Trend

A long-term change in a time series which extends outside the normal range of variability.

In detail

A trend usually refers to a general direction, course or tendency. However in discussions of climate variability and climate change projections a trend means a change in the value of a variable over time, usually in one direction only. UKCP09 presents information both about observed trends in recent UK climate and projected trends in future UK climate, using a variety of data sources.