The cable would be covered with ice where it is expected that it would be subjected to a stable minus 50 deg C.

BBC: Internet to reach South Pole

But there is geological evidence that this figure has been down to about 7 deg C and possibly as high as 27 deg C.

BBC: Looking for the greenhouse signal

There is also no way a whole decade in the LIA period was more than 1 deg C on a global basis cooler than the 1961-90 mean.

WSJ: Climate Emails: Science and Candor