"I've seen similar colourful pictures made to look like graphs. I even tracked down the website of the artists, neither of whom disclose Science based credentials. I didn't find the graph but I did find a copyright notice. Is this work of art posted with the original artists permission I wonder?"
lol, that made me laugh.
perhaps you can ask climatologist Cliff Harris & meteorologist Randy Mann as they prepared the chart. the sources that they used to compile the chart were,
"Climate and the Affairs of Men" by Dr. Iben Browing.
"Climate...The Key to Understanding Business Cycles...The Raymond H. Wheeler Papers. By Michael Zahorchak
Weather Science Foundation Papers in Crystal Lake, Illinois.
