Image caption There is debate over "feedback" effects on the climate

The UK's Royal Society is reviewing its public statements on climate change after 43 Fellows complained that it had oversimplified its messages.

They said the communications did not properly distinguish between what was widely agreed on climate science and what is not fully understood.

The society's ruling council has responded by setting up a panel to produce a consensus document.

The panel should report in July and the report is to be published in September.

It is chaired by physicist John Pethica, vice-president of the Royal Society.

Its deliberations are reviewed by two critical sub-groups, each believed to comprise seven members.

Each of these groups contains a number of society Fellows who are doubtful in some way about the received view of the risks of rising CO2 levels.

It's not clear to me how we are going to get precise agreement on the wording Review member

One panel member told me: "The timetable is very tough - one draft has already been rejected as completely inadequate."

The review member said it might not be possible for the document to be agreed at all. "This is a very serious challenge to the way the society operates," I was told. "In the past we have been able to give advice to governments as a society without having to seek consensus of all the members.

"There is very clear evidence that governments are right to be very worried about climate change. But in any society like this there will inevitably be people who disagree about anything - and my fear is that the society may become paralysed on this issue."

Another review member told me: "The sceptics have been very strident and well-organised. It's not clear to me how we are going to get precise agreement on the wording - we are scientists and we're being asked to do a job of public communication that is more like journalism."

But both members said they agreed that some of the previous communications of the organisation in the past were poorly judged.

Question everything

A Royal Society pamphlet Climate Change Controversies is the main focus of the criticism. A version of it is on the organisation's website. It was written in response to attacks on mainstream science which the Royal Society considered scurrilous.

It reads: "This is not intended to provide exhaustive answers to every contentious argument that has been put forward by those who seek to distort and undermine the science of climate change…"

One Fellow who said he was not absolutely convinced of the dangers of CO2 told me: "This appears to suggest that anyone who questions climate science is malicious. But in science everything is there to be questioned - that should be the very essence of the Royal Society. Some of us were very upset about that.

"I can understand why this has happened - there is so much politically and economically riding on climate science that the society would find it very hard to say 'well, we are still fairly sure that greenhouse gases are changing the climate' but the politicians simply wouldn't accept that level of honest doubt."

Another society protester said he wanted to be called a climate agnostic rather than a sceptic. He said he wanted the society's website to "do more to question the accuracy of the science on climate feedbacks" (in which a warming world is believed to make itself warmer still through natural processes).

"We sent an e-mail round our friends, mainly in physical sciences," he said.

"Then when we had got 43 names we approached the council in January asking for the website entry on climate to be re-written. I don't think they were very pleased. I don't think this sort of thing has been done before in the history of the society.

"But we won the day, and the work is underway to re-write it. I am very hopeful that we will find a form of words on which we can agree.

"I know it looks like a tiny fraction of the total membership (1,314) but remember we only emailed our friends - we didn't raise a general petition."

Precautionary principle

He said the agnostics were also demanding a "more even-handed" bibliography.

The first "climate agnostic" also said he was angry at previous comments from the previous president Lord May who declared: "The debate on climate change is over."

Lord May was once quoted as saying: "'On one hand, you have the entire scientific community and on the other you have a handful of people, half of them crackpots."

One source strongly criticised the remarks.

Lord May's comments were made at a time when world scientists were reaching a consensus (not unanimity) that CO2 had warmed the planet and would probably warm it more - maybe dangerously so.

Lobbyists funded by the fossil fuel industry were fighting to undermine that consensus and science academies were concerned that public doubt might deter governments from taking precautionary action to reduce emissions of CO2.

Climate change doubters among the society's Fellows say that in their anxiety to support government action, the academies failed to distinguish between "hired guns" and genuine scientific agnostics wanting to explore other potential causes of climate change.

The remit of the society panel is to produce a new public-facing document on what scientists know, what they think they know and which aspects they do not fully understand. The task is to make the document strong and robust.

It should answer the complaint that previous communications have failed to properly explain uncertainties in climate science.

Language of risk

At the Heartland Institute climate sceptics conference in Chicago, Richard Lindzen, professor of meteorology at Massachusetts Institute of Technology (MIT), criticised the current society president Lord Rees for what he described as exaggerating the certainty in a joint public letter with Ralph Cicerone, president of the US National Academy of Sciences.

The letter, published by the Financial Times newspaper, states: "Something unprecedented is now happening. The concentration of carbon dioxide in the atmosphere is rising and climate change is occurring, both due to human actions…. Uncertainties in the future rate of (temperature) rise, stemming largely from the 'feedback' effects on water vapour and clouds, are topics of current research."

Professor Lindzen says the "unprecedented" statement is misleading because neither the current warming nor the CO2 level are unprecedented. He complains that the statement on uncertainties is also misleading because it does not reveal that uncertainties about future climate projections are, in his view, immense.

A spokesman for the society defended the letter, saying that the rise in man-made CO2 was indeed unprecedented. But Professor Lindzen told me: "This is part of an inflation of a scientific position which has sadly become rather routine for spokesmen for scientific bodies."

The forthcoming Royal Society publication - if it can be agreed by the review panel - will be scrutinised closely because the society carries huge weight in global science. Under Lord May it was prime mover of a joint letter of international academies stating that climate change was a major concern.

The comments from the current president Lord Rees in his first Reith lecture next week are rather carefully measured and couched in the language of risk rather than certainty - but even in this speech, critics are likely to say that in some particulars he does not sufficiently distinguish between what is certain and what is very widely believed.