by Dr Wilson Flood
Latest update: March 2010
Figure 1 - Central England Temperature (CET) Record.
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 2009.
Figure 4 - Comparison of the CET and the England record from 1914 to 2009.
Figure 5 - Annual difference between the CET and England records presented as a bar graph.
Figure 6 - Temperature record for Scotland from 1914 to 2009.
Figure 7 - Comparison of the CET with the Scotland record from 1914 to 2009.
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 2009.
Figure 10 - Comparison the CET with the UK record from 1914 to 2009.
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 2009.
Figure 13 - UK land temperature and average sea surface temperature (SST) anomaly 1982-2006.
Figure 14 - Monthly global temperature record (HadCRUT3) from 1850 to the present day
Figure 1 - Central England Temperature (CET) Record.
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 as 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 started
cool, warmed from 1920 to 1950 and then a cooling set in which lasted
until 1986. This was followed by a warming trend culminating in 2006
being the warmest year in the record. The years from 2007 onwards have
been noticeably cooler with 2008 being nearly a full degree centigrade
cooler than 2006.
Figure
2 - The CET record compared to the average temp for 1961-90.
This bar graph shows CET annual temperatures compared to the arbitrary average temperature for 1961 -1990. The blue colours gradually recede over time as the climate slowly warmed after the Little Ice Age. 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.
Figure 3 - Line graph showing the temperature record for the whole of England from 1914 to 2009.
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 2009. Given the hysteria about climate change in the UK press one might have expected a more dramatic rise in temperature. The graph shows that in England there has been a rise in annual average temperature of about one centigrade degree which broadly matches the global picture. There was a series of warm years in the last decade but the warming was largely due to warmer winters rather than hotter 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 2009.
As one might expect the two graphs follow each other
very closely with a correlation of greater than 0.99. The England
temperature record takes in the whole country and is slightly cooler
than the CET record because the England record includes weather data
from the cooler north and north east of the country whereas the CET has
a bias to the warmer south of England.
Figure 5 - The annual difference between the CET and England records presented as a bar graph.
As might be expected, the graph shows that the annual difference between the CET and England records is small and fairly constant 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 2009 the anomaly between the two records has been diminishing. Inspection of temperature records shows that the north of England has been warming relative to the south. This could be 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.
Figure 6 - Line graph showing the temperature record for Scotland from 1914 to 2009.
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 were
colder than the warmest recorded summer months in southern Greenland.
Hence the Scottish public are not unduly alarmed by the prospect of
"global warming".
Figure 7 - Line graph comparing the CET with the Scotland record from 1914 to 2009.
The similarity between the two graphs is surprisingly good, given the geographical separation between Scotland and central England, although temperatures in Scotland are on average 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.
Figure 8 - The annual difference between the CET and Scotland records presented as a bar graph.
It is immediately apparent that the temperature difference between these two records is much greater than that for the CET and England records. There was little variance in temperature difference until 1990 following which the temperature difference between the Scotland and CET records increased noticeably. After 1995 the temperature difference began to return to more typical values. Actual temperature data shows that the difference increase was due to England warming relative to Scotland followed by a period when Scotland warmed slightly relative to England.
Figure 9 - Line graph showing the temperature record for the UK from 1914 to 2009.
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, taking account of their relative geographical areas. The record shows annual average temperatures rising then falling from 1914 until 1986. Between 1986 and 1990 there was a sharp jump in temperature, seen in all the other UK temperature records. After 1990 temperatures stabilised at this higher level. Once again these latter changes could be linked to rising sea temperatures around the UK during this time (see Fig 13).
Figure 10 - Line graph comparing the CET with the UK record from 1914 to 2009.
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.
Figure 11 - The annual difference between the CET and UK records presented as a bar graph.
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 was no longer apparent by 2003.
Figure 12 - Line graphs showing annual rainfall totals for England and Scotland from 1914 to 2009 along with linear trendlines for the period.
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 flooding that took place in parts of northern England and southern Scotland in
the autumn of 2009 might seem to confirm that the UK climate is becoming wetter. The graphs show that 2009 was less wet than 2008 in Scotland and significantly less wet than 2007 and 2008 in England.
Figure 13 - UK temperature anomaly v. UK average sea surface temperature (SST) anomaly 1982-2006.
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.
Figure 14 - Monthly global temperature record ( HadCRUT3) from 1850 to the present day.
The HadCRUT3 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 shown. The line graph has therefore to be considered as the median of a set of possible values. Nevertheless it is a useful guide as 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.