One theory associates regional decline at the end of the Akkadian period (and of the First Intermediary Period following the Old Kingdom in Ancient Egypt) was associated with rapidly increasing aridity, and failing rainfall in the region of the Ancient Near East, caused by a global centennial-scale drought. Harvey Weiss has shown that Peter B. deMenocal has shown "there was an influence of the North Atlantic Oscillation on the streamflow of the Tigris and Euphrates at this time, which led to the collapse of the Akkadian Empire". More recent analysis of simulations from the HadCM3 climate model indicate that there was a shift to a more arid climate on a timescale that is consistent with the collapse of the empire.