António Guterres, the Secretary General of the UN, and many other UN employees were killed when Jormungandr, the Snakebot of Doom steamrolled New York city in January 2017.
Now, in early February 2017, aliens have come to negotiate with the people of Earth, and the UN is the most logical body to deal with them on behalf of the whole world. However, the world has been thrown into disarray by Jormungandr's attacks, the UN offices in New York have been destroyed and many UN personnel are dead, and no official successor to the position of the Secretary General has been appointed.
So, my question is:
Does the UN have a chain of succession, and how can I work out who would be acting Secretary General? I'm not after the name of the real-life people who might succeed the UN Secretary General, I'm looking for the positions whose incumbents (whoever they are) would be selected as - or who could function as - the replacement Secretary General in an emergency, pending proper selection of a new Secretary General. In the event that there is no such person in the UN, or there is no clear chain of succession, is there any other person or group who could act in the UN Secretary General's stead?
The answer to this question is not 'trivially googled'... enter the wrong search terms, and you get nothing useful. Additionally, the UN website has many broken links. Finally, while this may seem to be a trivial piece of information for which a worldbuilder could search, the answer may be necessary for a person's worldbuilding effort. I certainly found it so for mine, unless I wanted António Guterres to have a miraculous escape when so many non-famous New Yorkers didn't.
To address another issue mentioned in comments, it doesn't matter that the UN doesn't have any power delegated to it by any nation, since the Secretary General is a required point of contact in the event of first contact with aliens.