Scientists at two of the world’s leading climate centres - NASA and NOAA - have been caught out manipulating temperature data to overstate the extent of the 20th century "global warming".

Breitbart

Scientists at two of the world’s leading climate centres - NASA and NOAA - have been caught out manipulating temperature data to overstate the extent of the 20th century "global warming".

The evidence of their tinkering can clearly be seen at Real Science, where blogger Steven Goddard has posted a series of graphs which show "climate change" before and after the adjustments.
When the raw data is used, there is little if any evidence of global warming and some evidence of global cooling. However, once the data has been adjusted - ie fabricated by computer models -  20th century 'global warming' suddenly looks much more dramatic.
This is especially noticeable on the US temperature records. Before 2000, it was generally accepted - even by climate activists like NASA's James Hansen - that the hottest decade in the US was the 1930s.