Climate scientists in the US say police inaction has left them defenceless in the face of a torrent of death threats and hate mail, leaving them fearing for their lives and one to contemplate arming himself with a handgun.

The scientists say the threats have increased since the furore over leaked emails from the University of East Anglia began last November, and a sample of the hate mail sent in recent months and seen by the Guardian reveals the scale and vitriolic tone of the abuse.

The scientists revealed they have been told to "go gargle razor blades" and have been described as "Nazi climate murderers". Some emails have been sent to them without any attempt by the sender to disguise their identity. Even though the scientists have received advice from the FBI, the local police say they are not able to act due to the near-total tolerance of "freedom of speech" in the US.

The problem appears less severe in the UK but, Professor Phil Jones, the UEA scientist at the centre of the hacked email controversy, revealed in February he had been receiving two death threats a week and had contemplated suicide. "People said I should go and kill myself," he said. "They said that they knew where I lived. They were coming from all over the world." The third and final independent review into the issues raised by the hacked UEA emails is due to be published on Wednesday when Sir Muir Russell presents his panel's conclusions.

Professor Stephen Schneider, a climatologist based at Stanford University in California, whose name features in the UEA emails, says he has received "hundreds" of violently abusive emails since last November. The peak came in December during the Copenhagen climate change summit, he said, but the number has picked up again in recent days since he co-authored a scientific paper last month which showed that 97%-98% of climate scientists agree that mankind's carbon emissions are causing global temperatures to increase.

Schneider described his attackers as "cowards" and said he had observed an "immediate, noticeable rise" in emails whenever climate scientists were attacked by prominent right-wing US commentators, such as Glenn Beck and Rush Limbaugh.

"[The senders] are not courageous people," said Schneider. "Where are they getting their information from? They just listen to assertions made on blogs and rightwing talkshows. It's pathetic."

Schneider said the FBI had taken an interest earlier this year when his name appeared on a "death list" on a neo-Nazi website alongside other climate scientists with apparent Jewish ancestry. But, to date, no action has been taken.

"The effect on me has been tremendous," said Schneider. "Some of these people are mentally imbalanced. They are invariably gun-toting rightwingers. What do I do? Learn to shoot a Magnum? Wear a bullet-proof jacket? I have now had extra alarms fitted at my home and my address is unlisted. I get scared that we're now in a new Weimar republic where people are prepared to listen to what amounts to Hitlerian lies about climate scientists."

Dr Kevin Trenberth, head of the climate analysis section at the National Center for Atmospheric Research in Colorado, said he has also been receiving similar emails since last November when a private email of his was released into the public domain in which he had said: "The fact is that we can't account for the lack of warming at the moment and it is a travesty that we can't." Trenberth has gone on to repeatedly defend his email and explain its context, but says he has now sent a file of abusive emails totalling "19 pages of text at about 10pt font" to his university's security officials. He said the response of the US police had been "pathetic", but also blamed it on freedom-of-speech legislation.

Professor Michael Mann, director of the Earth System Science Center at Pennsylvania State University and leading proponent of the "Hockey Stick graph", said his experiences of hate mail were "eerily similar" to those described by Schneider. "I'm not comfortable talking about the details, especially as some of these matters remain under police investigation," he said. "What I can say is that the emails come in bursts, and do seem to be timed with high-profile attack pieces on talk radio and other fringe media outlets."

Last month, Mann told ABC News in the US that the following message was typical of the emails he has been receiving: "Six feet under with the roots is where you should be. I was hoping I would see the news that you'd committed suicide. Do it, freak." Another climate scientist, who wished to remain anonymous, said he had had a dead animal dumped on his doorstep and now travels with bodyguards.

Dr Gavin Schmidt, a climatologist at NASA's Goddard Institute for Space Studies in New York and co-author of the RealClimate website, said he had chosen to adopt a different strategy and now largely ignores the abusive emails he receives. "I learned a while ago that there is no way to prevent people who have no idea who you are, or what you think, or what you do, using your name to project their problems onto," he said. "Should I be offended and get annoyed, or should I just look upon my interlocutor with bemusement and pity?"

UK-based climatologists working outside of UEA report they have received far fewer abusive emails compared to their US counterparts. Dr Myles Allen, head of the climate dynamics group at University of Oxford's Atmospheric, Oceanic and Planetary Physics Department, said he only tends to get such emails when he writes an article in the press and that they "tend to start off 'Dear Communists, know that you will fail.'"

"I suspect part of the reason people feel they have to attack climate scientists is that politicians and environmentalists have a tendency to hide behind the science," he said. "In the run-up to Copenhagen, we often heard the phrase 'the science dictates' - that we need a 40% cut in rich-country emissions by 2020, for example - when in fact only a very specific, and politically loaded, interpretation of the science implied any such thing. If people who claim to be on the side of the science use scientists as human shields, it is hardly surprising that the scientists end up getting shot at."

Dr Peter Stott, head of climate monitoring and attribution at the Met Office's Hadley Centre, said he had had "mercifully few" abusive emails or letters compared to scientists in the US. "I do get letters and emails accusing me of being wrong and stupid, but I have received few really abusive ones. I got one accusing me of being a communist, but so far at the Met Office at least we haven't been on the receiving end of the types of hate mail the US scientists have apparently been getting. Also in Australia, I hear."