In 1981, James Hansen of NASA published these graphs of surface temperatures. Note that northern latitudes and global both showed 1940 as warmest, with a sharp global cooling to the early 1970’s.

pubs.giss.nasa.gov/docs/1981/1981_Hansen_etal_1.pdf
But the current NASA graphs don’t look anything like that. Global surface temperatures no longer show any cooling from 1940 to 1970.

Data.GISS: GISS Surface Temperature Analysis: Analysis Graphs and Plots
I overlaid current GISS global surface temperatures (red) on Hansen’s 1981 version. Hansen massively cooled his own pre-1980 data, and added a huge spike in 1979.

Also note that Hansen has nearly wiped out all of his own 1940-1970 cooling.
Now let’s look at just the 24N-90N temperatures, current data in red. Hansen has knocked 0.2C off his own 1940 temperatures. The shape of the data is nearly identical, but NASA now adds an increasingly larger cheat factor of cooling to progressively older data.

Everyone agreed about the post-1940’s global cooling at the time, including Hansen. But Hansen and now Gavin have deleted it from the temperature record.

SCIENTISTS AGREE WORLD IS COLDER – But Climate Experts Meeting Here Fail to Agree on Reasons for Change – View Article – NYTimes.com
Leading climate scientists discussed with each other how to get rid of the 1940’s warmth, which might have impacted their ability to extort taxpayer money.
From: Tom Wigley <[email protected]>
To: Phil Jones <[email protected]>
Subject: 1940s
Date: Sun, 27 Sep 2009 23:25:38 -0600
Cc: Ben Santer <[email protected]>
<x-flowed>
Phil,
Here are some speculations on correcting SSTs to partly
explain the 1940s warming blip.
If you look at the attached plot you will see that the
land also shows the 1940s blip (as I'm sure you know).
So, if we could reduce the ocean blip by, say, 0.15 degC,
then this would be significant for the global mean -- but
we'd still have to explain the land blip.
di2.nu/foia/1254108338.txt
If the present refuses to get warmer, then the past must get much cooler.
* Mosher says this is all first rate science.