An Oxford academic has won the right to read previously secret data on climate change held by the University of East Anglia (UEA). The decision, by the government's information commissioner, Christopher Graham, is being hailed as a landmark ruling that will mean that thousands of British researchers are required to share their data with the public.

The ruling also marks a victory for critics of the UEA and its Climatic Research Unit in the "climategate" affair. It comes at the end of a two-year rearguard action by UEA climate scientists to prevent publication of their "crown jewels", an archive of world temperature records collected jointly with the Met Office.

Jonathan Jones, physics professor at Oxford University and self-confessed "climate change agnostic", used freedom of information law to demand the data that is the life's work of the head of the University of East Anglia's Climatic Research Unit, Phil Jones. UEA resisted the requests to disclose the data, but this week it was compelled to do so.

Graham gave the UEA one month to deliver the data, which includes more than 4m individual thermometer readings taken from 4,000 weather stations over the past 160 years. The commissioner's office said this was his first ruling on demands for climate data made in the wake of the climategate affair.

Critics of the UEA's scientists say an independent analysis of the temperature data may reveal that Phil Jones and his colleagues have misinterpreted the evidence of global warming. They may have failed to allow for local temperature influences, such as the growth of cities close to many of the thermometers.

But Jonathan Jones, who is not a climate scientist, said he thought "the most significant features of this decision are the precedents that have been set". The commissioner is likely to rule more generally in favour of public access to scientific data.

Under the 2000 Freedom of Information Act, public bodies such as universities have to share their data unless there are good reasons not to. But when Jonathan Jones and others asked for the data in the summer of 2009, the UEA said legal exemptions applied. It said variously that the temperature data were the property of foreign meteorological offices; were intellectual property that might be valuable if sold to other researchers; and were in any case often publicly available.

But in a damning verdict, Graham said suggestions that international relations could be upset by disclosure were "highly speculative", and "it is not clear how UEA might have planned to commercially exploit the information requested."

Jonathan Jones said this week that he took up the cause of data freedom after Steve McIntyre, a Canadian mathematician, had requests for the data turned down. He thought this was an unreasonable response when Phil Jones had already shared the data with academic collaborators, including Prof Peter Webster of the Georgia Institute of Technology in the US. He asked to be given the data already sent to Webster, and was also turned down. So he appealed to the information commissioner.

"I am extremely concerned about the apparent pattern of secrecy and evasion," he said. "My sole aim [in pursuing the case] is to help restore climate science to something more closely resembling scientific norms."

The UEA said: "We have nothing to fear from scrutiny; we are committed to openness and transparency in our research... and we fully intend to make all data publicly available as soon as possible."