Very far from confirmed. I just finished reading [0,1] accounts of
atmospheric heat anomalies being touted as a cause - alongside
speculation about cyber-attacks. Something to remember about terrorist
groups and propaganda merchants, is that they'll claim
"responsibility" or otherwise misattribute acts immediately to gain
attention. Often the first thing reported is what sticks in the public
mind.
My childhood was in the 1970s and 80s when the 'Troubles' [0] affected
Britain, Northern Ireland and the Irish Republic. There were a
dizzying number of factions, paramilitaries, volunteer groups,
splinter groups... In those times it was rather common for killings and
other actions to be mis-claimed, or tactically denied, with specious
bomb threats or actual terror acts blamed on a different group. It was
a very complex situation, as smouldering war zones usually are.
Eventually the leaders from various camps developed codewords and
protocols, so that for example the IRA or UVF could message MI5 and
have a bomb warning taken seriously, or properly attributed in
reporting. Many things that happened in those days were not at all
clear cut and remain unknown to this day who really did what. Based
on this I would counter that clarity is the exception.
And if you think about that, it makes sense. What's the point? The eventual loss of credibility is not worth it for any serious group.
Usually what happens is that they are not believed at first, and then mounting evidence confirms the claim