Two long sentences. please help me to understand them. thank you so much!
1.we now have hundreds of tree-ring records from throughout the northern hemisphere, and many from south of the equator, too, amplified with a growing body of temperature data from ice cores drilled in Antarctica, Greenland, the Peruvian Andes, and other countries.
a)how to understand "too" and also "amplified with a growing body of temperature data from ice cores drilled in Antarctica, Greenland, the Peruvian Andes, and other countries."?
b)what does "drilled" mean here?
c)how to understand the whole sentence.
2.it was not a time of uniform warmth, for then, as always since the Great Ice Age, there were constant shifts in rainfall and temperature.
a)how to understand "for then" here
b)does "as" here mean "because