Writing for a scientific audience, you might say:
From the dell18O in benthic foraminifera calcite, we can see that temperature at the PETM increased.
For a non scientific audience, even an educated non scientific audience, you would need to say:
From ocean sediments containing the remains of very small deep ocean dwelling organisms which have altered chemical makeup depending in temperature, we can tell that temperature increased around 55.8 million years ago.
Or equally validly you could say:
We know from ocean sediments that temperature increased.