Change-point analysis
Example: Change-point analysis (nonlinear regression).

Comparison of the oxygen isotope record from stalagmite Q5 (Oman), a proxy for monsoon rainfall changes, with the smoothed (five-point running mean) oxygen isotope record from the GRIP ice core (Greenland), an indicator of North Atlantic air-temperature variations. Lower monsoon precipitation correlates with colder North Atlantic temperature. The heavy lines show fitted nonlinear 'ramp' functions as trend estimate. Change-point times are given with their statistical errors (1 sigma), which are estimated from bootstrap simulations. Taking dating uncertainties for both the Q5 and GRIP records into account (1% to 2%) shows that the changes occurred simultaneously. BP, before the present.

Source: Fleitmann D, Burns SJ, Mudelsee M, Neff U, Kramers J, Mangini A, Matter A (2003) Holocene forcing of the Indian monsoon recorded in a stalagmite from Southern Oman. Science 300:1737. External link to paper >>

Software: RAMPFIT. Climate change analysis software >>