The 30's were brutal ,a sudden change in weather patterns that hurt peoplePretty much your link says the graph is correct... and tries to quibble that it might be comparing apples to oranges before & after 1960. Yet they can't say why the data before and after 1960 is not comparable,
I'll simply go with what my grandparents said about the 1930s -- they never experienced a hotter time in the U.S., the west was a dust bowl, and forest fires regularly burned across the U.S. due to the heat &storms.
The gradual change we see now should allow us to adapt and mitigate......Canada can look forward to a good Soybean crop , something they cant do now
Generally Homo-Sapiens have thrived once temperatures started warming after the last ice age