LONDON -- Police in eastern England have closed a two-and-a-half-year investigation into the 2009 "Climategate" email thefts without identifying any suspects but exonerating the staff at the targeted University of East Anglia's Climatic Research Unit (CRU).

The online theft and subsequent double release of thousands of carefully selected documents, emails and files relating to the unit's work put fire into the belly of the climate skeptic lobby and triggered death threats to CRU leader Phil Jones and his staff.

"Looking at the overall status of the investigation, and in view of the imminent three-year deadline under the Computer Misuse Act, we concluded there was no realistic prospect of mounting a prosecution in that time scale, so we decided to conclude," said Detective Chief Superintendent Julian Gregory, the senior investigating officer.

"We did investigate the staff at the UEA in the Climatic Research Unit. We didn't find anything which supported that anybody was involved. With what I know about the way the attack was conducted, the level of sophistication involved, my personal view is that it is very unlikely that it was anyone from the UEA," he said by telephone from Norfolk police headquarters in Wymondham about 110 miles northeast of London.

Gregory said the attacker or attackers used a series of proxy servers as cutoffs in a network that crisscrossed the globe to remotely hack into a backup server in the CRU between September and November 2009 when the first batch was released on the Internet just ahead of the U.N. climate summit in Copenhagen, Denmark. The second batch was published two years later just before the U.N. climate conference in Durban, South Africa.

The emails purported to show that the CRU scientists had tried to manipulate, twist or bury data that did not support the theory of human-induced climate change.

"The data, the emails in particular, were selectively taken and portrayed in a way which appears to have been intended to undermine the scientists and therefore the validity of their science, and it was published on the Internet in the run-up to two major climate change conferences," Gregory said.

"The conclusion you are led to is that it was done with the intention of influencing the outcome of those conferences," he added.

Not only did the theft fuel the flagging skeptic lobby, but it raised serious questions about climate science among the general public in view of the high-level finger-pointing that followed the virtual collapse of the Copenhagen meeting.

But a total of eight inquiries on both sides of the Atlantic Ocean have since cleared the climate scientists of wrongdoing and endorsed their findings that climate change is happening and exacerbated by human activities -- although at least one criticized a lack of transparency in their workings.

Activists say skeptics will be 'defeated' by science

Gregory said the UEA had, as a result of the hacking, changed its computer security protocols, and he expected that other institutions would probably have done likewise, but he said there inevitably would be a downside.

"The universities are academic institutions that exist for research. Part of that ethos is about being open and accessible and facilitating that kind of activity. Having to make access more difficult for security reasons presents something of a conundrum," he said.

During the 30-month investigation, which cost nearly £85,000 ($134,000) in overtime and expenses, Gregory was bombarded with 25 requests for information under the United Kingdom's Freedom of Information Act. These requests, all of which must be answered, included how many climate skeptic books had been bought, details of train trips taken, a breakdown of monthly costs and how many death threats had been received by CRU staff.

"It is unusual. Investigations don't normally attract that level of interest or Freedom of Information requests. But that is a route that the climate skeptic community typically seem to follow. UEA had been inundated with requests in the summer of 2009 in what had the appearance of an orchestrated campaign," Gregory said.

Yesterday on both sides of the Atlantic, climate change proponents welcomed the Norfolk police findings but lamented the fact that no culprit had been found, and they urged the skeptics to stop muddying the waters.

"There is a compelling moral duty for any climate change 'sceptics' who have information about this crime to contact police immediately instead of shielding whoever is responsible from justice," Bob Ward of the London School of Economics' Grantham Research Institute on Climate Change and the Environment said in a statement.

"Climate change 'sceptics' falsely alleged that the emails revealed that scientists had been faking the evidence for climate change, but those claims have been shown to be bogus," he added.

In the United States, House Natural Resources ranking member Ed Markey (D-Mass.) said that while the skeptics continued their attacks, the science of climate change had become even more solid.

"It is only the doubters deployed by ideological zealots and fossil fuel interests who are holding back action to address climate change, and they will be defeated in time by overwhelming scientific evidence. The only question is, how soon will the deniers be exposed for their crimes against the environment?" he said.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC., 202-628-6500