by Tony Brown
A warming trend can be observed from 1659, the start date of Central England Temperature (CET)- the oldest instrumental record in the world- to today. It would be a notable coincidence if the warming started at the exact point that this record began. The purpose of this paper is to reconstruct CET from its current start point, through the use of diverse historical records, to 1538, in order to see if the commencement of this centuries long warming trend can be identified from within this time frame.
Figure 1 CET from 1659-in the style of Hadley 1772
Retracing our climatic steps provides an opportunity to revisit the respective works of Hubert Lamb and Dr Michael Mann- both famous for their reconstruction of temperature records- in the light of the evolving science and additional information that has become available over the last few decades. This paper re-examines some of their best known work, notes how each has influenced the debate over our climate, and places their contributions into the overall context as background to our own reconstruction.
Section 1 Dr Mann’s reconstruction of Climate History
Dr Mann’s view of our past climate-epitomised by the iconic 1998 ‘Hockey stick-’ contradicted in substantial part the work of Hubert Lamb, the founder and first director of CRU from 1972,) who had died one year previously. (1)
Dr Michael Mann, born in 1962, is currently Professor of Meteorology at Penn State University in the US. (2)
Hubert Lamb (born 1913) produced a number of books and papers during his long career as arguably the leading climate scientist of his era, of which the most influential was probably ‘The Early Medieval Warm Epoch and its Sequel’ published in 1965. (3)
Within this work was a pre computer era graph based on CET and other English records. It was probably derived from earlier work that was only published years later, as Figure 30 Chapter 5 of his 1982 book, ‘Climate History and the Modern World.’ The 1965 version was substantially re-interpreted by the IPCC for their 1990 assessment and used on page 202 Figure7c as the basis for a global record. Figure 2 below shows the (unattributed) version of the graph used by the IPCC
Figure 2
Below is a variation showing winters only.
Figure 3 This shows winter severity in Europe, 1000 – 1900. Note two cold periods in the 15th and 17th centuries. Based on Lamb, 1969 / Schneider and Mass, 1975.
The convoluted transformation of the original graph from Lamb’s version (Figure 2) into the one used by the IPCC is documented here. (4)
Dr Mann, together with colleagues Bradley and Hughes, used instrumental data from 1902 to 1998, (the date of the study) together with a variety of proxies such as tree rings, in order to reconstruct a Northern Hemisphere record of temperature anomalies back to the year 1400. Their April 1998 paper published in ‘Nature’ entitled ‘Global Scale Temperature Patterns and Climate Forcing over the Past 6 Centuries’ became known as MBH98. Figure 5b in the link here (5) illustrates their reconstruction the most clearly.
The following year the same authors produced an article entitled ‘Northern Hemisphere Temperatures during the last Millennium: inferences, uncertainties and limitations’. Published in The American Geophysical Union magazine in 1999 it extended the work of the 1998 paper by 400 years to 1000AD. The paper became known as MBH1999. (6)
The third IPCC assessment in 2001 subsequently adapted their figure 3 from this later 1999 work and it is this iconic version, which later came to be known as the ‘hockey stick,’ that is still much used to illustrate the apparent effect of human activities on temperature in recent decades, specifically through the release of co2.
Figure 4 (Figure 2.20:_ Millennial Northern Hemisphere (NH) temperature reconstruction (blue) and instrumental data (red) from AD 1000 to 1999, adapted from Mann et al. (1999). Smoother version of NH series (black), linear trend from AD 1000 to 1850 (purple-dashed) and two standard error limits (grey shaded) are shown. (7)
The accuracy of the ‘hockey stick’ type reconstruction shown above was essentially confirmed by The National Academies of America in 2006 with their paper ‘Surface temperature reconstructions for the past 2000 years.’ (8) (Also see additional information in Note 1 of Section 8)
The increasing power of computer reconstructions since MBH98 and 99 resulted in the more sophisticated ‘spaghetti graphs’ using multiple proxies, which somewhat modified the findings of the earlier hockey stick, but reinforced the notion of a world rapidly warming over the last century, in a manner unprecedented for at least a thousand years. This spaghetti graph comes from the IPCC working group 1 and illustrates twelve multi proxy reconstructions together with their locations, including mbh1999, which has instrumental temperature data added from 1902. (9)
Figure 5
So we have two competing climate history stories-one developed over a lifetime of academic research mostly before the computer era, and the other derived from a scientist using modern statistical techniques and the extensive use of novel proxies interpreted in a highly sophisticated manner using computers.
The ‘hockey stick’ and Lamb’s graph remain potent symbols to this day, and have created two vociferous climate camps, as the reconstructions seem to tell very different stories. The work of Dr Mann and his colleagues have been argued over numerous times during the last decade, but it is his findings that underpin current mainstream thinking on the nature of our climate during previous centuries. Basically his study found a generally stable climate for a thousand years that exhibited a slight decline in temperatures until around 1900 when the temperatures dramatically escalated. Mann’s research was thorough and interesting, and like Manley’s work with CET, and Hansen’s with global temperature, was a considerable feat of research and re-interpretation of existing knowledge, which until then had accepted considerable variability, with previous episodes of warming exceeding those in the modern era.
Of course we can’t know whether more information and the availability of powerful computer modelling would have changed Lamb’s findings, so it is primarily his view of historic climate we shall follow, to see if the material now available may have influenced his thinking and results for the period 1538 onwards, to a position somewhat closer to Dr Mann.
Section Two A brief examination of two differing versions of Climate History.
Towards the end of his long career, Lamb remarked that such elements as church and estate records, ships log books and a whole host of other historical records, now available in such places as the Met office archives, were only starting to become available. It is certain he would have found the enormous pool of information -observational and scientifically derived-now also available through the internet, to be a great help to his research.
Dr Mann often cited Hubert Lamb’s work; most notably for our purposes in figure 1 of his 2002 paper entitled ‘Medieval Climatic Optimum’ whereby reconstructions by the two scientists are usefully juxtaposed-Mann depicting the Northern Hemisphere- and Lamb, who used Central England records. (Note should also be taken of Figure 2 of this paper used by the IPCC, which show some differences.) (10)
In looking at the two versions-reproduced below in Figure 6 -we can readily see that the divergence between the two climate camps was caused by the two apparently radically different versions of climate history it gave.
Figure 6
In the Mann version of historic climate there is very limited variation either side of a mean anomaly, which gave rise to a limited MWP, generally substantially cooler than today, with gently declining temperatures throughout the period from 1400 to 1900, coupled with a lesser impact of the ‘Little Ice Age’ than had previously been accepted. Most controversial of all is the very dramatic uptick from the 1902 instrumental temperature records-the so called ‘hockey stick’. The information for this was derived from table 5 in MBH98 -later extended in MBH99- and adapted in the IPCC assessment. Figure 1a in MBH98 (linked to in reference 5 above) shows the geographic location of the proxies-mostly tree rings- but with some coral sediments, bore hole and ice core data, with land based instrumental records from 1902. There were a total of 24 proxy indicators back to 1450, with 22 multi proxy to 1400, there are also some 1100 temperature records from 1902 with the additional grid points in figure 1b providing SST’s back as far as 1854. The precise nature of the multi proxy data used in mbh98 is referenced here (11)
There was considerable controversy over Dr Mann’s reinterpretation of the size and extent of the MWP and LIA which we shall return to later, but as can be readily seen in Figure 6 his concept of climate history was at substantial variance with much of Lamb’s version, based on his 1965 CET work. (The extension of CET from 1965 to the year 2000 in the graph in Figure 6 appears to have been carried out by Dr Mann, not Hubert Lamb)
Lamb’s work showed substantially greater climate variability, with a distinct and warm MWP and two eras of the LIA-the second much more severe than the first, and a steadily climbing temperature from around 1690 to the present date , albeit with numerous statistically meaningful reverses and advances. Coupled with the long lived CET instrumental records, this appears to show that if the Mann reconstruction is correct, the British climate has at times varied substantially from that of the remainder of the Northern Hemisphere for 400 years or so.
We shall revert to the question of synchronicity and climate severity later in this paper, but it can be seen that even Lamb’s graph demonstrated modern ‘hockey stick’ characteristics (albeit it appears this data was later added by Dr Mann using CET) More intriguingly, Lamb shows another and much more dramatic ‘hockey stick’ just before the start of the 18th century-a period which seems to have aroused limited curiosity- and is the intended subject of a future article.
Dr Mann’s view that the climate had been relatively stable until man interfered with it in recent times, through excessive co2 emissions, became quickly accepted, as noted here by the UK Met office, a prime contributor through the Hadley centre to the IPCC assessments, who assert:
“Before the twentieth century, when man-made greenhouse gas emissions really took off, there was an underlying stability to global climate. The temperature varied from year to year, or decade to decade, but stayed within a certain range and averaged out to an approximately steady level.” (12)
The IPCC themselves say;
1 IPCC FAQ 6.2 Page114 of TAR4.
‘All published reconstructions find that temperatures were warm during medieval times, cooled to low values in the 16th 17th 18th 19th centuries, then warmed rapidly after that.’
These comments clearly refer to Dr Mann’s-rather than Hubert Lamb’s-version of climate events.
What we can determine with some certainty about the Little Ice Age (LIA), by looking at the available instrumental data and other records with the broader brush and sceptical eye they warrant, is that there were many anomalously cold periods which capture the episodic nature of the misleadingly named Little Ice Age. It is misleadingly named as the popular impression of unremitting cold for 400 years, when the Thames froze over each winter, is inaccurate. Although there were undoubtedly several long periods of intensely cold winters, particularly for much of the 17th century, with generally shorter recurrences through to the mid-19th century, the cold winters were punctuated by warmer ones, and there were many warm summers and other seasons similar to today, as noted here by the author. (13)
The term LIA was introduced into scientific literature by François E. Matthes as late as 1939 who subsequently believed the term ‘neo-glaciation’ was more accurate. (14)
We can trace much of the LIA through the medium of CET from 1659 (see figure 1) which captures some of the coldest episodes. This also usefully leads back to Hubert Lamb who used this and other English based records extensively.
Section Three What is CET?
It would be useful to clarify what CET is and isn’t, as it is a fundamental measure being used in this current reconstruction. The instrumental record itself dates from 1659. Our own reconstruction has been extended from this date back to 1538 by using a variety of historic records (not instrument readings) taken from the same geographic area. These are detailed in the separate paper ‘supplementary information,’ (linked to in Section 8 of this paper)
It is during this period that a notable divergence begins between the two versions of climate history (see Figure 6) as Lamb notes a descent into a second and severe episode of the LIA that Mann didn’t record as being especially significant. The period prior to 1538 is outside the scope of this present paper.
CET is not a single continuous set of instrumental temperature readings to 1659 but was the result of a project that sorted a mass of thermometer based temperature readings into a single coherent record covering a specific area of England, many years after the event. This notable achievement was carried out by Gordon Manley on behalf of the Met office. His 1953 paper describes in great detail how CET was assembled and the geographic area it covers. (15)
It is a fascinating piece of detective work carried out over a period of thirty years and was followed in 1974 by a further paper from the same author, which noted uncertainties and corrections, whilst commenting on the difficulties of trying to reconcile records due to the change from the Julian to Gregorian calendar- which occurred in 1752 in Britain making 11 days difference- but in different years in other countries. (16)
Manley’s work was expanded by Parker, so a number of variations of CET have been established over the years, as can be seen in this official description by Hadley/Met Office who maintain the figures.
“The CET dataset is the longest instrumental record of temperature in the world. The mean, minimum and maximum datasets are updated monthly, with data for a month usually available by the 5th of the next month. A provisional CET value for the current month is calculated on a daily basis. The mean daily data begins in 1772 and the mean monthly data in 1659. Mean maximum and minimum daily and monthly data are also available, beginning in 1878. These daily and monthly temperatures are representative of a roughly triangular area of the United Kingdom enclosed by Lancashire, London and Bristol. The monthly series, which begins in 1659, is the longest available instrumental record of temperature in the world. Manley (1953,1974) compiled most of the monthly series, covering 1659 to 1973. This data was updated to 1991 by Parker et al (1992), when they calculated the daily series. Both series are now kept up to date by the Climate Data Monitoring section of the Hadley Centre, Met Office. Since 1974 the data have been adjusted to allow for urban warming.”
The geographic triangular area described is a heavily populated area of the country. In a private email to the author the Met office described the amount of UHI as follows;
“The urbanisation corrections to the CET series have been applied since 1974. Initially they were just 0.1 degree C, in certain months, then gradually for more months of the year; from about 1995 onwards some of the corrections increased to 0.2 deg C, and by about 2002 all the corrections were 0.2 deg C.
The above applies to Mean CET. The urban heat island effect is much more noticeable for minimum temperatures than for maximum, so for the Minimum CET series the corrections are double those for Mean Temperature, whereas for Maximum Temperature it was deemed in fact that no correction was required.”
Due to its longevity CET is probably the most scrutinized instrumental data set in the world, which makes it especially valuable as a useful resource. As much of this paper is concerned with instrumental records deriving from thermometers it should be noted that in Chapter 5 of his book ’Climate History and the Modern World’, Lamb makes many good points about the relatively limited accuracy of instrumental records. As observed in my own article on the same subject, at best we can believe in the general direction of travel of the local instrumental record-especially when backed by such things as crop records/ observations-but not in their accuracy to tenths of a degree (17)
‘Global’ records are much less reliable than local ones due to the manner in which they are assembled, and the reality of a meaningful single global temperature is the subject of much debate, as observed by French climatologist Marcel Leroux. ‘Yet, they know very well that there is not one “global” climate, but a large variety of climates, depending on latitude, geographic conditions, and atmospheric dynamics.’ (18)
Brown and Jones commented on the many instances of local cooling trends, seemingly recording different- and cooling- climates to that observed in the global – and warming- record (19)
The Berkeley earth surface temperature project ( BEST) also confirm that one third of the Globes weather stations show a cooling, not warming, signal again demonstrating that no single global climate prevails. (20)
Consequently Leroux’s comments seem a reasonable premise, and the attempt to find a warming signal in every piece of data somewhat counter-productive.
As a result of the various studies into CET referred to above, two sets of official temperature data relating to it are generally available. Hadley/Met office themselves tend to use the data to 1772 whilst this study has used the longer official figures to present the data to 1659 in a similar format. It is reproduced again at this point (Figure 7) as a useful springboard for further comment. In this context schematic diagrams, such as those already used in Figures 2 and 3, can be seen to be useful in providing a simplified view of extended timescales. However they are unable to show the enormous variability from month to month and year to year that is a feature of the British weather. This annual variability can be readily seen below, although the eye might be first drawn to the red trend line.
Figure 7 Hadley 1659 in the style of Hadley 1772
In his graph (used within Figure 6) Lamb records considerable temperature variation with a decline from 1400, then a rise after 1500, with a further decline to the early 1600’s but with the coldest point in the late 1600’s. The abrupt dip towards the end of the 17th Century and the astonishing recovery immediately after, lasting towards the middle of the following century, can be clearly seen in CET as perhaps the most notable feature of the entire record.
Clearly this period of some 250 years, commencing 1500, is critical in understanding the influences on our climate, being centuries before the impact of man-made co2 become a serious issue. Referenced here is the official Cdiac data to 1750 showing the trivial emissions at the start date. (21)
Section Four-Reconstruction of the period 1538 to 1659
The accuracy of the proxies, such as tree rings and bore hole material, used by MBH in their reconstruction are dealt with later in this paper in relation to the findings of both this reconstruction and that of Hubert Lamb.
Our reconstruction, in order to identify the start of the warming trend, centres on the period 1538 to 1659. It was this latter date when the CET instrumental records began, and we can usefully bookend this era with two pieces of observational climate information.
A brief breakdown in the cold winter trend in Britain was recorded in the diary entry of Samuel Pepys for January 1660/61-the year the Royal Society was established- when he wrote;
“It is strange what weather we have had all this winter; no cold at all; but the ways are dusty, and the flyes fly up and down, and the rose-bushes are full of leaves, such a time of the year as was never known in this world before here.” (22)
So here we can see that Pepys (born February 1633) had been living through a long period when cold winters had become the norm. We can take with a pinch of salt ‘as was never known in this word before here’ as people often tend to base such beliefs on their personal experiences, and as shall be seen in the research material there are numerous similar claims from other observers.
Summers could still be hot. Pepys noted that 1661 and 1665 were particularly warm, and more especially during 1666 when the UK had an extremely hot dry summer-said to be the warmest in living memory- that was brought on by a blocking high pressure system over Scandinavia. The dry North easterlies helped spread the devastating Great Fire of London in 1666. The following winter, however was so cold that the great oak trees of the English Midlands split. (Humidity has a great part to play in temperatures)
We can usefully roughly date the initial down turn by turning to 1560 when the Rev Schaller, pastor of Strendal in the Prussian Alps wrote;
“There is no real constant sunshine neither a steady winter nor summer, the earth’s crops and produce do not ripen, are no longer as healthy as they were in bygone years. The fruitfulness of all creatures and of the world as a whole is receding, fields and grounds have tired from bearing fruits and even become impoverished, thereby giving rise to the increase of prices and famine, as is heard in towns and villages from the whining and lamenting among the farmers.”
That this appeared to be the start of a trend comes from this comment by John King, an Elizabethan preacher from Britain who wrote in 1595;
“Our years are turned upside down; our summers are no summers; our harvests are no harvests!”
It is useful to note here that it is inclement summers being complained of, and this juxtaposition of intensely cold and intensely warm spells-although by no means annual events- seems to be a notable feature of this period.
The decline in the climate is reinforced by this account from 1610 when John Taylor, talking of the hills around him in Deeside Scotland, remarked that “the oldest men alive never saw but snow on the top of divers of these hills both in summer as in winter.”
(The 1560 and 1610 quotes from the book ‘The Little Ice Age’ by Brian Fagan)
Our apparent modern amnesia regarding previous climatic conditions can be seen to be nothing new by reading the comments from the annals of Dunfermline Scotland from 1733/4, when it was recorded that wheat was first grown in the district in 1733. Lamb wryly observes that was not correct, as enough wheat had been grown further north in the early 1500′s to sustain an export trade.
This information also confirms a warm period in the early 1500’s to one that had changed to a cold period by the time of Pastor Schaller commenting in 1560.
We can find another comment usefully topping and tailing our period of interest here;
“During the long cold spell between 1559 and 1652, average heights in Europe declined by 0.8 inches. That disastrous period in European history is referred to by historians as the General Crisis of the 16th Century. It was a time of starvation and deadly conflict, including the brutal Thirty Years War.” (23)
There are various other records available relating to the 1500’s and 1600’s from a study entitled ‘Evidence for the climate during the Late Maunder Minimum from proxy data and model simulations available within KIHZ’ (24)
The above link has some useful graphs of likely temperatures from 1500 onwards, although it is mainly concerned with the period from 1680 on.
The following study on solar activity uses research by Groveman and Landsberg, who in 1979 reconstructed Northern Hemisphere temperatures from 1570 to 1860- (the remainder of the graph period is a composite study by Jones et al made in 1986 and 1988) (25)
Figure 8
The 1997 book ‘Climate of the British Isles’ edited by Mike Hulme and Elaine Barrow (page 188) has a graph showing a temperature peak around 1550 followed by a very sharp decline straddling the beginning of the 17th century. (26)
Further evidence of the changing climate can be gathered from this unlikely source;
‘From 1564 to the 1730s—the coldest period of the Little Ice Age—malaria was an important cause of illness and death in several parts of England. Transmission began to decline only in the 19th century, when the present warming trend was well under way.’
‘From; Shakespeare to Defoe: Malaria in England in the Little Ice Age’ (27)
1564 has a special significance as can be seen here;
Figure 9. Hunters in the Snow by the Flemish painter Pieter Bruegel the Elder (1525–1569).
Completed in February 1565, during the first of the many bitter winters of the Little Ice Age. Bruegel painted at least seven such snow scenes. (28)
An even more unlikely source of information comes from this study of witchcraft trials, events possibly precipitated by superstition of changes in climate which subsequently impacted on the economy of the time. Written by Harvard economics PhD Emily Oster it is entitled ‘Witchcraft, Weather and Economic Growth in Renaissance Europe ‘ and published in Journal of Economic Perspectives in 2004. This is included as it covers our period of interest-especially figure 1- and also provides some intriguing and little seen sources of references. (29)
Dr Pfister reported to Hubert Lamb that for several decades prior to 1564 the Swiss climate was on average 0 .4c warmer than today (1990’s) In Switzerland, the first particularly cold winters appear to have begun in the 1560s, with cold springs beginning around 1568, and with 1573 the first unusually cold summer (Pfister, 1995).
Dr Pfister has an interesting graph of central Europe temperatures showing a progressive cooling of winters from the 1540’s, a subsequent recovery around the 1620’s, with another deterioration in the 1690’s (Fig 76 Lamb– Climate History and the Modern World.)
The following extract is from ‘The Little Ice Age’ by Brian Fagan;
“It was not only the cold that was a problem during the Little Ice Age. Throughout Europe, the years 1560-1600 were cooler and stormier, with late wine harvests and considerably stronger winds than those of the 20th Century. Storm activity increased by 85% in the second half of the 16th Century and the incidence of severe storms rose by 400%. “
There are many other references dating from this period available from the Alps: records of advancing snow and ice burying silver and gold mines, alpine villages, farms and pastures being abandoned due to colder climate, even physical evidence recovered today under retreating glaciers.
There are also the German chronicles of devastation, cold and starvation from the period before and during the Thirty Years War. These are discussed in the book, “Power, violence and mass death in pre-modern and modern times” by Joseph Canning, Hartmut Lehmann and J.M. Winter (pp.94-95) (29a)
“For the constitutive paradigm of the “Little Ice Age”, matters of power, violence and death depended on a fundamental change of climate. To be sure, in the 1570s the average temperature fell by only a few degrees, and equally certain, after the 1570s we can observe periods of remarkably stable, warm weather. However, as Christian Pfister and others have shown, after 1570 and continuing for more than a century and a half, these stable conditions were the exception, not the rule. What the people of Europe were forced to experience after the 1570s were long, cold winters, the late arrival of spring, cold, wet summers, and an early winter. In sum, weather conditions in the growing seasons of agricultural products tended to become too short causing the produce – if any grew at all – often to be of poor quality. Ensuing food shortages triggered an avalanche of reactions: while some people turned to God, confessing their sins and imploring God to grant the food necessary for survival, others hunted witches whom they considered to be agents of the devil and whom they held responsible for the failed harvests. As a result of malnutrition, illnesses of all kinds spread rapidly, including the plague. Thus long before the outbreak of the Thirty Years War, population began to decline in many European countries.”
Brian Fagan noted that Glaciers in the Alps advanced significantly between 1600 and 1610 again from 1690 to 1700 and around 1820 and 1850 and that there had already been some movement from around 1546. There seemed to be some retreat around 1563 for a decade, but 1670 saw the Maximum advance in the Eastern Alps, which started retreating again around 1712.
A downturn in climate between 1560 and 1610 in Spain is noted here; (30)
There is an especially good graph by Prof. G. Patzelt who has reconstructed the declining summer temperatures in the Alps some 7000 years back in history (30a)
(Note; Prof Patzelt of the University of Innsbruck has been a noted glaciologist for many years. This graph was part of a presentation to controversial climate group Eike, but the venue should not detract from the science and reputation of the Professor)
Another study by Patzelt below, on forests, glaciers and temperature anomalies, shows how the tree line rose and fell over time: (30b)
An additional study by him from 2008; (30c)
“An Gletscherrändern werden immer wieder Holzreste freigelegt bzw. ausgespült. Sie deuten darauf hin, dass es in den letzten 10.000 Jahren häufig wärmer als heute gewesen ist.”
Translation; “Pieces of wood are found repeatedly at the edges of receding glaciers. These provide evidence that it was frequently warmer than today over much of the past 10,000 years.”
That Glacier advance is thought to have begun around 1560 and reached their maximum around 1740 is noted here; (31)
In the Andes it was similar ‘ The LIA maximum advance occurred between cal. yr 1550 and 1720 AD, and a re-advance occurred around cal. yr 1830 AD.’ (32)
In Alaska; “The Little Ice Age reached its maximum extent here about 1750, when general melting began.” (33)
The following gives a useful summary of notable glacier advances and retreats that began around 1560 and had generally reached its maximum by around 1750 or earlier; (34)
Gordon Manley made the interesting observation that glacier advances took place in periods of cooler summer and springs, rather than cold winters. (Or presumably a combination of consecutive cool summer and cold winters) (35)
This recent study also seems to illustrate an upwards trend in temperature from the early part of the 17th century- figure 5 (36)
This graph derived from ice break up times in Talinn shows an increasing temperature trend from 1500 (See page 195 and 197) (36a)
This reconstruction by Craig Loehle also demonstrates a rising temperature trend to the present day starting from a trough in the early 1600’s ( 36b)
Figure 103 in Hubert Lamb’s ‘Climate History and the Modern World’ shows an estimate of the growing season near the upper limit of cultivation in Scotland which mirrors much of the glacial record and demonstrates a steady-but not constant-improvement after a modest peak in the mid 1550’s- from the trough of the early 1600’s to the present day.
The previous examples demonstrated temperature generalities over decades, rather than year on year specifics for the CET area. It has identified a widespread change in the climate dating from a peak reached around 1550 with a subsequent decline to a low point around 1607, that was the precursor of a sporadic period of intense cold throughout much of the 17th century, with the coldest decade of all being the 1690’s which was the subsequent genesis of a long slow warming trend towards the present day.
The purpose of this study is to extend the CET record from 1659 to 1538 and identify any correlation between scientifically determined events and those observed from historical observations and records. It is clearly pointless documenting here thousands of examples of specific records and contemporary observations during this period that relate to the geographic area CET covers, as it would make this document extremely unwieldy. Consequently all the research from online sources, reference books and that gathered by the authors personal research at the archives of the Met office are detailed in chronological order in the paper found on the link here ‘Supplementary information’ together with the criteria, assumptions and references that were used to create the reconstruction;
Long slow thaw supplementary information
Section Five The reconstruction to 1538 and its interpretation
The interpretation of the data detailed in ‘Supplementary information’ is shown here in the form of a graphic reconstruction of each year between 1538 to 1659 showing actual likely temperatures. The warm spell centred on the 1630’s is of most note.
Figure 10
The context of the reconstructed temperatures from 1538 in relation to the instrumental CET record from 1659 can be seen in this graph below in the style of Hadley 1772-which is shown as temperature anomalies.
Figure 11
In Figure 11 we can detect the peak of the warm period around 1540 that Lamb observed in Figure 6. From this high point there was then a notable initial decline, as observed by Pastor Schiller in 1560, and its continuation, observed by John King in 1595, so that during the first decade of the 17th century cold was the norm, as observed by John Taylor of Deeside in 1610 and confirmed by glacier records. By Taylor’s decade the climate had already reached lower values than during the cold trough noted by Lamb a century earlier, and indeed was colder than the 500 years that preceded it (if Lambs reconstruction of the period preceding 1538 in Fig 6 is accurate )
The start of the 17th century had a substantial number of bitter winters, especially notable was 1607/8 which was one of the coldest in the entire 475 year extended CET record, but that first decade was somewhat balanced by some notably warm summers.
The period from the start of the ‘Bruegel’ winters from around 1564 to around 1620 appears to be probably the second coldest extended period in the record-but somewhat behind the decades commencing 1670. The notable warm bump around 1630 to around 1670 confirm the upwards trend we could note at the very start of the instrumental record in 1659, as shown in Figure 1, as the cold winters of that period were again ameliorated by some notably warm summers. This warm bump seems to be of equal value to the one around 1730 that Lamb observed, and like that period warrants further investigation in a future paper.
It appears therefore that the instrumental record did capture the coldest period of the LIA.
In the graph below (figure 12) showing ‘real’ temperatures rather than anomalies, the reconstruction from historic records is shown in green, instrumental records in red.
Because of the notably warm period at the start of the reconstruction and around the 1630’s, the green trend line to the present day is virtually flat. The red trend line illustrates that it is probably more accurate to describe the warming trend as commencing around 1660 rather than earlier. (The red line extension to 1538 is purely an artifice of Excel)
Figure 12
In this graph below (figure 13 ) showing the 10 year moving average, the low point is clearly the 1690’s with the very earliest part of the graph potentially around as warm as the modern era. This study also highlights the profound effect of the 40 year cold period around the 1690’s to 1710 and in particular the decade of the 1690’s.
Figure 13
The modern era is potentially showing the effects of needing a uhi adjustment greater than the Met office currently apply. However, as we had earlier observed that instrumental records should not be considered accurate to tenths of a degree we are perhaps splitting hairs. Consequently, more accurately we should observe that the ‘direction of travel’ of temperatures, when combined and constrained by historic records, shows that at several points from 1538 there are similarities to the modern era as regards warm periods.
This was a little unexpected as the authors assumption had been that only the MWP itself would rival modern temperatures, and that with a long rising trend the warmest years would tend to cluster at the end of the record, rather than along its way. However this illustrates the great variability in our climate and that there appears to be some sort of natural cycle whereby notable peaks and troughs can be identified at irregular intervals. The context can be seen by noting that despite the great variability that can be observed throughout the record, the British climate operates within a relatively small mean average temperature as can be seen in Figure 14 and the ‘hockey stick’ type effect from around 1900 can not be observed at all.
Figure 14
Below is a chart using all available databases, Berkeley, Giss Hadley/Cru etc. to the start of the CET instrumental record in 1659;
Figure 15
It appears to demonstrate that the new Berkeley dataset is a reasonable match to CET and continues the series of peaks and troughs that can be observed in older instrumental records such as CET.
The graph below takes all available global data sets plus the ‘Hockey stick’ data (in black) used in the third IPCC assessment of 2001 and combines it with the extended CET reconstruction to 1538
Figure 15a
It should be noted that the vertical lines at the start of the BEST data and Hadcrut3 are merely a feature of the graphing package which note that the record started at that point. The BEST data in the period 1800 to 1830 appears to be somewhat exaggerated and perhaps reflect the very small numbers of stations being sampled rather than a real global climate state. Other than this, the instrumental CET record matches the instrumental global record quite well.
The research phase for the reconstruction of CET to 1538 has, as far as possible, tried to concern itself with the CET geographic area in order to compare like for like with the instrumental record. From looking at the graphs above and the joint graph reproduced again below as figure 16 we can make some observations
Figure 16
We can repeat our earlier observation that CET instrumental to 1659-this time augmented by the reconstruction using historical records to 1538, demonstrates a temperature profile that looks quite different to significant periods of the remainder of the Northern Hemisphere if the official version of extended climate-as epitomised by the ‘Hockey stick’- is taken as the appropriate set of data which it should be measured against.
Similarly the other extended instrumental records of this time –from cities-which illustrates a general warming trend throughout much of their history, incorporated within this article referenced below, may also not be representative of the general NH extended cooling trend that Dr Mann identified as lasting for 900 years until the start of the 20th Century. (37)
An alternative explanation is that the reconstructions and instrumental global data sets in fig 15a together with those city ones mentioned in (37) do in fact accurately represent the prevailing climates of the time, and therefore it is ‘the hockey stick’ that is not a reliable representation. In unravelling the accuracy of any of the reconstructions, it is reasonable to try to determine if it is CET, together with the other records, or the Hockey stick, which is anomalous, by posing two interlinked questions. The first is to ask what evidence there is for the notable divergence of the various data sets -Lamb and this 1538 reconstruction on the one hand- and MBH 98/MBH99 on the other. To explore this it is useful to also ask if CET merely represents a specific area of central England or if it has a wider geographical application, as this impinges on the reality or not of a widespread and severe LIA.
Section 6 Can CET represent a wider geographic area and establish the existence of a Hemispherically significant cooling period?
According to our reconstruction from 1538 the first major trough was reached around 1607 (Figure 11) It can be seen as descending from a peak attained by 1560, following a century long broadly warming period (according to Lamb) that punctuated the LIA into two parts, a relatively short period following the end of the MWP, and another following a return to periods of bitter cold weather at the start of the 17th century that is confirmed both in this reconstruction and that by Lamb.
The divergence in the Mann/Lamb graphs (Figure 16) at this point is due to the considerable differences in the interpretation of the extent and warmth and extent of the MWP (outside our period of study) and the cold and extent of the LIA.
Contrary to popular belief Dr Mann didn’t refute the existence of either a MWP or LIA but thought of them as having a limited geographic impact. His 2002 article ‘Medieval Climatic Optimum’ amplifying his research on the MWP-one of the most controversial aspects of his reconstruction- is linked below (38)
He saw the MWP (covering a warm period predating the subject of this paper) as primarily a North Atlantic and adjacent regions anomaly (including part of Europe) and not a synchronous world-wide event, and that overall the Medieval warm period was substantially less warm than the two most recent decades, which he believed to be more global in its extent. Dr Mann also believed that the LIA was primarily a European matter from the 16th to mid-19th centuries due to solar variations, co-authoring a paper entitled ‘Solar Forcing of Regional Climate Change during the Maunder Minimum’ published in ‘Science’ in December 2001, that took a detailed look at this cold period.
“These results provide evidence that relatively small solar forcing may play a significant role in century-scale NH winter climate change. This suggests that colder winter temperatures over the NH continents during portions of the 15th through the 17th centuries (sometimes called the Little Ice Age) and warmer temperatures during the 12th through 14th centuries (the putative Medieval Warm Period) may have been influenced by long term solar variations.” (39)
His paper from 2002 entitled ‘The Little Ice Age’ comments; (40)
“If defined as a large-scale event, the Little Ice Age must instead be considered a time of modest cooling of the Northern Hemisphere, with temperatures dropping by about 0.6 C during the 15th–19th centuries (Bradley and Jones, 1993; Jones et al., 1998; Mann et al.,1998, 1999).”
And;
“The Little Ice Age may have been more significant in terms of increased variability of the climate, rather than changes in the average climate itself. The most dramatic climate extremes were less associated with prolonged multiyear periods of cold than with year to year temperature changes, or even particularly prominent individual cold spells, and these events were often quite specific to particular seasons. While the 17th century appears to represent the timing of peak cooling in Europe, the 19th century was more clearly the period of peak cold in North America (panel b).”
His 2009 co-authored paper;
‘Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly’ goes into considerable detail on both topics with numerous graphics. (41)
It was reviewed by Skeptical Science who made these comments;
“The Medieval period is found to display warmth that matches or exceeds that of the past decade in some regions, but which falls well below recent levels globally. This period is marked by a tendency for La Niña–like conditions in the tropical Pacific. The coldest temperatures of the Little Ice Age are observed over the interval 1400 to 1700 C.E., with greatest cooling over the extratropical Northern Hemisphere continents. The patterns of temperature change imply dynamical responses of climate to natural radiative forcing changes involving El Niño and the North Atlantic Oscillation–Arctic Oscillation.”
And;
“Some regional warming greater than today, some regional cooling, over all no global warming comparable to today”. (42)
Dr Mann was possibly under the impression that Hubert Lamb himself did not believe that the records he accumulated had any especial relevance beyond a relatively narrow geographic area as regards the existence of the MWP
“Indeed, when Lamb (1965) coined the term Medieval Warm Epoch, it was based on evidence largely from Europe and parts of North America.
AND
“Although Lamb (1965) did not argue for a globally synchronous warm period, his characterization has often been taken out of context, and used to argue for global scale warmth during the early centuries of the millennium comparable to or greater than that of the latter 20th century”
Both comments from this 2002 document (43)
This interpretation is not strictly correct as Lamb believed CET (and other reliable records) had a much wider relevance beyond that of the central portion of England. He observed in Chapter 5 of ‘Climate History and the Modern World’;
’…that the last centuries (CET) records ‘have been highly significantly correlated with the best estimates of the averages for the whole Northern Hemisphere and for the whole earth ‘
In Table 4 page 281 of his book Lamb explores the correlations he had established. (44)
He further commented;
‘…over the 100 years since 1870 the successive five year values of average temperatures in England have been highly significantly correlated with the best estimates of the averages for the whole Northern Hemisphere and for the whole earth’ (In this last comment he is no doubt referring to his work at CRU where global surface records back to 1860 or so were eventually gathered) he continued; ‘they probably mean that over the last three centuries the CET temperatures provide a reasonable indication of the tendency of the global climatic regime.’
‘Tendency’ is a very good word and is preferable to ‘preciseness’ which has become an integral part of the climate science lexicon.
Writing about tree rings in the same chapter (this was of course many years before Mann’s 1998 reconstruction made extensive use of this proxy) Lamb commented on the University of Arizona ‘Laboratory of Tree Ring Research’ (who Mann collaborated with for his later study) concerning bristlecone pine trees in the White Mountains. ‘…this long series at the upper tree line essentially registers summer temperatures. It is of interest that from AD800 to the present century (20th) its hundred year averages are correlated in a statistically significant degree, with the temperature derived for central England.’
Coming closer towards the modern era this paper ‘British Winters in relation to World Weather’ written by E W Bliss and published in 1926 by the Royal Meteorological Society provides a scholarly examination of the relationships discovered, which gives us an insight into what was happening elsewhere in the world. This portion from the summary is intriguing;
“The results indicate that conditions in the Southern Hemisphere play a part comparable with that of the North Atlantic oscillation in controlling subsequent winter weather in the British Isles.” (45)
In the 1997 book ‘Climate of the British Isles’ edited by Mike Hulme and Elaine Barrow (previously referenced) the authors distill a great deal of information from such luminaries as Phil Jones (a successor to Hubert Lamb at CRU) (46)
‘An examination is made of the correlation between the British isles and Northern Hemisphere. The CET series is related to average land temperatures over the Northern Hemisphere, but probably no more than would be expected from any other region of comparable size in the hemisphere. The relationship appears to strengthen when temperatures are averaged over decades or more but considerable caution should be exercised in extrapolating trends from the long CET record to the hemisphere as a whole.’
This comment below from Physics World quotes an academic study by Mike Lockwood of the University of Reading (47)
‘Comparing the changes in English temperatures (which the researchers say are representative of European temperatures as a whole) with fluctuations in solar activity, the researchers found a strong correlation.’
A further reference from Mike Hulme in his paper “Sensitivity to Climatic and other factors”
‘The Central England Temperature is perhaps the single most important and representative measure of the surface climate of the UK. It is also quite well correlated with land temperatures over the entire Northern Hemisphere. At an annual level this correlation is about 0.4, but when average values over 10-year periods are compared this correlation rises to about 0.75.” (48)
Geert Jan van Oldenborgh of KNMI makes the following comment;
‘…like most temperature records in Northwest Europe the Cet time series over the 20th century shows a striking similarity with the world average.’ (49)
In this study by Phil Jones and Michael Mann Figure 2 demonstrates that CET is a good proxy for much of the time for the Northern Hemisphere (49a)
In the study referenced below CET trends are overlaid on to some of the oldest instrumental records available, and graphically demonstrate that there is considerable correlation in data sets as diverse as New York City to Geneva (50)
We must be cautious in believing that any single instrumental record can act as a reliable proxy for the entire world as was observed here; (51)
“One drawback of local records is that they tend to show much larger scatter than global/hemispheric averages.” Compared to global, hemispheric, or even regional averages, the noise level in individual station records is huge. You can’t expect to be able to “see” what the long-term behavior is just by looking at graphs of individual station data, especially with trend-squashing y-axis scales. Hopefully an examination of a location over several hundred years will enable us to cut out the noise and hear the message underneath it.”
However, the extensive material available tends to provide support for the notion that the English temperature history and records presented in Fig 30 of Chapter 5 of ‘Climate History and the Modern World’- which appears to be the basis on which the IPCC subsequently produced their global graph in 1990-does perhaps have some wider significance that usefully illustrates general trends, especially in Europe and the North Atlantic, and arguably much further afield. The importance of CET as a broader temperature proxy is further enhanced by its longevity and the scrutiny it has subsequently received by academics because of this.
Figure 17 IPCC 1990 view of Climate derived From Lamb
The CET records, especially when coupled with other instrumental and observed records, appear to show that there is considerable divergence at times from the Mann Northern Hemisphere reconstruction seen in Figure 4. Why should that be?
An indication of the reasons can be gained by referring to Figure 5 and reference (11) which together shows the nature and location of proxies used by MBH98 amongst others.
Previous critiques of MBH98 and 99 tended to focus on the quality of some of the proxies used, or their highly complex interpretation. Few seem to focus on their appropriateness as the means of creating a temperature anomaly accurate to fractions of a degree dating to 1400AD and 1000AD respectively.
The studies used a substantial number of Sea surface temperature records as one of its data set series. Obtaining a SST depended heavily, for much of its history, on buckets being thrown over a ship at varying depths to collect water samples. That this is not a reliable way to determine precise global ocean temperatures back to the middle of the 19th Century was observed here; (52)
The largest number of proxies used to reconstruct temperatures were derived from tree rings. These have a number of problems. Some of the complexities are paraphrased from Loehle, C. 2009. A Mathematical Analysis of the Divergence Problem in Dendroclimatology. Climatic Change 94:233-245
‘…..in some species the tree may be responding to last year’s temperatures because they set buds in the fall. In masting species, growth following a mast year will be poor, and also that over long periods a single tree is affected by the death and growth of neighbours and growth is correlated with local rainfall. Many studies typically use ring width when they should be using basal area increment, which tends to be linear over the life of the adult tree (past the pole stage.”
Trees can only ‘record’ information during the growing season and growth is greatly affected by moisture, night/day temperature differential, day length and light intensity which includes the degree of shading from other trees. Prof Steve Wofsy of Harvard University says even a passing cloud can affect photosynthesis and growth. There are thus many local variables and information is subsequently extracted by the use of highly complex and controversial statistical analysis. Under all these circumstances it is somewhat perplexing as to why such proxies have come to be viewed as a reliable means of recording the equivalent of an annual mean temperature accurate to fractions of a degree, from which it is possible to reconstruct one thousand year old climate scenarios
This potential inaccuracy can be seen in the very large error bars of such studies as the hockey stick (figure 4) of well over a degree.
Tree rings have been used to record basic information such as moisture since the 1780’s but extracting precise and highly detailed information would appear to be outside the scope of our present levels of knowledge. This from the Paleontological Research Institution gives a useful and even handed primer on using tree rings in climate research. (53)
It would be misleading to give the impression that those involved in climate science are unaware of the limitations of historical documentary evidence (so called ‘anecdotal’ material) or the potential shortcomings of proxies such as tree rings. These very subjects are dealt with in section 2.2 and 2.3 respectively of the 2004 article “Climate over Past Millenia” by Jones and Mann (reviews of Geophysics, 42, RG2002/2004 (53a)
The very pertinent comment is made that; “Inferences from regional data in isolation will clearly provide a biased view of larger-scale changes.” (Which is of course why this paper has tried to establish if CET has any meaning outside of Central England.) Jones and Mann provide several examples of historic documentary evidence that they believe has too much emphasis placed on them, including vineyards in medieval England-pointing out there are far more today than there were then- and commenting on the frequency of Frost fairs. In the case of the latter example they refer to Lamb (1977) who noted such events only occurred 22 times between 1408 and 1814 and eventually ceased due to the rebuilding of London Bridge, not necessarily because the winters became too warm to facilitate them.
‘The Long Slow Thaw’ has dwelt much on the LIA as it covers such a key part of this reconstruction and also made reference to the MWP, although it is outside this papers time scale . Section 6 of ‘Climate over past Millennia’ is entitled “ FUTURE DIRECTIONS: WHERE DO WE GO FROM HERE?’ And what is written there is therefore of especial interest;
“[97] Section 4 indicates that the broadest features of the ‘‘so-called’’ MWP and LIA can be seen in the reconstructions of large-scale mean temperature variations over the past millennium, but such reconstructions show considerably greater detail that defies the use of these simplistic terms.”
And
“As the detail of our knowledge improves, the ‘‘MWP’’ and ‘‘LIA’’ are increasingly likely to be regarded as overly restrictive terms…. In the instrumental period, warming in the 20th century is generally qualified as occurring during the early to middle and/or the later decades [Jones and Moberg, 2003]. This interpretation is only possible with hemispheric and global average series and would be impossible to determine from series at local or regional scales. In a similar vein the climate of the recent two millennia at the largest of scales can only be described using composite series of the type displayed in Figure 5. “
And
“[98] Likely expansion and improvements in the network of available proxy series will increasingly in coming years lead to viewing the restrictive terms such as the MWP and
LIA as obsolete. We anticipate the field of paleoclimatology moving toward data sets that can be used to develop spatial maps (with associated errors) for each season of the last one to two millennia, using techniques that can easily accommodate continual revision to our best available estimates as new series are developed. Particularly at regional scales, such revisions will arise from the addition of specific new high-quality proxy series.”
The paper recommends the phasing out of such ’restrictive’ terms as the MWP and LIA and ‘instead refer to anomalous climate periods by calendar dates, as is the practice in the description of more modern climate changes.’
In my article I have suggested the LIA is ‘misnamed’ so have no real problem with the reasoning, other than it has become a familiar and well understood term to describe the various periods of cold that can be observed over several hundred years and the alternatives suggested seem to minimise the importance of the periods.
‘Climate over Past Millennia’ is an interesting and detailed paper dealing with many aspects of the building blocks of our changing climate. In it are expressed some of the uncertainties and unknowns that are seldom mentioned in IPCC documents. it is well worth a read but does brings us back to whether CET can be more generally applied to the Northern hemisphere rather than being perceived as representing a small geographic area, and also if it has any broader lessons in, for example, identifying the dates, severity and synchronicity of LIA periods.
The evidence on both counts-from a wide variety of scientific and observational sources- seems to strongly suggest that it can.
Section 7 Conclusions and Postscript
Conclusions;
1) CET seems to be a reasonable-but not infallible- proxy for the Northern Hemisphere. Britain has a maritime temperate climate, so whilst it can usefully indicate wider trends it will not generally follow the extreme peaks and troughs of more climatically volatile regions. The moderate nature of the British Climate marks out the deep troughs of the LIA, observed around 1690 and various other periods, as extraordinary.
2) CET matches well for much of the time with ‘global’ data sets (although the value or accuracy of a global record remains open to question). If instrumental CET is corroborated by global sets from their inception around 1850s it is reasonable to suggest that CET will also correctly portray the predominant climate since its own inception in 1659.
3) Any attempt to construct a single global or even Northern Hemisphere temperature covering many centuries will encounter substantial difficulties, as incomplete information from novel proxies will probably not adequately represent the extremes that are experienced at either end of the temperature spectrum, so what is considered the ‘average’ is possibly representative of no climate state that actually ever existed. Considerable uncertainties abound in virtually every area of historic temperature reconstruction-including this one- and the ‘error’ bars are very broad. In the case of ‘1538’ plus or minus half a degree Centigrade.The existence of the UHI effect in many instrumental records confuses data even further and the allowance for this factor in recent decades is probably insufficient.
4) The nature of the proxies used in MBH98 and 99 have inherent problems and have proved very controversial. Tree rings have an inability to adequately represent the conditions of the entire year, amongst other difficulties, whilst SST’s have their own considerable shortcomings. Mixing proxies also causes their own problems. Taken in total, the data used in such studies is unlikely to accurately represent the climates prevailing at the time back to 1400AD and 1000AD. Carrying out complex statistical analysis on questionable data does not render the initial data any more meaningful as a scientific measure. Paleo reconstructions as a whole should be treated with caution when it relates to precise representations of temperature.
5) Lamb gathered together a variety of forms of evidence in his reconstruction. The schematic of composite graphs seen in figure 16 and 17 -when compared to the reconstruction to 1538- seems to confirm with other research that Lamb’s view of climate history was broadly correct. The main caveats we would place is that our own 1538 reconstruction seems to indicate slightly warmer humps around 1550 and 1630 than Lamb notes. This needs to be checked as it was unexpected
6) The hockey stick remains a potent icon to this day. However the gradual decline in temperatures over the centuries that it depicts cannot be detected, nor the lack of variability of the climate over the same time scales. The sharp uptick in temperatures from the start of the 20Th Century is a likely artifact of computer modeling through over complex statistical interpretation of inadequate proxies. Modern warming needs to be put into its historic context with the patterns of considerable natural climatic variability that can be observed from the past.
7) The available information seems to demonstrate that there is a long established warming trend dating back some 350 years to 1660-with various notable trends within the trend.
8) When viewed from a 1538 perspective the warming trend becomes imperceptible. That period seems to have been around as warm as today and there are others that also seem to exhibit notable warmth to levels not dissimilar to today’s. This finding was unexpected and warrants further research.
9) The Met office assertions of a virtually unchanging climate until the last century does not seem to be supported by the wealth of information available in their own archives, some of which is detailed in the document ‘supplementary information’.
10) The 1538 reconstruction will be updated as further evidence becomes available. In particular we need to assess the subjectivity of written records whereby one chroniclers ‘excessive heat’ may be someone else’s ‘pleasantly warm’.
Postscript.
In his book ‘The Little Ice Age’ Professor Brian Fagan notes;
“The little ice age of 1300 to about 1850 is part of a much longer sequence of short term changes from colder to warmer and back again which began millennia earlier. The harsh cold of the LIA winters live on in artistic masterpieces….(such as) Peter Breughel the elders ‘hunters in the snow’ (see Figure 9) painted during the first great winter of the LIA but there was much more to the LIA than freezing cold and it was framed by two distinctly warmer periods. A modern day European transported to the heights of the LIA would not find the climate very different even if winters were sometimes colder than today and summers very warm on occasion too. There was never a monolithic deep freeze rather a climatic see saw that swung constantly back and forwards in volatile and sometimes disastrous shifts. There were arctic winters, blazing summers, serious droughts, torrential rain years, often bountiful harvests and long periods of mild winters and warm summers. Cycles of excessive cold and unusual rainfall could last a decade a few years or just a single season. The pendulum of climate change rarely paused for more than a generation.”
Having examined tens of thousands of accounts of the weather from 1500-1750-for this article, through books, online and also during several days research in the Met office archives in Exeter, Fagan’s account resonated with me. Being so dependent on the land and the successful raising of crops made our ancestors acutely aware of the weather and of climatic trends, and their accounts are often highly detailed.
Reading their vivid testimony of the seasons – sometimes in books several hundred years old- was like viewing their lives in a speeded up film.
First, a disastrously cold winter threatened their existence- but brought the chance of riotous frost fairs- which might quickly thaw to a mixed and floody spring where crop planting was a struggle, to be rapidly supplanted by a hot bucolic summer bringing anxious periods of drought, saved by rain that enabled a bountiful harvest, after which violent winds would blow in a stormy autumn as first one weather system gained ascendancy, only to be supplanted by another as the wind direction changed. During the following year all may be reversed, with complaints that an excessively wet mild winter didn’t destroy diseases, whilst the previous year’s baking hot summer was supplanted by a series of dull cool months threatening the all-important harvest, touching our ancestors with the ever present specter of famine.
Clusters of wet or dry years were as notable as clusters of cold or warm years, and sometimes all conditions coincided within one year demonstrating the variability which the Met office discounted.
The overwhelming impression I formed from reading the accounts of the vagaries of the climate of yesteryear was that they sounded exactly like today, with perhaps greater variability, extreme events and colder bits thrown in, although after the last few bitter winters the striking similarities with the past have become even closer. It is difficult to determine any evidence of notable climate change in recent years leading to a dramatic change in our climate or a surge in temperatures. What we can observe is a transition from the anomalously intermittently cold periods of the LIA together with lots of examples of climate variability.
Most notably the modern observer might feel that our current era seems to have lost the extreme winters of yesteryear- which in turn have had a considerable impact on the overall mean average temperature in the last few decades. However, once again history can show us that this apparent dearth of cold winters has had numerous precedents in our past.
Reginald Jeffery observed in his book ‘Was it Wet or was it fine,’ “By 1708 the middle aged would say where are our old winters?”
This query was being echoed on the other side of the Atlantic around the same time as the records of the Hudson Bay Company demonstrate that climate change was not restricted to Europe.
“Over the fifteen years between 1720 and 1735, the first snowfall of the year moved from the first week of September to the last…”
Thomas Jefferson -third President of the United States- kept extensive weather records and referring to the period around the 1770’s remarked;
““A change in our climate however is taking place very sensibly. Both heats and colds are become much more moderate within the memory even of the middle-aged. Snows are less frequent and less deep. They do not often lie, below the mountains, more than one, two, or three days, and very rarely a week. They are remembered to have been formerly frequent, deep, and of long continuance. The elderly inform me the earth used to be covered with snow about three months in every year. The rivers, which then seldom failed to freeze over in the course of the winter, scarcely ever do so now. (54)
A few decades later Noah Webster, 1758-1843 (founder- Webster’s dictionary) commented;
“The temperature of the winter season, in northern latitudes, has suffered a material change, and become warmer in modern, than it was in ancient times. … Indeed I know not whether any person, in this age, has ever questioned the fact.”
Towards the end of the 19th Century a correspondent in the Canadian Horticulturist monthly of 1880 (page 7) remarked;
“I do not know whether or not the climate of Ontario is really becoming permanently milder than formerly, but I do know that for the past 18 years or 20 years we have not experienced the same degree of cold as the seven years preceding.”
Writing in 1931 after several decades of compiling his book ‘Was it wet or was it Fine’ Reginald Jeffery remarked;
“I have been asked so often during the period that I have been doing this work this question, well after all this grubbing into the wealth of the past, do you think that our climate is changing or has changed? Where are the old snow storms? We never quite know where we are with regards to weather.”
Whilst around the same time a farmer from Buchan in Scotland wrote to his local newspaper;
“1934 has opened true to the modern tradition of open, snowless winters. The long ago winters are no precedent for our modern samples. During the last decade, during several Januarys the lark has heralded spring up in the lift from the middle to the end of the month. Not full fledged songs but preliminary bars in an effort to adapt to our climatic change.”
It then goes on to say;
“It is unwise to assume that the modern winters have displaced the old indefinitely” and also; “Our modern winters have induced an altered agricultural regime”
In order to be able to offer a more rounded picture of our ever changing and variable climate, it might be useful if scientists were less credulous of the infinite accuracy of unlikely proxies and took more notice of the great wealth of ‘anecdotal’ accounts. This might help to strike a better balance between observed records and scientific data often derived from uncertain and fragmented raw data of questionable provenance, that has then been subject to highly complex statistical analysis. The end result is the presentation of data that claims considerable-but unlikely- accuracy. To paraphrase Hubert Lamb we can know the ‘tendency’ but not the ‘precision’ when we delve back in time. Uncertainty shrouds much of the past and in consequence perhaps we believe we know much more than we currently do.
JC note: For the last several months, Tony has been sending me snippets from his research. I find the climate-history nexus to be fascinating. I offered to post this on Climate Etc. As with all guest posts, the views expressed here are those of Tony Brown, and my publishing this here does not imply any endorsement by myself.