HadCET CUSUM analysis

From Factsheets: Limiting UK Emissions
Jump to navigation Jump to search

CUSUM analysis - a statistical technique borrowed from the quality control discipline - is deceptively simple to calculate by spreadsheet or even by hand yet a powerful tool for screening out 'noise' and spotting trend changes

  1. calculate the deviations from mean average
  2. first value = 0
  3. second value = first value + first deviation
  4. third value = second value + second deviation
  5. and so on
  6. final value = 0 by definition of average must be so

The thing to look for is abrupt kinks in the graph, which shout 'something changed here'. The chart below - original work by FLUKE - appears to show four distinct trend periods: 1772 to 1892, 1892 to 1932, 1932 to 1988 and 1988 to present