The UK Met Office long term Central England Temperature record has kept a continuous and consistent data set since the 1660s. It appears to be reliable and to have maintained its quality. It has not been adjusted as have so many other official temperature records.
Although the CET record covers only a small part of the northern hemisphere, it has shown a consistent rise since the end of the little ice age in 1850 at a rate of about +0.45°C / century or about +0.67°C in the last 150 years. This rise accords well with other temperature records.
However since the year 2000, diminishing solar activity in solar cycle 24, moving back towards little ice age patterns, appears to be having an real effect.
So since 2000 the CET shows an annual temperature diminution at the rate of -0.49°C / decade or -0.59°C in 12 years: this negates ~80% of the entire CET temperature rise since 1850. Although this is a very short period, the extent of the climate change that has been observed since the turn of the millennium is remarkable.
Using the March 2013 CET value it is possible to show the winter temperature values up until March 2013 with a combination of the four months December – March for the first 13 years of this century. The diminution of the four winter months temperatures is more remarkable at a rate of -1.11°C / decade or -1.49°C in the last 13 years. This compares with a winter temperature increase rate from 1850 to the year 2000 of +0.32°C / century or +0.48°C for the whole 150 year period.
There are substantial shorter term fluctuations in temperature and since about 1850 world temperatures have been recovering from a Little Ice Age up by about +0.7°C up until the year 2000. These fluctuations have correlated well with solar activity observable by the number of sunspots. There was a particularly active solar period from about 1970 onward coinciding well with sunspot cycles 21 – 22 – 23: it lead to comparatively rapid warming.
However the current cycle 24 is very much weaker and sunspots are diminishing to the levels of the earlier Little Ice Age.