It's something that we wanted to show too. Apart from the technical complexity involved it would be hard to show warming. In the last century overall warming was maybe 1 deg C, but temperatures fluctuate from year to year by up to 15 degrees. Here is a delta graph for 1900 - 2012, for example: https://www.evernote.com/shard/s5/sh/6d1d932a-c1ed-411d-9b74... One way of doing it though would be to use a rolling average of, say, 5 years.