A new set of climate science-related e-mails and documents has apparently been released from the Climatic Research Unit (CRU) at the University of East Anglia in Norwich, UK.

The files, including more than 5,000 e-mails of as-yet-unconfirmed authenticity, have been posted on an anonymous server in Russia.

A text file included with the released e-mails and documents seems to quote prominent researchers discussing the quality of climate reconstructions and the possibility that natural climate fluctuations might be behind the twentieth-century warming trend.

“I find myself in the strange position of being very sceptical of the quality of all present [climate] reconstructions,” one researcher is quoted as having allegedly remarked.

Another remark reads: “What if climate change appears to be just mainly a multidecadal natural fluctuation? They’ll kill us probably.”

A previous leak in 2009 of more than 1,000 CRU e-mails — quickly dubbed Climategate — had caused a long-running debate over the integrity of a group of leading climate scientists and of climate research as a whole.

British and US climate scientists, including the then-head of the CRU, Phil Jones, were subsequently cleared of any wrongdoing. But the affair did raise calls for more openness and transparency in handling and sharing climate data.

The title of the uploaded file — FOIA.zip — suggests that the e-mails released today have been taken from CRU servers by the same person, or group of persons, who were responsible for the 2009 leak.

As then, the release comes just weeks before a United Nations climate summit. The two-week-long meeting in Durban, South Africa, starts on 28 November.

The university said in a statement that it had no evidence of a recent breach of its systems. The statement continues: “If genuine, (the sheer volume of material makes it impossible to confirm at present that they are all genuine) these e-mails have the appearance of having been held back after the theft of data and e-mails in 2009 to be released at a time designed to cause maximum disruption to the imminent international climate talks.”

For a round-up of Nature‘s previous coverage of ‘Climategate’, see our news special.