I've been thinking about the butterfly effect and its effects on natural phenomena. Specificly, which timelines should keep particular evens such as the Kobe Earthquake or Hurricane Katrina. Here's my best guess, other opinions (and reasons, if any) very wanted. Earthquakes, my best guess is that they are very long term stable. The Kobe Earthquake will happen on schedule, barring author's fiat or major earth-shattering events. Underground nuclear tests are the only man-made events that I can see being enough to change a volcano or earthquake. (Although with a sufficiently early POD, a few centuries of water being drawn from a particular aquifer might just be enough to change the timing?) Hurricanes and other storms--much more variable. Differing levels of Carbon Dioxide could cause changes over a local area. Dresden burning or the like. For that matter, I heard that the absence of planes over the USA--and the absence of cloud-spawning contrails--may have made a difference in the cloud cover. I'd say a year or tow, at most, to have the option of butterflying a particular storm. But, I'd be inclined to keep overall patterns the same for longer--this year was a heavy hurricane year, etc. How much longer? I don't know.