Natural disasters and the Buddhist doctrine of karma
As sealwhiskers noticed, not everything happens for a reason (even though everything that happens gives us a reason to grow up). Similarly, according to Buddhist sources, not everything which happens to us is the result of karma (something that I probably fail to emphasize enough in my Eastern Philosophy classes). Here are two references to very early Pali sutras:
In the Devadaha Sutta (M.II,214, also A.I,173 ) the Buddha says that the belief that every experience we have is due to past kamma (sabbam tam pubbe katahetu) is a wrong and false view (miccha ditthi). In the Sivaka Sutta (S. IV,228) he says that the suffering we sometimes experience can be due to kamma but it could also be due to sickness, to weather, to carelessness or to external agents (opakkamikani).
HEAVILY EDITED:The quote is taken from a way worth reading essay by a Buddhist monk Shravasti Dhammika, "The Tsunami: A Buddhist View" ( http://sdhammika.blogspot.com/2011/03/tsunami-buddhist-view.html ).
here is a modern translation of Sivaka Sutta: http://www.accesstoinsight.org/tipitaka/sn/sn36/sn36.021.than.html
However, the translator Thanissaro Bhikkhu adds in his note what follows:
Some people have interpreted this sutta as stating that there are many experiences that cannot be explained by the principle of kamma. A casual glance of the alternative factors here - drawn from the various causes for pain that were recognized in the medical treatises of his time - would seem to support this conclusion. However, if we compare this list with his definition of old kamma in SN 35.145, we see that many of the alternative causes are actually the result of past actions.
So, it looks like we have here possibly some internal Buddhist dispute. However, Thanissaro do not claim that all such causes are the results of past karma. Furtherore, the Buddha himself is rather clear in his emphasis. For example:
So any priests & contemplatives who are of the doctrine & view that whatever an individual feels - pleasure, pain, neither-pleasure-nor-pain - is entirely caused by what was done before - slip past what they themselves know, slip past what is agreed on by the world. Therefore I say that those priests & contemplatives are wrong." (emphasis added)
Now, the Buddha could have said that they are partially wrong and their view requires some clarification. But he does not, he just flatly rejects such a view.
By the way, I myself doubt that every result is a result of karmic causes (i.e., the result of past, or current actions, or their combination). I do not see how such a view can be reconciled with the current science (When science conflicts with philosophy/ideology/religion, I always take the side of science; ideology is just to prone to prejudices.) In particular, the current quantum (subatomic) physics implies that there is true randomness in the universe. E.g., the decay of a particular atoms seems a purely chance (i.e., random) event. Similarly, quantum leaps of submicroscopic particles such as electrons seem completely random. In turn, those random events cave causal powers and affect sentient beings. So, right there, we have a strong reason to think that not every result is the result of karma.
Wen I have a bit more time, I will look for further sources to support the interpretation that, in Buddhism, not every result is the result of karmic causes. But, of the top of my head, several Pali sources address the problem of pain experienced by the Buddha and Arahats (i.e., deeply spiritually realized beings). For example, as a result of attack by Devadatta, the Buddha's foot is severely injured and he is immobilized for quite a while. The sutra is clear that this pain is not the result of karma, because the Awakened One has already exhausted his karma (that's why he is the Buddha). The sutra characterizes the pain as a result of other's will.