by Dr Wilson Flood
Latest update: 18 Feb 2009
Figure 1 - Central England Temperature (CET) Record.
Figure 1(b) - CET since 2006 (ADDED 11 May 2008).
Figure 2 - The CET record compared to the average temp for 1961-90.
Figure 3 - Temperature record for the whole of England from 1914 to 2008.
Figure 4 - Comparison of the CET and the England record from 1914 to 2008.
Figure 5 - Annual difference between the CET and England records presented as a bar graph.
Figure 6 - Temperature record for Scotland from 1914 to 2008.
Figure 7 - Comparison of the CET with the Scotland record from 1914 to 2008.
Figure 8 - Annual difference between the CET and Scotland records presented as a bar graph.
Figure 9 - Temperature record for the UK from 1914 to 2008.
Figure 10 - Comparison the CET with the UK record from 1914 to 2008.
Figure 11 - Annual difference between the CET and UK records presented as a bar graph.
Figure 12 - Annual rainfall totals and trendlines for England and Scotland from 1914 to 2008
Figure 13 - UK land temperature and average sea surface temperature (SST) anomaly 1982-2006.
Figure 14 - Monthly HadCRUT3v temperature record from 1850 to the present day
Starting in 1659, the Central England Temperature Record (CET) is the world's longest continuous temperature record. The temperature is an average based on three sites. At present the sites are in rural locations in Hertfordshire, Staffordshire and Lancashire. The growing urbanisation of England has meant that the sites have to be moved from time to time to counter the urban heat island (UHI) effect. The record over-represents the warmer southern and western England and under-represents the cooler northern and eastern England. Nevertheless it is a valuable guide to how temperatures have changed in the last 350 years.
The cooling at the end of the Maunder minimum can be clearly seen in this line graph along with the sudden recovery after 1695 leading to a relatively warm 18th century. (It is a fact that 18th century CET summers were on average warmer than 20th century CET summers.) The 18th century was followed by a cooler 19th century noted for three quite cool periods in the 1810s, the 1840s and the 1890s. The 20th century starts cool, warms from 1920 to 1950 and then a cooling sets in which lasts until 1986. This is followed by a warming which has lasted until 2008. This is followed by a warming trend culminating in 2006 being the warmest year in the record. The years 2007 and 2008 have been cooler, the latter being nearly a full degree centigrade cooler than 2006.
The CET for April 2008 is 3.3 degrees lower than that for April 2008. This also marks 12 consecutive months in which the average monthly CET has been below that of the corresponding month in the preceding year, which appears to be a first for the CET record even during cold periods such as 1816.
UPDATE - This sequence of being cooler was broken in May 2007, which was a warm and sunny month, and that's a reminder that simple natural forces drive temperatures. However, in five of the last seven months of 2008 the cooling trend reasserts itself.
This bar graph shows annual temperatures compared to the arbitrary average temperature for 1961 -1990. The blue colours gradually recede over time as the climate slowly warms. There is then the appearance of a block of warmer than average years starting in 1990 indicating a sudden warming. Another feature of recent years has been a lack of temperature variability. Prior to 1990 annual average temperatures could typically fluctuate wildly over a range of 2 degrees or more from one year to the next. Since 1990 such fluctuations have disappeared and, far from climate chaos, climate stability seems to be the order of the day.
Starting in 1914, the UK Met Office has kept more extensive records of temperature and rainfall for the different parts of the UK, i.e. England, Scotland, Wales and Northern Ireland. It has also combined these records into a composite UK record. This chart shows how temperatures have changed from 1914 to 2008. Given the hysteria about climate change in the UK press one might have expected a more dramatic rise in temperature. The graph shows that there has been a rise in temperature of about one centigrade degree which broadly matches the global picture. There has been a series of warm years in the last decade but the warming is largely due to warmer winters rather than summers. Although the summers of 2003 and 2006 were warm, recent summers have mostly been only slightly above the long term average summer temperature.
Figure 4 - Line graph comparing the CET with the England record from 1914 to 2008.
The graph shows that the annual difference between the CET and England records is small and fairly constant as might be expected apart from two periods. In the mid to late 1970s warmer temperatures in the CET record were not reflected in the England record as a whole. Also from 1995 to 2007 the anomaly between the records has been steadily diminishing suggesting that the north of England has been warming relative to the south. This is probably related to a warming trend in the North Sea during this period (see Fig 13 for data to 2006). This would affect the England record more than the CET record.
The graph shows that the climate warmed slightly in the 1930s, 40s and 50s. There was then a cooler period until the mid 1980s since when there has been a gradual warming. Scotland does not enjoy a warm climate. The coolest summer months in this record are colder than the warmest recorded summer months in southern Greenland. Hence the Scottish public are not unduly alarmed by the prospect of "global warming".
The similarity between the two graphs is surprisingly good although temperatures in Scotland are about 2.4 degrees lower, much cooler than the England record (see Fig 4). The correlation between the two records is greater than 0.92. In the 1990s the temperature difference increased slightly because Scotland was cooler relative to England during that decade but since then the difference has reverted to a value close to the long term average.
It is immediately apparent that the temperature difference between these two records is much greater than that for the CET and England records. There is little variance in temperature difference until 1990 following which the temperature difference between the Scotland and CET records increases noticeably. After 1995 the temperature difference begins to return to more typical values. Actual temperature data shows this is due to Scotland warming slightly relative to England. Once again this may be caused by increases in sea temperatures which affect Scotland more than England due to its highly indented coastline.
The Met Office also produces a temperature record for the UK as a whole based on a weighted average of the four separate records for England, Scotland, Wales and Northern Ireland which takes account of their relative geographical areas. The record shows a fairly constant average temperature from 1914 until the 1980s since when there has been a slight warming. Once again this is probably related to rising sea temperatures around the UK during this time (see Fig 13).
The CET and UK records replicate each other almost perfectly, somewhat surprisingly given the geographical spread of the latter. The correlation between them is very high at nearly 0.99. Overall, as might be expected, the average UK temperature is cooler than the average temperature for the CET record, the difference being about one degree. More significantly, it could be argued that the close similarity between the two graphs makes the CET record an excellent proxy for UK temperatures back to 1659.
There has been remarkably little variation in the difference between the UK and CET temperature records from 1914 to 2007. A brief increase seen in the 1990s is no longer apparent by 2003.
As well as being colder than England, Scotland is also much wetter, with an average rainfall close to twice that of the average in England. This overall picture hides wide variations in rainfall patterns in both countries. The west is much wetter than the east and the north wetter than the south. South east Scotland has levels of annual rainfall that match those of south east England but rainfall levels in north west Scotland can reach 4500 mm per annum. In recent years, fuelled by alarmist newspaper articles about "climate change", the perception has grown that England's climate is becoming much wetter. The record shows that this is not so. The trendline is actually declining very slightly. In recent years there have been some rainfall events where a large amount of rain has fallen in a short space of time resulting in localised flooding of towns but total average rainfall levels remain relatively unchanged. Heavy rain is not uncommon in Scotland and, in contrast to England, there has been a definite increase in rainfall totals over the period of the graph. Once again these changes in rainfall patterns are consistent with recent warmer sea temperatures.
The temperature anomaly is the annual deviation from the 1982 -2006 average and the SST anomaly is derived from a comparable period. This chart shows that SSTs and temperatures have followed each other closely over the period being graphed. The correlation value is just under 0.87. By the nature of such things land temperature is influenced by sea temperature rather than the other way round given the greater thermal capacity of the latter compared to the former. We can see in both sets of data that the recent warming was preceded by cooler spells in the 1980s and 1990s. These cooler spells were probably influenced by the volcanic eruptions of El Chichon and Mount Pinatubo. However the warmest year in the global records, 1998, does not feature. In the UK 1998 was unremarkable and it is perhaps relevant to note that the seas around the UK for that year were not particularly warm either. It could be argued from this that the SST controls UK temperatures more effectively than amounts of carbon dioxide in the atmosphere.
This HadCRUT3v record shows how global temperatures have deviated on a month by month basis from a nominal mean which is the average temperature from 1960 - 90. It is based on a network of weather stations around the globe. This network has changed over time and because of this and other changes the line graph should give some indication of the statistical uncertainty of these readings. This is not provided. The line graph has therefore to be considered as the median of a set of possible values whose range is not known. Nevertheless it is a useful guide to how global temperatures have moved in the last one and a half centuries.
That there has been a warming in the 20th century is not in dispute. However just recently there has been a cooling trend which effectively started in 1998. This trend accelerated sharply in 2007 and by January 2008 most of the warming of the 20th century had been wiped out. It remains to be seen whether this is a temporary blip or whether it signals the beginning of a new but somewhat unscripted episode in the ongoing climate change saga. According to this record 2008 was the coolest year of the 21st century. (Note: 2000 is the last year of the 20th century).