Andrew Weaver is a climate scientists at the University of Victoria (he is mentioned earlier in the article).
However Weaver's comments are in reference to Hansen's report (which I do not believe specifically focused on this years temperatures in the USA). I would imagine the report offers a longer term review of climate events (as suggested by the article and Weaver's comments).
So no scientists argues (in that article) that the March temperatures are evidence of global warming. The closest you get is: "NOAA climate scientist Gabriel Vecchi compared the increase in weather extremes to baseball players on steroids: you can't say an individual home run is down to steroids, but they are hit more often and the long-held records for home runs fall."
The only real direct quote was this by Weaver who could be a skid row bum or a nobel prize winner bur is not identified as a scientist,
Weaver, who reviewed the Hansen paper and called it 'one of the most stunning examples of evidence of global warming.'
As for Daily Mail, deniers often point to articles there, but there are often mis-quotes or info taken out of context. frequently the comments and quotes aren't really identified as to the source or credentials. Most of the time the headline is sensational but really contains no real science to back up the headline. It is seen as a denier rag by many. I did look at this article but generally when I see dailymal I don't even bother to click the link.
While individual events can't be blamed on global warming, some scientists believe this is like the extremes that are supposed to get more frequent because of man-made climate change from the burning of fossil fuels such as coal and oil.