Two of the scientists involved in "Climategate" – the e-mail hacking incident at the Climatic Research Unit (CRU) of the University of East Anglia, UK – have been emailed death threats since the contents of their private e-mails were leaked to the world. No further information can be revealed about these particular threats at present because they are currently under investigation with the FBI in the United States.

Many other CRU scientists and their colleagues have received torrents of abusive and threatening e-mails since the leaks first began in mid-November 2009. Tom Wigley, previous Director of CRU and now at the National Center for Atmospheric Research (NCAR), Boulder, US, has been horrified by the e-mails he and other colleagues have received. "They are truly stomach-turning and show what sort of venomous monsters we are up against," he told environmentalresearchweb.

The scandal, dubbed "Climategate", broke on 19 November this year when hundreds of messages between scientists from CRU and their colleagues around the world were posted onto websites. Since then, segments of the messages have been used by climate-change sceptics to undermine the scientific case for climate change being caused by humanity's greenhouse-gas emissions.

In the UK a police investigation is underway to uncover how the material was hacked or leaked. Meanwhile, the University of East Anglia has ordered an independent review into the allegations against CRU and Phil Jones has temporarily stepped down as director of CRU, until the investigations are completed.

Many of the accusations being made by climate-change sceptics are based on fragments and selected phrases from e-mails sent by eminent climate scientists, dating back to 1996. The scientists involved are confident that they can counter all of the claims against them. "None of it affects the science one iota," said Wigley. "Accusations of data distortion or faking are baseless. I can rebut and explain all of the apparently incriminating e-mails that I have looked at, but it is going to be very time consuming to do so."

In particular Wigley vigorously denies that any data was ever destroyed. "We did not destroy any primary records," he said. "All these data came from National Meteorological Services, and the originals are still there for anyone to access. Indeed other groups such as GISS and NOAA have independently accessed these data and independently reproduced our results."

Climate scientists not caught up in the scandal agree that the independent investigation is necessary, but don't believe that the CRU science will be discredited or any misdoings uncovered. "CRU is just one of many climate-research institutes that provide the underlying scientific basis for climate policy at national and international levels," said Dave Reay, a climate scientist at the University of Edinburgh, UK. "The conspiracy theorists may be having a field day, but if they really knew academia they would also know that every published paper and data set is continually put through the wringer by other independent research groups. The information that makes it into the IPCC reports is some of the most rigorously tested and debated in any area of science."

And some scientists express little surprise at the tactics being used to try and undermine the science. "We have always had a very vocal minority of people who have long since decided to ignore the science and the data and take a deliberately and completely contrarian view, and who have always and constantly accused (all) climate scientists of falsehood and being in it for the money," said Andy Ridgwell, a climate scientist at the University of Bristol. "They have been playing Chicken Little and claiming the sky is falling in on climate science for a decade. There is nothing left that is new or different that they can (falsely) claim or accuse us of."

Nonetheless there are now concerns that the e-mail leaks could derail some of the objectives due to be set at the UN climate summit in Copenhagen, Denmark, next week. On Friday 4 December Saudi Arabia's lead climate negotiator, Mohammad Al-Sabban, told BBC news that the hacked e-mails suggest climate change does not have a human cause, and that he thought it could have a huge impact on agreeing limitations of greenhouse gases at the summit. Meanwhile, Rajendra Pachauri, head of the Intergovernmental Panel on Climate Change (IPCC), was reported by the BBC as saying that the claims were serious and needed to be investigated.

For now the scientists involved in the scandal are anxious to get back to doing their research. "We must continue to do the science," said Wigley. "As time goes by the evidence mounts – it is already overwhelming – and we must continue to report this through normal channels in peer-reviewed scientific journals. We must continue to strive to understand the complexities of the climate system better and to improve climate models so that we better know how to respond to future climate changes."

But Wigley fears that time may be running out. "As time goes by, however, we are approaching the point where any actions we might take will be inadequate to protect humanity and the planet from dangerous climate change," he said. "Those people – the hackers, the sceptics, the luddite bloggers – who are hindering and slowing down the process of response will, I hope, eventually be held accountable. They already have much to answer for."