Answer:
Most definitely 1950 to 2000; the sharpest and highest spike is there.
Explanation:
This is just based on the image of the graph, and the number of sunspots correlates with the amount of solar radiation. Also this fits with the theory/phenomenon of global warming and increasing radiation from the sun, which is some outside knowledge that supports this.
Hope this helped, and hope you're doing ok amidst these ongoing conflicts today. :)
