Global environmental research could be seriously damaged in an escalating dispute about who should pay for satellite data.

Last week the United States fired the latest salvoes in what is being called a potential "data war".

It threatened to restrict European researchers' access to its weather data, including data from its polar satellites, the only satellites that provide temperature and moisture measurements around the whole globe.

A data war would send re-searchers' costs up. But the biggest worry, said Francis Bretherton, of the University of Wisconsin, author of an influential report on open exchange of environmental information, is that the long-term climate record will falter.

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"It's rubbish to pretend that because the raw data is still being collected it can be processed much later. Quality control needs to be done immediately," he said.

The underlying problem is that many governments are abandoning their century-old commitment to free provision of international weather data, said Elbert Friday, director of the US national weather service. The US, however, is committed to making its data fully available to the private sector in the US at marginal cost.

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Dr Friday told the American Association for the Advancement of Science: "There is a conflict. The private sector, which has readily available data from the US and other countries which carry out free and unrestricted policies is in conflict with the public sector in other countries which, as part of their mandate from their governments, must obtain some of their costs by sales. This has created some difficulties."

The World Meteorological Organisation agreed a policy on the problem last year, including the commitment that no restrictions should be placed on access to data for non-commercial research. Dr Friday is now objecting to the latest European interpretation of this policy.

"The western European directors of meteorological offices now say that those data are not to be used on the Internet or any other non-restricted data source.

"We never agreed to that. Furthermore, they say that the research community should be required to sign a formal document before being allowed to use any of the data. That's far beyond anything we agreed to."

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He complained that data from Eumetsat, the European body that runs weather satellites data, "is now encrypted and the only information available for general use is six-hourly data. If you want anything beyond that you have to enter special licensing at a substantial cost. I am now being asked to retaliate".

Dr Friday added: "Restrictions on data could generate a data war and all that is going to do is harm everyone.

"We may have to stop our free exchange of data with those nations which place those restrictions on us. Then restrictions would apply, including restrictions on the US polar orbiter data."