Two weeks ago, the United States National Academy of Sciences published its clearest ever report on the science of climate change. It concluded: "Climate change is occurring, is caused largely by human activities, and poses significant risks for a broad range of human and natural systems."

Over recent years, particularly during the George W Bush administration, the academy has faced great challenges in presenting the science of climate change to domestic policymakers, many of whom have been in denial about the consequences of greenhouse gas emissions.

But with Barack Obama in the White House, the academy has been more able to offer scientific advice that some politicians may find inconvenient.

So it is ironic that just as the leading scientists in the US give their clearest warning about climate change, we now see suggestions that some fellows of UK's national academy of science, the Royal Society, might be disputing the evidence.

Last December, ahead of the United Nations conference in Copenhagen, the society published a statement entitled Preventing dangerous climate change, which was unequivocal.

It said: "It is certain that GHG [greenhouse gas] emissions from the burning of fossil fuels and from land use change lead to a warming of climate, and it is very likely that these GHGs are the dominant cause of the global warming that has been taking place over the last 50 years."

But now, 43 of the society's 1,489 fellows have written to complain about some of its statements about climate change published over the last few years. It is not clear exactly what the 43 have concerns about.

And because their identities have not been made public, we do not know whether any of them are climate researchers.

There are certainly some fellows working outside climate science who dispute the findings of mainstream researchers.

One such is Anthony Kelly, a member of the academic advisory council of the Global Warming Policy Foundation, a lobby group set up by Nigel Lawson last year to promote scepticism about climate change.

Professor Kelly is an 81-year-old distinguished research fellow in materials science and metallurgy at Cambridge University.

The other members of the GWPF's academic advisory council include Ian Plimer, the Australian geologist who has wrongly claimed that volcanoes produce more carbon dioxide than human activities.

The news that 43 fellows apparently disagree with the society is likely to generate even further public confusion about the causes and consequences of climate change.

A YouGov poll published earlier this week found that 40% of the public either do not believe climate change is happening, or think scientists are divided about its occurrence, compared with 32% last year.

The Royal Society is carrying out a review of its statements on climate change in response to the fellows' letter. It will no doubt prefer to remain silent until the review is completed.

But given the impact of the controversies over the University of East Anglia's Climatic Research Unit and the Intergovernmental Panel on Climate Change, it would be better if the 43 fellows made their concerns public, and the society clarified where it stands on the scientific evidence about climate change.

• Bob Ward is policy and communications director at the Grantham Research Institute on Climate Change and the Environment at the London School of Economics and Political Science, and was head of media relations at the Royal Society until September 2006.