Norfolk Police announced the shutdown of a 2 1/2-year investigation into the breach at the University of East Anglia's Climatic Research Unit, The Guardian reported.
Detective Chief Superintendent Julian Gregory said there is no "realistic prospect" of identifying suspects and bringing charges within legal time limits.
"However, as a result of our inquiries, we can say that the data breach was the result of a sophisticated and carefully orchestrated attack on the CRU's data files, carried out remotely via the internet. The offenders used methods common in unlawful Internet activity to obstruct inquiries," he said. "There is no evidence to suggest that anyone working at or associated with the University of East Anglia was involved in the crime."
Thousands of e-mails to and from the climate research unit were published in 2009, and more were published last year.
Climate change skeptics seized on some of the communications as evidence that scientists were tweaking the data or worse, but several investigations have found no credible evidence of scientific fraud.