Thompson et al said that "their [Thompson's four Tibetan ice core] dO18 histories or proxy temperature records, are remarkably similar at lower frequencies". They are not just similar – they are "remarkably similar" with correlations as high as one milllll-ion.
The top is a spaghetti graph of the four dO18 series (5 year averages as saved by Thompson); the bottom is the same with 5-point smoothing. As you can see, the similarity of the series is breath-taking; no wonder Thompson et al call it "remarkable". Unlike ordinary similarity where correlation cannot exceed, "remarkable" similarities are said by Dr Evil to have an r2 of one millllll-ion. (As I was watching the presentation of this information, No. 2 interrupted the telecast to mention that, for example, the correlations of Guliya to the other ice cores ranged from -0.05 to +0.05, in both cases. )
Top: Four Tibetan Plateau dO18 series (5-year averages), all centered. Bottom – Same with 5 point gaussian smooth