In a letter to Nature - you could say this is an analysis of the most studied series in climatology. Thousands of people have looked at the data - and no-one has noticed this before!
Aside - If the skeptics had been doing their job properly and didn't start from a biased base, they might have spotted it !!! They start from the premise that the series is wrong. They will be kicking themselves to have missed this. I've always said it is WW2.
It Must Have Been Spring – But It’s Over Now
28 minutes ago