They are making sure what current readings of the isotopes in ice cores actually mean in terms of what was in the air when the ice core was formed years ago.
(They; are making; sure what current readings of the isotopes in ice cores actually mean in terms of what was in the air) (current readings of the isotopes in ice cores; actually mean; ) (the ice core; was formed; T:years ago)
They current readings of the isotopes in ice cores the ice core
are making actually mean was formed
sure what current readings of the isotopes in ice cores actually mean in terms of what was in the air
T:years ago