According to this, a laborious gathered archive of global temperature has been lost. Apparently some Brits, with US government funding gathered up temperature readings from all over the world going back to the invention of the thermometer. The project has refused to show their raw data to other scientists for years. Now as Freedom of Information Act queries have demanded to see their data, they claim to have lost it.
The matter is more than academic. The IPCC used this data to claim the world was getting hotter. Despite a good deal of correction of the data to account for the rise of well heated cities around the older weather stations, the IPCC was only able to claim a warming of a fraction of a degree. Thermometers are only accurate to two degrees, so the amount of warming is so small that thermometers can't really see it. The IPCC warming was detected only after a lot of statistical averaging on corrected data. There are lies, damn lies, and statistics Mark Twain once said. A fraction of a degree of warming might come from the statistics or the corrections, or both.
Naturally other scientists want to check the numbers. And the global warmers don't want to let them see the data that was used sell the Cap and Tax bill to the US Congress.