Index Value Plot

http://wattsupwiththat.com/2009/08/17/evidence-that-ocean-net-heat-flow-is-connected-with-climate-shifts-co2-not-correlated/

This index value plot shows the monthly values for the PDO (Pacific Decadal Oscillation) Index between January 1900 to September 2008. The red, positive index values indicate a warm phase wile the blue, negative index values indicate a cooler phase. This plot shows that PDO phases generally persist for 20-30 years. An index value plot is a type of visualization map in which an index value is plotted on a line graph.