school's computer systems. The e-mail exchanges among several prominent American and British climate-change scientists appear to reveal efforts to keep the work of skeptical scientists out of major journals and the possible hoarding and manipulation of data to overstate the case for human-caused climate change. In a related announcement, Pennsylvania State University said it would review the work of a faculty member who is cited prominently in the e-mail messages, Michael Mann, to assure that it meets proper academic standards. Skeptics have seized upon the disclosures to call into question years of efforts to document changes to the climate and its causes. Republicans in Congress have begun an investigation into the work of the scientists who sent the messages -- many of whom have conducted much of their research with money from the federal government -- and the scientific and policy decisions that may have flowed from them. The British university has contended that the messages were illegally obtained by a hacker, who posted them on Web sites of groups critical of the current scientific consensus that human activity has caused dangerous changes to the global climate. Jones, in a statement issued by the climate research unit, said, 'What is most important is that CRU continues its world-leading research with as little interruption and diversion as possible.' He added that 'the best way to achieve this is by stepping aside from the director's role during the course of the independent review.' For more than a week, the episode has fueled a fierce debate on the blogosphere and in newspaper opinion columns and once again placed global warming science under intense scrutiny. Sen. James M. Inhofe, R-Okla., who is the most outspoken climate-change skeptic in Congress, renewed his call for an investigation on Tuesday. 'The e-mails reveal possible deceitful manipulation of important data and research,' Inhofe wrote. 