You change the data. The world's oldest continuous temperature database is the Central England Temperature record which dates to 1659 (!). The CET has been recently updated to version 2. And along the way, something really interesting happened:
This is the year-by-year change that was introduced in V2. You can see kind of random up/down adjustments for hundreds of years right up until 1970. Then you see massive adjustments. The upward warming trend from 1970 to the present day is not due to the data as read, but rather to the (made up) adjustments to the data.
Conclusion: Man-made Global Warming is confirmed!* But it's not observable in real life, but only in computer print outs ...
I'm well past the point of giving the benefit of the doubt to the "Scientists" who do this (and have done this for ages, all over the world). Now the only explanation that makes sense is that Government wants to scare everyone with "Climate Change" and Scientists are giving governments what they paid for.
Back in the real world, we're still not seeing new high temperature records being set, even with each year as "one of the 10 hottest in the last 1000 years". The highest temperature ever recorded in these United States was in 1913, 111 years ago. That's some righteous warming that we're seeing right here.
Go read the very first link at the top of this post, which also delves into just how dodgy the data inputs are (poorly sited weather stations recording heat from RAF jets). Just like the US Surface Stations Project, he shows that the weather stations in Blighty are not fit for purpose. So bad in fact that the stations are trying to detect a warming signal of 0.1 degree/decade when the margin of error of the station is 4 or 5 degrees.
There's a reason that I have a post tag here called Climate Bullshit. And there's a reason that I don't post much anymore about Climate "Science" - it makes me grumpy.
Hat tip to Perry de Havilland at Samizdata.
* The chart there from the US Government weather bureau NOAA is essentially identical to the one shown above for CET. This game is being played everywhere.