Measuring global temperature trend is not easy. First, almost every weather station is subject to daily temperature variation (which adds a lot of noise to the signal), second there is ubiqutous UHI effect. There are perhaps only two stations in the world that aren’t affected by these problems. They are Amundsen-Scott and Vostok located in Antarctica. They both have a similar historic temperature graphs, covering almost half a century:
http://www.nerc-bas.ac.uk/icd/gjma/amundsen-scott.ann.trend.pdf
http://www.nerc-bas.ac.uk/public/icd/gjma/vostok.ann.trend.pdf
Based on these trends calculate how long it would take for the average temperature to increase a puny one degree Celcius.
