In 1975, all climatologists understood that there was tremendous warming prior to 1940, and a large amount of cooling after 1940.
This pre-1940 warming and post-1940 cooling didn’t suit the political needs of NASA under Barack Obama, so they erased it. As you can see in the graph below, the actual data completely wrecked the story, so they wiped out most of the pre-1940 warming.
This destruction of the data did not happen by accident. Climategate E-mails show that scientists removed the 1940’s warmth on purpose.
From: Tom Wigley <firstname.lastname@example.org>
To: Phil Jones <email@example.com>
Date: Sun, 27 Sep 2009 23:25:38 -0600
Cc: Ben Santer <firstname.lastname@example.org>
It would be good to remove at least part of the 1940s blip, but we are still left with “why the blip”.