But as this useful and concise site notes, they’re using the word incorrectly. “Concerning” is a preposition synonymous with “about,” not an adjective which means “upsetting”:
People commonly say of things that are a cause for concern that they are “concerning”: “My boyfriend’s affection for his pet rattlesnake is concerning.” This is not standard English. There are many better words that mean the same thing including “worrisome,” “troubling,” and “alarming.”
The more a word is misused, the more people pick it up. (Go to any meeting of a local government body, and you’re almost certain to hear someone describe some worrisome trend as “concerning.”) So in another few years, grammarians who believe that language should be defined descriptively rather than prescriptively no doubt will argue that this incorrect usage should be added to our dictionaries, since that’s the way people have come to use it.
In Politics and the English Language, George Orwell famously (but not famously enough) argued not only that sloppy thinking causes sloppy expression, but also vice versa.
A man may take to drink because he feels himself to be a failure, and then fail all the more completely because he drinks. It is rather the same thing that is happening to the English language. It becomes ugly and inaccurate because our thoughts are foolish, but the slovenliness of our language makes it easier for us to have foolish thoughts. The point is that the process is reversible. Modern English, especially written English, is full of bad habits which spread by imitation and which can be avoided if one is willing to take the necessary trouble. If one gets rid of these habits one can think more clearly, and to think clearly is a necessary first step toward political regeneration: so that the fight against bad English is not frivolous and is not the exclusive concern of professional writers.
Listening to the news, reading the papers, and attending political meetings, one can only conclude that there’s a lot of confused thinking out there. And last week’s midterm elections only ratified that conclusion...