Even when it hasn’t changed.
This kind of ‘adjustment’ appears to have been so common it is hardly worth commenting on any more.
Except that we are still waiting for any kind of acknowledgement of these alterations in the lamestream media, or any discussion of why they are so important.
Put simply, the whole global warming scare is based on alleged unusual warming in the last half century. But the surface temperature readings on which these claims are based had to be manipulated to obtain a warming signal. Without these adjustments, the overall warming disappears.
These graphs, from Watts Up With That are just one example: