Applying ages to our cores is central to all the research we do. If we don’t know how old our cores are, then all we have is a record of past changes without context or the ability to compare to other records. In general, the work we do covers a period in time known as the Holocene – this refers to approximately the past 11,500 years and is the period since the end of the last ice age. But depending on where we are working and when local peat formation began, cores may cover all of this period, just the past hundred years, or anywhere in between.
There are many different techniques that can be used to date the peat – to apply an age to any given depth of a core. We can figure out ages pretty accurately, but none of the methods are perfect, so ages always have error associated with them. For example, we might say the age of a sample at 100 cm depth is 950 – 1000 cal. BP. ‘Cal’ means the age has been calibrated – you can find out what that means below. ‘BP’ means Before Present. Confusingly, the ‘present’ is set at 1950, so as I write this in 2013, we are living in -63 BP!