Slide 8: Palaeoclimatological time scale
Palaeoclimatological proxy data provides us with useful information over different time periods. Looking at the data from the most recent to the longest time periods, we can see that historical data cannot give us useful information much beyond a thousand years
Tree rings and pollen provide data up to several tens of thousands of years, and some ice cores show records up to almost a million years.
Some ancient glacial deposits were laid down by movements in the tens of millions of years, and marine organic and inorganic sediments provide data up to several hundred million years ago.
Some sedimentary rocks were laid down several billion years ago.
It is important to note, however, that the resolution (and to some extent, the accuracy) of these data decreases as we look further back in time.