Connect-The-Dots: Global warming statistics have been heavily manipulated to conform to alarmist scientists expectations - wholesale fabrication takes place because of the infamous "the models told me to do it" rationale
(click on images to enlarge, source)
Read here. The manipulation of temperature datasets, by climate alarmist scientists, to bolster the case for anthropogenic global warming has been discussed often at 'C3' and is even admitted to by those with close association to the Climategate fiascoes.
Phil Jones: ‘The instrumental records we examined seemed to be showing warmer temperatures than our computer models indicate should have occurred. We have therefore adjusted the instrumental record.’ (source here and here)
One of the simplest means to bolster the case for modern global warming, after 1950, is to "adjust" temperatures down (i.e. cool them) prior to 1950 - voila, modern global warming is enhanced by data manipulation alone. As can be seen in the above images for several individual EU climate stations, the blue lines represent the original temps and the red curves, pre-1950, the "cooling" adjustments for the period of 1920 to 1950 are obvious.