Earth Science?

Question

Explain how pollen and plankton assemblages are used to measure past climate.

Answer 1

I don't know a thing about pollen.  I do know that one way of measuring past climates is to look at the chemical isotopes that are still present in the hard parts of plankton.  Plankton will use preferentially the isotopes of carbon and oxygen that are the most plentiful in the atmosphere to form hard parts.  This can then be calculated as a representation of the chemicals concentration in the atmosphere.

Answer 2

The make up of the flora and fauna is partly dependent upon the climate.  Therefore, that's an influence on the pollen and plankton that were available for fossilization.