I was looking at this yesterday and learned the following. A 100 year flood is a flood that has a 1% chance of happening in a given year. A 500 year flood has a 0.2% chance of happening in a given year. I’m not sure if temperature has the same model as rainfall. Anchorage was settled in 1914 according to Wikipedia, so I’m assuming that there are no temperature records beyond that and that 100 years in this case refers to it only having been settled for about 100 years.
So I guess there is no scientific reason, just living memory. For me such articles just lack the scientific merit and the only purpose is trying to cause mass hysteria. Earlier it was about how we all going the freeze to death, nowadays it is how we are all going to die because of global warming. In fact Earth went through several warm and cool periods, even if you look back just few hundred years. I am all for reducing CO2 and I am pretty successfully reduced unnecessary CO2 production in my work by using more efficient solutions and not wasting energy because this is what is under my control to help mother Earth. Writing click baity articles without context and scientific merit is not going to help anybody.
To cause "hysteria" in the way you're implying the general public would have to read the headline any other way than it is meant in the first place. But joe shmoe wasn't ever going to consider that 1000 years ago earth may have been in a different place climate wise so they're going to read the headline exactly the same whether it has the qualifier "in recorded history" or not.
Or maybe it’s only you who considers it clickbait and everybody else immediately understood the article was about recorded history of temperatures, because, you know, it’s kinda common sense?
"Moore co-chaired the Clean and Safe Energy Coalition, which was supported by the Nuclear Energy Institute, a national organization of pro-nuclear industries.[59] In 2009, as co-chair of the Coalition, he suggested that the mainstream media and the environmentalist movement is not as opposed to nuclear energy as in decades past.[59]
He argues that any realistic plan to reduce reliance on fossil fuels or greenhouse gas emissions would require increased use of nuclear energy to supply baseload power."
