Actually lake sediments and ice cores are very accurate at determining climatic conditions at the time the layer was put down.
Or so you say. The lost squadron crash landed during WWII.. By the time it was relocated, it was necessary to tunnel down to the planes which after 50 years were buried in 250 feet of ice and snow pack with more than 250 "annual rings". Accurate my eye. By practice and dead brained assumptions, we'd have to tell the world everyone was mistaken, WWII actually happened more than 200 years in the past beyond what is recorded in history books. You'll excuse me if I have problems with the subject or the claimed result.
Yep, I'm sure they are - so accurate that Glacier Girl would be more than 250 years old by your methodology. Pretty amazing for a P-38 lightning, huh.. Oh, there was at least one B-17 in that grouping as well. Do you suppose they flew Air support for the British Admiralty in the 1700s? Or perhaps the method is as wanting as all the others..