Span and Resolution

Not all climate proxy data is created equal. Different sources of data can cover larger or smaller time spans, depending on their age. In addition, each has a different resolution. This is a way of saying how detailed the samples are. For example, ice cores have nice, clean layers for each year of snowfall, while ocean sediment cores are less detailed due to compression over time. In general, as a sample of proxy data gets older, the resolution decreases.

Source: NOAA