Logs, that is, not blogs. Researchers in the UK are studying climate change as recorded in ships logs of the British, Dutch and Spanish navies. Even though the records pre-date common use of scientific instruments,

Dr Wheeler told BBC News Online, "We've verified that the data are highly reliable. You find lots of ships sailing in convoy, and they all record the same thing. There's a remarkable consistency of observation. And remember, the crews' lives depended on them getting their records right.