Temperature in the US has been declining for some time. The peak was in the 1930's around the time I was born. James Hansen of NASA/GISS has applied some magic algorithm to the historical data that no one else understands but it reduced past temperatures a lot from what was actually recorded. Worldwide the number of recording stations has been significantly reduced, particularly in Russia, since 1990. Some of the evil people in the pay of Big Oil and flat-earth kooks have noted that surface temperature took a big uptick about that time. But, Hansen and other warmers assure us that they make adjustment to the record to accurately reflect what those inoperative stations would have recorded. And, of course there is no possibility that they suffer from "confirmation bias" as they make the adjustments. (In my career as an engineer I saw many examples of smart guys with PhD's being afflicted with confirmation bias; it can happen to a group of bright people.) Here is an article that compares the raw surface temperature data for the US with Hansen and companies adjusted data. Note that the raw data show a cooling trend while the adjusted data show the warming trend expected by Hansen. (North America is the only place with reasonably accurate temperature monitoring stations covering the entire region, so probably gives a better view of the actual trend than the purported world wide data, which involves interpolation over huge regions.)

http://www.americanthinker.com/blog/2009/01/global_warmmongering_more_silk.html