Testing for spatial dependence between independently measured values in an ordered set is based on applying Fisher’s F-test to the variance of a set and the first variance term of the ordered set. Charting statistically significant variance terms gives a sampling variogram that shows where spatial dependence in our sample space of time dissipates into randomness. The lag of a sampling variogram is a statistically robust measure for a change in a climate statistic.Scientists use "Indicator time series" that represent the many aspects of climate and ecosystem status. The time history provides a historical context. Current status of the climate is also monitored with climate indices
Evidence for climatic change
Evidence for climatic change is taken from a variety of sources that can be used to reconstruct past climates. Most of the evidence is indirect—climatic changes are inferred from changes in indicators that reflect climate, such as vegetation, dendrochronology, ice cores, sea level change, and glacial retreat
