CHARLES DICKENS AND THE ARTISTS AS CLIMATE REPORTERS
The 1790s and the first years of the new century produced a number of pleasant, warm summers in England and on the continent of Europe.
And apart from the severity of 1794–5 the winters were less cold than in the 1780s.
But 1809 brought the first of a long series of colder summers, and the decade of 1810–19 produced mostly cold seasons, for which the volcanic dust in the atmosphere has been blamed.
Indeed, the descriptions of ‘old-fashioned winters’ for which Charles Dickens became famous in his books may owe something to the fact — exceptional for London — that of the first nine Christmases of his life, between 1812 and 1820, six were white with either frost or snow.
That decade from 1810 to 1819 was the coldest in England since the 1690s.
The colder seasons returning in the early nineteenth century led to the designing of certain articles of warm underwear for women, notably the ‘bosom friend’, and brought to an end the daring fashions begun in the post-revolutionary 1790s in France, which ‘exposed the person’ a good deal.
It was remarked at the time that it was the north wind which enforced a return to modesty in women’s dress.
It appears from statistical studies of the changes of fashion in landscape painting that John Constable’s pictures, like those of others of his contemporaries and of the Netherlands School in the seventeenth century, tell us something about the characteristic summer weather of their times (figs. 88a and b).
Surveys of the cloud cover in European representational style paintings of various periods have shown averages of nearly 80 per cent cover in pictures from the period 1550–1700, 50–75 per cent at various times in the eighteenth century, 70–75 per cent in Constable’s and Turner’s time (1790–1840) and 55–70 per cent in the twentieth century.
These variations recorded by artists working out of doors, generally in the summer half of the year, are in line with what might be supposed from the known variations of summer temperature, though it appears that the swings of fashion registered by the artists probably exaggerated the variations of mean cloudiness.
In this they may well have been faithful to the subjective impressions of the people living at the respective times.
Another aspect of the nineteenth-century scene which we find portrayed, apparently authentically, in the work of painters down the ages is the increasing smoke pollution of London’s air and that of other European cities.
Brimblecombe has traced this in paintings from the fifteenth century to our own times.
The prevailing sky colour gradually changes from blue to yellowish and then to pinkish greys.
This and the other types of historical evidence indicate that the pollution of London’s air rose sharply with the introduction of the burning of coal from Newcastle and Tyneside in Tudor times and from 1690 to 1900 maintained a nearly constant high level.
TO BE CONTINUED ...
CLIMATE, HISTORY AND THE MODERN WORLD
Re: CLIMATE, HISTORY AND THE MODERN WORLD
TOWARDS THE MID-NINETEENTH CENTURY AND THE BEGINNINGS OF THE GREAT RECESSION OF THE GLACIERS
The 1820s and 1830s introduced a return to greater warmth in Britain and Europe and were distinguished, particularly in the 1820s, by genial warm springs and autumns.
And 1826 produced the warmest summer in the whole 300-year series of temperature observations in England, apparently slightly exceeding the record of 1976.
But there was still a great variability from year to year.
In August 1829 in Scotland the weather turned cold at the beginning with northerly and northeasterly winds, and the forty hours of rainfall on the 3rd and 4th produced unheard—of flooding of the rivers all over the northeast of the country which washed away a huge number of bridges and river-side buildings and altered the course of some estuaries.
Rain fell on twenty-eight days of that month in the usually dry lowlands of north-eastern Scotland.
The measured totals for the month, where available, seem to have been up to 2 1/2 times the long-term average.
The winters of 1821–2 and 1833–4, like that of 1845–6, were close to the mildest in the record.
But those of 1819–20, 1822–3, 1829–30 and 1837–8, as well as several in the 1840s, were very cold.
In 1829–30 the Bodensee (Lake Constance) in central Europe froze over completely for the first time since 1740 — it did not happen again until 1963, though it had happened five times in the seventeenth century and four times between 1563 and 1600.
And 1837–8 was such an extreme winter in Scandinavia that there was ice all the way from Skagen (the north tip of Denmark) to the southernmost point of Norway and round along the southwest coast of Norway as far out to sea as the eye could see.
(In March 1838 the ice on this Atlantic coast was drifting back towards the south again.)
Many of the springs and autumns in the 1820s, 1830s and 1840s in England were wet, and this combined with the experience of cooler and wetter summers after 1810 and in the 1840s (apart from 1846) seems to have led to general abandonment of the practice of irrigation on the farms which had begun in the drier periods of the eighteenth century, notably the 1740s.
There were other, notably prolonged, wet seasons in individual years later in the nineteenth century in England, particularly in 1848, 1852, 1872, 1877 and 1882.
The continuing variability of the seasons in England in the 1840s brought several more unpleasantly cold summers but also one more very hot summer, in 1846.
In that year the heat seems to have extended far across northern Europe and Asia to melt some of the permafrost in the tundras of northeast Siberia, where the commander of a small Russian survey ship in the River Lena described his difficulty of finding the river in the vast flooded landscape.
The river was identified only by ‘the rushing and roaring of the stream.'
'The river rolled against us trees, moss and large masses of peat.’
At one point ‘an elephants head’ reared at times out of the water, and being ultimately washed against the side of the ship, and there secured for a time, the ships company were able to examine the newly released mammoth before it sank once again into the mire.
The winters of the 1840s in England were also a ‘mixed bag’, including at least three that were very cold but one (the winter of 1845–6) that was so mild that it led Sabine, then Foreign Secretary of the Royal Society and soon to be one of the founders of the Meteorological Society, to observe that the Gulf Stream extended far beyond its usual bounds.
TO BE CONTINUED ...
The 1820s and 1830s introduced a return to greater warmth in Britain and Europe and were distinguished, particularly in the 1820s, by genial warm springs and autumns.
And 1826 produced the warmest summer in the whole 300-year series of temperature observations in England, apparently slightly exceeding the record of 1976.
But there was still a great variability from year to year.
In August 1829 in Scotland the weather turned cold at the beginning with northerly and northeasterly winds, and the forty hours of rainfall on the 3rd and 4th produced unheard—of flooding of the rivers all over the northeast of the country which washed away a huge number of bridges and river-side buildings and altered the course of some estuaries.
Rain fell on twenty-eight days of that month in the usually dry lowlands of north-eastern Scotland.
The measured totals for the month, where available, seem to have been up to 2 1/2 times the long-term average.
The winters of 1821–2 and 1833–4, like that of 1845–6, were close to the mildest in the record.
But those of 1819–20, 1822–3, 1829–30 and 1837–8, as well as several in the 1840s, were very cold.
In 1829–30 the Bodensee (Lake Constance) in central Europe froze over completely for the first time since 1740 — it did not happen again until 1963, though it had happened five times in the seventeenth century and four times between 1563 and 1600.
And 1837–8 was such an extreme winter in Scandinavia that there was ice all the way from Skagen (the north tip of Denmark) to the southernmost point of Norway and round along the southwest coast of Norway as far out to sea as the eye could see.
(In March 1838 the ice on this Atlantic coast was drifting back towards the south again.)
Many of the springs and autumns in the 1820s, 1830s and 1840s in England were wet, and this combined with the experience of cooler and wetter summers after 1810 and in the 1840s (apart from 1846) seems to have led to general abandonment of the practice of irrigation on the farms which had begun in the drier periods of the eighteenth century, notably the 1740s.
There were other, notably prolonged, wet seasons in individual years later in the nineteenth century in England, particularly in 1848, 1852, 1872, 1877 and 1882.
The continuing variability of the seasons in England in the 1840s brought several more unpleasantly cold summers but also one more very hot summer, in 1846.
In that year the heat seems to have extended far across northern Europe and Asia to melt some of the permafrost in the tundras of northeast Siberia, where the commander of a small Russian survey ship in the River Lena described his difficulty of finding the river in the vast flooded landscape.
The river was identified only by ‘the rushing and roaring of the stream.'
'The river rolled against us trees, moss and large masses of peat.’
At one point ‘an elephants head’ reared at times out of the water, and being ultimately washed against the side of the ship, and there secured for a time, the ships company were able to examine the newly released mammoth before it sank once again into the mire.
The winters of the 1840s in England were also a ‘mixed bag’, including at least three that were very cold but one (the winter of 1845–6) that was so mild that it led Sabine, then Foreign Secretary of the Royal Society and soon to be one of the founders of the Meteorological Society, to observe that the Gulf Stream extended far beyond its usual bounds.
TO BE CONTINUED ...
Re: CLIMATE, HISTORY AND THE MODERN WORLD
THE IRISH POTATO FAMINE
The human history of the 1840s has generally been written in terms of the ideas and rising pressure of movements towards democracy and universal suffrage that were occupying the nations of Europe, until they broke out in the year of revolutions in 1848.
It might be worth investigation nevertheless to discover what part, if any, the weather and its effects upon agriculture and the urban poor played in all this.
In one corner of Europe, at least, it had a critical effect, the turning point in Ireland’s history brought by the great potato famine.
The summer of 1846, which was warm in Europe generally, was humid, with moist southerly winds, and cyclonic at the Atlantic fringe and also at times in much of northern Europe.
This provided ideal conditions for the potato blight fungus (Phytophthora infestans), which had made its first appearance in Europe (in a shipload from America which included diseased tubers) in 1845 and spread quickly.
The organism multiplies rapidly in periods of some days in succession with temperatures continuously above 10°C and relative humidity never below 90 per cent saturation, permitting the exposed plant surfaces to remain wet.
We read in a farm diary from as far away as Jaeren in southwest Norway that in 1846 the alternations of rain and sun, always with warmth, ripened the corn quickly and it was safely got in by 29 August, but ‘the potatoes rotted again’.
In Ireland, where the potato was the staple crop on the multitudes of small farms, 80 per cent of them under 6 hectares (15 acres) and many only a fifth of that size, the effect was devastating.
Despite relief measures, particularly large imports of maize from the United States, enormous numbers of the people died.
Over six years of continuing outbreaks, aggravated by an epidemic of typhus which also was not confined to Ireland, it is estimated that there were a million deaths in Ireland, and the flow of emigration began.
The population in 1851 had already dropped by nearly a quarter from its peak of 8 1/2 million in 1845, and by the twentieth century it had fallen by a half and has never since approached the 1845 level.
TO BE CONTINUED ...
The human history of the 1840s has generally been written in terms of the ideas and rising pressure of movements towards democracy and universal suffrage that were occupying the nations of Europe, until they broke out in the year of revolutions in 1848.
It might be worth investigation nevertheless to discover what part, if any, the weather and its effects upon agriculture and the urban poor played in all this.
In one corner of Europe, at least, it had a critical effect, the turning point in Ireland’s history brought by the great potato famine.
The summer of 1846, which was warm in Europe generally, was humid, with moist southerly winds, and cyclonic at the Atlantic fringe and also at times in much of northern Europe.
This provided ideal conditions for the potato blight fungus (Phytophthora infestans), which had made its first appearance in Europe (in a shipload from America which included diseased tubers) in 1845 and spread quickly.
The organism multiplies rapidly in periods of some days in succession with temperatures continuously above 10°C and relative humidity never below 90 per cent saturation, permitting the exposed plant surfaces to remain wet.
We read in a farm diary from as far away as Jaeren in southwest Norway that in 1846 the alternations of rain and sun, always with warmth, ripened the corn quickly and it was safely got in by 29 August, but ‘the potatoes rotted again’.
In Ireland, where the potato was the staple crop on the multitudes of small farms, 80 per cent of them under 6 hectares (15 acres) and many only a fifth of that size, the effect was devastating.
Despite relief measures, particularly large imports of maize from the United States, enormous numbers of the people died.
Over six years of continuing outbreaks, aggravated by an epidemic of typhus which also was not confined to Ireland, it is estimated that there were a million deaths in Ireland, and the flow of emigration began.
The population in 1851 had already dropped by nearly a quarter from its peak of 8 1/2 million in 1845, and by the twentieth century it had fallen by a half and has never since approached the 1845 level.
TO BE CONTINUED ...
Re: CLIMATE, HISTORY AND THE MODERN WORLD
MID-NINETEENTH CENTURY IN THE UNITED STATES
The climate of the period from the 1830s to the 1860s in the United States has been investigated by Eberhard Wahl and associates at the University of Wisconsin in Madison, using a network of official weather station records which included the earliest of their kind from the middle of the continent.
The results showed a climate that was colder than the 1931–60 averages over the eastern and central parts of the country by between 1 and 2°C in the interior in each season of the year and by over 2.0°C (3.6°F) in the early autumn.
In the 1850s and 1860s, for which data extend to the Pacific coast, it is seen that the mountain states were on the other hand up to 1°C warmer than in 1931–60, up to 1.5°C in spring, summer and early autumn.
Precipitation was around 20 per cent greater than in recent times over the same area, but in winter the north-south belt of up to 40 per cent greater down-put of rain and snow lay over the Middle West.
This distribution makes it clear that, as we also deduced for the sixteenth-and seventeenth-century climax of the Little Ice Age, the wind circulation was more meridional (with fewer west winds) than in the twentieth century.
In particular, there must have been more northerly winds over the eastern and central parts of North America and more southerly winds over the west.
But some changes of longitude of the main features of the pattern must have taken place; for the waggoners trekking out west to California in 1849 found the Middle West a virtual desert.
TO BE CONTINUED ...
The climate of the period from the 1830s to the 1860s in the United States has been investigated by Eberhard Wahl and associates at the University of Wisconsin in Madison, using a network of official weather station records which included the earliest of their kind from the middle of the continent.
The results showed a climate that was colder than the 1931–60 averages over the eastern and central parts of the country by between 1 and 2°C in the interior in each season of the year and by over 2.0°C (3.6°F) in the early autumn.
In the 1850s and 1860s, for which data extend to the Pacific coast, it is seen that the mountain states were on the other hand up to 1°C warmer than in 1931–60, up to 1.5°C in spring, summer and early autumn.
Precipitation was around 20 per cent greater than in recent times over the same area, but in winter the north-south belt of up to 40 per cent greater down-put of rain and snow lay over the Middle West.
This distribution makes it clear that, as we also deduced for the sixteenth-and seventeenth-century climax of the Little Ice Age, the wind circulation was more meridional (with fewer west winds) than in the twentieth century.
In particular, there must have been more northerly winds over the eastern and central parts of North America and more southerly winds over the west.
But some changes of longitude of the main features of the pattern must have taken place; for the waggoners trekking out west to California in 1849 found the Middle West a virtual desert.
TO BE CONTINUED ...
Re: CLIMATE, HISTORY AND THE MODERN WORLD
EUROPE AND THE ARCTIC FRINGE
In 1840 a shift in the ocean current pattern seems to have taken place, which gave Iceland fifteen years of near immunity from the ice of the Arctic seas and for a few years (1845–51) made a large cod fishery possible off west Greenland.
At the same time, Europe experienced on balance a somewhat colder climate.
The wind circulation features involved seem to have been frequent ‘blocking’ anticyclones over northern Europe, with easterly winds over much of the continent but giving southerly winds in the Iceland region: these warm winds occasionally extended east to Europe, however.
In 1855 a further shift seems to have renewed the strength of the ice-bearing current off east Greenland and brought the ice back to Iceland.
And soon the westerly and southwesterly winds over the North Atlantic Ocean were regenerated, bringing warmer seasons to Europe and starting a recession of the glaciers.
This lasted through the 1860s.
The summer of 1868, in particular, produced a remarkable number of hot days with temperatures over 30°C in England, including the record value of 38.1°C (100.6 °F) at Tonbridge, Kent on 22 July.
The winter of 1868–9 in England was the warmest of the entire record with a mean temperature of 6.8°C, which is more normal for the west coast of Ireland and warmer than some springs of the past in England.
Also in the 1870s Europe enjoyed mostly warm seasons and mild winters, apart from some severe weather in the Februarys of 1870 and 1875 and a longer frost in December 1870 and January 1871.
The year 1872 was very wet in England and Wales, and from 1875 onwards most of the summers were wet.
TO BE CONTINUED ...
In 1840 a shift in the ocean current pattern seems to have taken place, which gave Iceland fifteen years of near immunity from the ice of the Arctic seas and for a few years (1845–51) made a large cod fishery possible off west Greenland.
At the same time, Europe experienced on balance a somewhat colder climate.
The wind circulation features involved seem to have been frequent ‘blocking’ anticyclones over northern Europe, with easterly winds over much of the continent but giving southerly winds in the Iceland region: these warm winds occasionally extended east to Europe, however.
In 1855 a further shift seems to have renewed the strength of the ice-bearing current off east Greenland and brought the ice back to Iceland.
And soon the westerly and southwesterly winds over the North Atlantic Ocean were regenerated, bringing warmer seasons to Europe and starting a recession of the glaciers.
This lasted through the 1860s.
The summer of 1868, in particular, produced a remarkable number of hot days with temperatures over 30°C in England, including the record value of 38.1°C (100.6 °F) at Tonbridge, Kent on 22 July.
The winter of 1868–9 in England was the warmest of the entire record with a mean temperature of 6.8°C, which is more normal for the west coast of Ireland and warmer than some springs of the past in England.
Also in the 1870s Europe enjoyed mostly warm seasons and mild winters, apart from some severe weather in the Februarys of 1870 and 1875 and a longer frost in December 1870 and January 1871.
The year 1872 was very wet in England and Wales, and from 1875 onwards most of the summers were wet.
TO BE CONTINUED ...
Re: CLIMATE, HISTORY AND THE MODERN WORLD
TOWARDS THE END OF THE CENTURY
A more serious reversion to colder climate came with the year 1879, a year well within the class of the 1690s.
Through December 1878 and January 1879 the temperature in England stayed mainly below the freezing point, and it was very snowy; the spring was cold, with May colder than many an April; the summer was the wettest and one of the seven coldest in the long instrument records for England; it was followed by a notably cold autumn and another near freezing month in December.
The cold wet weather delayed the ripening of the harvest, so that even in East Anglia in some places the corn had not been gathered in by Christmas.
There were to be a number more skating winters in England and Holland, and amusements on the ice on the Swedish Baltic coast (fig. 89), before the stronger warming in the twentieth century came in.
The decline of English agriculture, which lasted for fifty years, dated from this time.
The harvests had been affected by difficult seasons from 1875, and the competition on Britain’s free trade market of cheap North American wheat from the prairies was beginning to be felt.
1879 turned the decline into a collapse.
Within a few years the cornlands of the northwestern half of England had been converted to grass, and soon that brought no profit as frozen meat began to come from Australia, New Zealand and South America.
The farmworkers began to leave the land for the towns and to emigrate overseas in great numbers.
Other European countries protected their peasantry against the American competition by import dues.
But the effects of 1879 and the difficult years with cold winters and wet summers which followed were not confined to England.
The peak emigration of people from the countries of northern, central and western Europe was in the 1880s.
The years 1876–9 also brought droughts, monsoon failures and famine in China and India.
The old stories of medieval Europe’s famine situations of outbreaks of cannibalism and children sold into slavery repeated themselves in these years in the Far East.
The temperature records in China (fig. 86) and indicators such as the freezing dates of Lake Suwa in central Japan (fig. 90) show that this was one of the severest phases of the Little Ice Age in the Far East.
The deaths due to famine in the late 1870s in India and China have been estimated at 14–18 million.
The historical documentary information which begins to be available from the southern hemisphere in the centuries described in this and the previous chapter seems to confirm that there too a colder climate developed during the last millennium.
Glaciers advanced in South America and New Zealand, and there were appropriate changes in the New Zealand forests.
But the timing of the severest phases was different, it seems almost opposite, to that in the northern hemisphere.
We have referred to evidence of this in chapter 3 (p. 39).
Captain Cook's voyages in the 1770s and others on to the 1830s confirm that the Antarctic sea ice was more restricted and open sea extended farther south, although those were times when the northern polar ice was well forward and troubling Iceland.
Later in the nineteenth century, in the 1850s and around 1900, the southern sea ice extended farther north and there were many accounts from the sailing ships of those days of sightings of the great tabular icebergs calved from the Antarctic inland ice drifting to much lower latitudes, off the River Plate and approaching the other southern continents.
After 1894–5, when there was a good deal of ice on the Thames in London, there was a long respite from severe winters in England and in Europe generally.
Not again was there a month with mean temperature below the freezing point in England until January 1940.
Only the winters of 1916–17 and 1928–9 during that interval of forty-five years could be considered in any way severe, the February in both cases coming near to being a freezing month in England and causing some ice to appear on the Thames.
The much more severe winter of 1962–3 (3-month mean temperature in central England −0.3°C, January −2.1° C) never brought the water temperature in London’s river below about 10°C (50°F), owing to all the industrial and urban effluents now passed into the river.
(That winter was colder than some in which frost fairs were held on the river in London in the past. The progress of urbanization suggests rather that the pastimes in future cold winters will be to skate on the Thames at Hampton Court —at the western limit of the metropolis—and then swim in it from Westminster pier!)
It should plainly be desirable to update our portrayal in fig. 91a of the course of world-average temperature at the surface of the Earth, as indeed has been attempted in various quarters.
The most authoritative version is due to the (WMO/UNEP) Intergovernmental Panel on Climate Change14 (IPCC for short).
The curve here shown as fig. 91b represents the IPCC figures when looked at as the successive five-year means from 1860 to 1989.
The three-year mean for the remarkably warm years 1990–2 is the last point at the right-hand end of the graph.
The overall shape of this historical curve is the product of successive revisions adjusting the values for urban and industrial warming and any other possibly distorting influences at the observation sites — not least the changes that have taken place in the observing practices at sea with ever bigger ships, changes in the height of their decks above the water, and measurements in recent decades being made within the vessel in intake pipes instead of in open buckets.
This writer is inclined to the belief that, however careful the observing procedures and however carefully studied the adjustments applied afterwards to the observations, to declare a value for the world average or an area average to within some hundredths of a degree centigrade is an unattainable ideal.
All responsible researchers agree that the temperatures measured must be adjusted for peculiarities of the site and the changes of these peculiarities with time.
All these things have led to revisions of the data.
Urban and industrial influences also change with time, as does the pollution of various kinds which may influence the data.
Also, it is now appreciated that the climates of islands, big and small, differ from those over the open sea as well as from the climate of the nearest extensive land-masses.
Even the inhabited camps in polar wastes create their own climates through the artificially generated heat, smoke and pollution, all of which tend to be trapped locally and held beneath the temperature inversions.
The light wind speeds below the inversion also lead to a strong local concentration of the effects.
Hence, adjustments must be attempted even though they introduce an arbitrary element into the results.
Our fig. 91 was derived from the average surface temperatures for ten-degree latitude zones around the whole Earth between latitudes 80°N and 60 °S, presented in 1963 by the late J.Murray Mitchell Jr to the WMO/UNESCO Rome symposium on changes of climate, for successive five-year periods from 1870 (in the northern hemisphere from 1840) to 1959 and later extended to the 1970s.
The revised version put before us in fig. 91b, using for the first time the now available results of the fine collection and survey of the world's ocean surface temperatures since the 1850s by C.K. Folland and his associates in the British Meteorological Office and the work on land stations all over the world by P.D. Jones and others in the Climatic Research Unit, Norwich, gives a disconcertingly different picture of the course of world temperature history that should not pass without notice.
The differences between the course of world temperature in the twentieth century as displayed in figs. 91a and 91b must be partly explained by the fact that the survey represented in fig. 91 omitted the Antarctic and all latitudes south of 60°S, where all our evidence makes clear that very substantially higher temperatures have been observed since about 1950, as is also true for New Zealand.
The other main contribution to the discrepancy is the significant warming of the tropics, though by only some tenths of a degree but applying to the great area of the tropical zone.
There are, nevertheless, points of agreement between the two versions.
It is agreed that the 1880s and early 1890s were a cold time, though not everywhere in the northern hemisphere oceans, and that the twentieth century has been generally warmer.
Warming was rapid from about 1920 to 1940.
The cooling which set in in the 1940s had a wobbly course, but the climatic record continued generally colder in the northern hemisphere until some time after 1970.
In the southern hemisphere, particularly the Antarctic and the sub-Antarctic ocean zone, there was a rapid warming going on from about 1950 onwards.
Despite the rapid rise of world temperature after 1975 indicated by our fig. 91b, there has been a noteworthy occurrence — seen, for example, in the Danish temperature record here reproduced in fig. 28a (p. 80) and in other records in North America and Europe of further cold events or some continued colder conditions until 1985 to 1987.
The state of affairs at the time of writing (1994) seems to be that, after truly exceptional warmth in the years 1989–91, there has been some fall of temperature world-wide, which has been attributed by many to the effects of the great volcanic eruption of Mount Pinatubo in the Philippines in June 1991.
TO BE CONTINUED ...
A more serious reversion to colder climate came with the year 1879, a year well within the class of the 1690s.
Through December 1878 and January 1879 the temperature in England stayed mainly below the freezing point, and it was very snowy; the spring was cold, with May colder than many an April; the summer was the wettest and one of the seven coldest in the long instrument records for England; it was followed by a notably cold autumn and another near freezing month in December.
The cold wet weather delayed the ripening of the harvest, so that even in East Anglia in some places the corn had not been gathered in by Christmas.
There were to be a number more skating winters in England and Holland, and amusements on the ice on the Swedish Baltic coast (fig. 89), before the stronger warming in the twentieth century came in.
The decline of English agriculture, which lasted for fifty years, dated from this time.
The harvests had been affected by difficult seasons from 1875, and the competition on Britain’s free trade market of cheap North American wheat from the prairies was beginning to be felt.
1879 turned the decline into a collapse.
Within a few years the cornlands of the northwestern half of England had been converted to grass, and soon that brought no profit as frozen meat began to come from Australia, New Zealand and South America.
The farmworkers began to leave the land for the towns and to emigrate overseas in great numbers.
Other European countries protected their peasantry against the American competition by import dues.
But the effects of 1879 and the difficult years with cold winters and wet summers which followed were not confined to England.
The peak emigration of people from the countries of northern, central and western Europe was in the 1880s.
The years 1876–9 also brought droughts, monsoon failures and famine in China and India.
The old stories of medieval Europe’s famine situations of outbreaks of cannibalism and children sold into slavery repeated themselves in these years in the Far East.
The temperature records in China (fig. 86) and indicators such as the freezing dates of Lake Suwa in central Japan (fig. 90) show that this was one of the severest phases of the Little Ice Age in the Far East.
The deaths due to famine in the late 1870s in India and China have been estimated at 14–18 million.
The historical documentary information which begins to be available from the southern hemisphere in the centuries described in this and the previous chapter seems to confirm that there too a colder climate developed during the last millennium.
Glaciers advanced in South America and New Zealand, and there were appropriate changes in the New Zealand forests.
But the timing of the severest phases was different, it seems almost opposite, to that in the northern hemisphere.
We have referred to evidence of this in chapter 3 (p. 39).
Captain Cook's voyages in the 1770s and others on to the 1830s confirm that the Antarctic sea ice was more restricted and open sea extended farther south, although those were times when the northern polar ice was well forward and troubling Iceland.
Later in the nineteenth century, in the 1850s and around 1900, the southern sea ice extended farther north and there were many accounts from the sailing ships of those days of sightings of the great tabular icebergs calved from the Antarctic inland ice drifting to much lower latitudes, off the River Plate and approaching the other southern continents.
After 1894–5, when there was a good deal of ice on the Thames in London, there was a long respite from severe winters in England and in Europe generally.
Not again was there a month with mean temperature below the freezing point in England until January 1940.
Only the winters of 1916–17 and 1928–9 during that interval of forty-five years could be considered in any way severe, the February in both cases coming near to being a freezing month in England and causing some ice to appear on the Thames.
The much more severe winter of 1962–3 (3-month mean temperature in central England −0.3°C, January −2.1° C) never brought the water temperature in London’s river below about 10°C (50°F), owing to all the industrial and urban effluents now passed into the river.
(That winter was colder than some in which frost fairs were held on the river in London in the past. The progress of urbanization suggests rather that the pastimes in future cold winters will be to skate on the Thames at Hampton Court —at the western limit of the metropolis—and then swim in it from Westminster pier!)
It should plainly be desirable to update our portrayal in fig. 91a of the course of world-average temperature at the surface of the Earth, as indeed has been attempted in various quarters.
The most authoritative version is due to the (WMO/UNEP) Intergovernmental Panel on Climate Change14 (IPCC for short).
The curve here shown as fig. 91b represents the IPCC figures when looked at as the successive five-year means from 1860 to 1989.
The three-year mean for the remarkably warm years 1990–2 is the last point at the right-hand end of the graph.
The overall shape of this historical curve is the product of successive revisions adjusting the values for urban and industrial warming and any other possibly distorting influences at the observation sites — not least the changes that have taken place in the observing practices at sea with ever bigger ships, changes in the height of their decks above the water, and measurements in recent decades being made within the vessel in intake pipes instead of in open buckets.
This writer is inclined to the belief that, however careful the observing procedures and however carefully studied the adjustments applied afterwards to the observations, to declare a value for the world average or an area average to within some hundredths of a degree centigrade is an unattainable ideal.
All responsible researchers agree that the temperatures measured must be adjusted for peculiarities of the site and the changes of these peculiarities with time.
All these things have led to revisions of the data.
Urban and industrial influences also change with time, as does the pollution of various kinds which may influence the data.
Also, it is now appreciated that the climates of islands, big and small, differ from those over the open sea as well as from the climate of the nearest extensive land-masses.
Even the inhabited camps in polar wastes create their own climates through the artificially generated heat, smoke and pollution, all of which tend to be trapped locally and held beneath the temperature inversions.
The light wind speeds below the inversion also lead to a strong local concentration of the effects.
Hence, adjustments must be attempted even though they introduce an arbitrary element into the results.
Our fig. 91 was derived from the average surface temperatures for ten-degree latitude zones around the whole Earth between latitudes 80°N and 60 °S, presented in 1963 by the late J.Murray Mitchell Jr to the WMO/UNESCO Rome symposium on changes of climate, for successive five-year periods from 1870 (in the northern hemisphere from 1840) to 1959 and later extended to the 1970s.
The revised version put before us in fig. 91b, using for the first time the now available results of the fine collection and survey of the world's ocean surface temperatures since the 1850s by C.K. Folland and his associates in the British Meteorological Office and the work on land stations all over the world by P.D. Jones and others in the Climatic Research Unit, Norwich, gives a disconcertingly different picture of the course of world temperature history that should not pass without notice.
The differences between the course of world temperature in the twentieth century as displayed in figs. 91a and 91b must be partly explained by the fact that the survey represented in fig. 91 omitted the Antarctic and all latitudes south of 60°S, where all our evidence makes clear that very substantially higher temperatures have been observed since about 1950, as is also true for New Zealand.
The other main contribution to the discrepancy is the significant warming of the tropics, though by only some tenths of a degree but applying to the great area of the tropical zone.
There are, nevertheless, points of agreement between the two versions.
It is agreed that the 1880s and early 1890s were a cold time, though not everywhere in the northern hemisphere oceans, and that the twentieth century has been generally warmer.
Warming was rapid from about 1920 to 1940.
The cooling which set in in the 1940s had a wobbly course, but the climatic record continued generally colder in the northern hemisphere until some time after 1970.
In the southern hemisphere, particularly the Antarctic and the sub-Antarctic ocean zone, there was a rapid warming going on from about 1950 onwards.
Despite the rapid rise of world temperature after 1975 indicated by our fig. 91b, there has been a noteworthy occurrence — seen, for example, in the Danish temperature record here reproduced in fig. 28a (p. 80) and in other records in North America and Europe of further cold events or some continued colder conditions until 1985 to 1987.
The state of affairs at the time of writing (1994) seems to be that, after truly exceptional warmth in the years 1989–91, there has been some fall of temperature world-wide, which has been attributed by many to the effects of the great volcanic eruption of Mount Pinatubo in the Philippines in June 1991.
TO BE CONTINUED ...
Re: CLIMATE, HISTORY AND THE MODERN WORLD
THE TWENTIETH-CENTURY WARMTH
It was during the second and third decades of the new century that the climatic warming became noticeable to everybody.
The phenomenon is well seen on figs. 28, 30, 36 and 86.
In England, and probably in many other places, the temperature jump from one decade to the next was not as great as the change from the 1690s to the first decade of the eighteenth century, but it was to be much longer sustained.
The apparent changes of world temperature over about the last hundred years are shown in fig. 91.
Of the various curves shown, that for the northern hemisphere is doubtless the most reliable.
(The difficulties of estimation over parts of the world where regular observation sites are few and unevenly scattered, because of extensive oceans or ice, restrict the accuracy and have therefore restricted the areas of the Earth which these curves are designed to cover.)
The change of long-term prevailing temperature in England over this period is evidently similar to that averaged over the Earth as a whole.
Places near the Arctic fringe — such as Iceland, Spitsbergen and even Toronto — experienced warming that was from twice to five times as great.
This was accompanied by, and its magnitude in part explained by, withdrawal northwards of the boundary of persistent ice and snow.
In Spitsbergen the open season for shipping at the coal port lengthened from three months in the years before 1920 to over seven months of the year by the late 1930s.
The average total area of the Arctic sea ice seems to have declined by between 10 and 20 per cent over that time.
Even the equatorial oceans and small islands near the equator warmed up by about the same amount as the computed world average.
In a few areas in low latitudes, however, where there were changes in the location or extent of upwelling colder water from the deeper ocean, because of the upwelling there was some cooling.
When account is also taken of the changes in the atmospheric circulation, and hence in the distribution of rainfall and its variability as well, it is hardly too much to say that the twentieth-century climatic regime from 1920 to 1960 changed the world.
The prevailing westerly winds of middle latitudes increased their dominance (fig. 17, p. 53, illustrates this in the case of the British Isles), as the cyclones of the subpolar zone became bigger and spread their wind circulation farther into the Arctic.
In consequence of the more frequent westerly winds, all those places which derive their rainfall from moisture transported from the west experienced increased and more reliable rainfall.
This is illustrated in fig. 92 for places near 50°N across the plains of Europe into central Asia.
The same happened at places with western exposures in corresponding latitudes in the southern hemisphere.
And more moisture penetrated into high latitudes to be deposited as snow on the ice-sheets in north Greenland and Antarctica.
In middle latitudes in the Americas the situation was different, because in the rain-shadow of the Rockies and the Andes increased westerly winds brought dryness, culminating in the disastrous droughts of the Dust-Bowl years in the 1930s in the United States Middle West.
In fig. 92 it may also be noticed that at Lisbon, as in other places in subtropical latitudes, rainfall also decreased.
This was due to the increased size, and some northward displacement, of the anticyclone belt.
Correspondingly, south of the Sahara the monsoons of west Africa penetrated farther north at that time.
And similarly the monsoon in India was at its most reliable, with only two partial failures in thirty-six years between 1925 and 1960.
In temperate latitudes the growing season increased in length — in England, and perhaps typically, the average length increased by about two weeks.
The frequency of snow and frost decreased generally.
The dates of last frost in spring became earlier and of first frost in autumn later, commonly by two weeks or more.
And the retreat of the glaciers after about 1925 became rapid.
It was almost entirely during the twentieth century warming that the Alpine glaciers disappeared from the valley floors up into the mountains.
Similarly great retreats occurred in Scandinavia, Iceland, Greenland, in the Americas and on the high mountains near the equator.
The upper limit of trees on the mountains of Europe and the northern forest limit in Lapland were affected by the warming.
Fig. 93 illustrates the overall change of scene from the early nineteenth-century landscape in the Alps.
Similar changes are recorded in pictures from many other valleys and in other parts of the world.
The ranges of birds and the northern and southern limits of various fish species in the oceans moved poleward during the twentieth-century warming, but this movement has been gradually reversed since about 1960.
Fig. 94 contrasts the open hilltop sites preferred for the luxury housing of the 1930s in England, following the trend of fashion set in Bath in the 1730s, with the sheltered valley-bottom sites which were favoured in the sixteenth century.
TO BE CONTINUED ...
It was during the second and third decades of the new century that the climatic warming became noticeable to everybody.
The phenomenon is well seen on figs. 28, 30, 36 and 86.
In England, and probably in many other places, the temperature jump from one decade to the next was not as great as the change from the 1690s to the first decade of the eighteenth century, but it was to be much longer sustained.
The apparent changes of world temperature over about the last hundred years are shown in fig. 91.
Of the various curves shown, that for the northern hemisphere is doubtless the most reliable.
(The difficulties of estimation over parts of the world where regular observation sites are few and unevenly scattered, because of extensive oceans or ice, restrict the accuracy and have therefore restricted the areas of the Earth which these curves are designed to cover.)
The change of long-term prevailing temperature in England over this period is evidently similar to that averaged over the Earth as a whole.
Places near the Arctic fringe — such as Iceland, Spitsbergen and even Toronto — experienced warming that was from twice to five times as great.
This was accompanied by, and its magnitude in part explained by, withdrawal northwards of the boundary of persistent ice and snow.
In Spitsbergen the open season for shipping at the coal port lengthened from three months in the years before 1920 to over seven months of the year by the late 1930s.
The average total area of the Arctic sea ice seems to have declined by between 10 and 20 per cent over that time.
Even the equatorial oceans and small islands near the equator warmed up by about the same amount as the computed world average.
In a few areas in low latitudes, however, where there were changes in the location or extent of upwelling colder water from the deeper ocean, because of the upwelling there was some cooling.
When account is also taken of the changes in the atmospheric circulation, and hence in the distribution of rainfall and its variability as well, it is hardly too much to say that the twentieth-century climatic regime from 1920 to 1960 changed the world.
The prevailing westerly winds of middle latitudes increased their dominance (fig. 17, p. 53, illustrates this in the case of the British Isles), as the cyclones of the subpolar zone became bigger and spread their wind circulation farther into the Arctic.
In consequence of the more frequent westerly winds, all those places which derive their rainfall from moisture transported from the west experienced increased and more reliable rainfall.
This is illustrated in fig. 92 for places near 50°N across the plains of Europe into central Asia.
The same happened at places with western exposures in corresponding latitudes in the southern hemisphere.
And more moisture penetrated into high latitudes to be deposited as snow on the ice-sheets in north Greenland and Antarctica.
In middle latitudes in the Americas the situation was different, because in the rain-shadow of the Rockies and the Andes increased westerly winds brought dryness, culminating in the disastrous droughts of the Dust-Bowl years in the 1930s in the United States Middle West.
In fig. 92 it may also be noticed that at Lisbon, as in other places in subtropical latitudes, rainfall also decreased.
This was due to the increased size, and some northward displacement, of the anticyclone belt.
Correspondingly, south of the Sahara the monsoons of west Africa penetrated farther north at that time.
And similarly the monsoon in India was at its most reliable, with only two partial failures in thirty-six years between 1925 and 1960.
In temperate latitudes the growing season increased in length — in England, and perhaps typically, the average length increased by about two weeks.
The frequency of snow and frost decreased generally.
The dates of last frost in spring became earlier and of first frost in autumn later, commonly by two weeks or more.
And the retreat of the glaciers after about 1925 became rapid.
It was almost entirely during the twentieth century warming that the Alpine glaciers disappeared from the valley floors up into the mountains.
Similarly great retreats occurred in Scandinavia, Iceland, Greenland, in the Americas and on the high mountains near the equator.
The upper limit of trees on the mountains of Europe and the northern forest limit in Lapland were affected by the warming.
Fig. 93 illustrates the overall change of scene from the early nineteenth-century landscape in the Alps.
Similar changes are recorded in pictures from many other valleys and in other parts of the world.
The ranges of birds and the northern and southern limits of various fish species in the oceans moved poleward during the twentieth-century warming, but this movement has been gradually reversed since about 1960.
Fig. 94 contrasts the open hilltop sites preferred for the luxury housing of the 1930s in England, following the trend of fashion set in Bath in the 1730s, with the sheltered valley-bottom sites which were favoured in the sixteenth century.
TO BE CONTINUED ...
Re: CLIMATE, HISTORY AND THE MODERN WORLD
Part III
CLIMATE IN THE MODERN WORLD AND QUESTIONS OVER THE FUTURE
CLIMATE SINCE 1950
ANOTHER TURNING POINT
Over the years since the 1940s it has become apparent that many of the tendencies in world climate which marked the previous fifty to eighty years or more have either ceased or changed.
It is undoubtedly this that has stimulated interest in climate and increased effort in climatic research in recent years.
It was only after the end of the Second World War that the benign trend of the climate towards general warming over those previous decades really came in for much scientific discussion and began to attract public notice.
Attention at that time was focused on where continuation of the trend might lead: on the possible disappearance of the Arctic sea ice by the end of the century, and what effect that might have on agriculture, and the possibilities which might open up farther north to grow food and settle a growing population.
Of course, apart from the question of trend, there have been since 1950, as before, the usual swings of climate from one year to the next and from one group of a few years to those immediately following.
These make it difficult to discern the direction of any trend until it has already been established for some time, perhaps even for some decades.
And, indeed, there have been many suggestions that the range of these short-term variations has widened since the middle of the century.
TO BE CONTINUED ...
CLIMATE IN THE MODERN WORLD AND QUESTIONS OVER THE FUTURE
CLIMATE SINCE 1950
ANOTHER TURNING POINT
Over the years since the 1940s it has become apparent that many of the tendencies in world climate which marked the previous fifty to eighty years or more have either ceased or changed.
It is undoubtedly this that has stimulated interest in climate and increased effort in climatic research in recent years.
It was only after the end of the Second World War that the benign trend of the climate towards general warming over those previous decades really came in for much scientific discussion and began to attract public notice.
Attention at that time was focused on where continuation of the trend might lead: on the possible disappearance of the Arctic sea ice by the end of the century, and what effect that might have on agriculture, and the possibilities which might open up farther north to grow food and settle a growing population.
Of course, apart from the question of trend, there have been since 1950, as before, the usual swings of climate from one year to the next and from one group of a few years to those immediately following.
These make it difficult to discern the direction of any trend until it has already been established for some time, perhaps even for some decades.
And, indeed, there have been many suggestions that the range of these short-term variations has widened since the middle of the century.
TO BE CONTINUED ...
Re: CLIMATE, HISTORY AND THE MODERN WORLD
VARIABILITY INCREASES
Such world-wide surveys as have been attempted seem to confirm the increase of variability of temperature and rainfall, as illustrated in figs. 95a and b.
Much the same applies to the atmospheric pressure distribution except that variability was low in the 1950s.
In Europe, as has been noted elsewhere by Professor Flohn and by Dr C.J.E. Schuurmans of the Netherlands meteorological service, there is a curious change in the pattern of variability: from some time between 1940 and 1960 onwards the occurrence of extreme seasons — both as regards temperature and rainfall — has notably increased, while the overall variability as determined largely by the remaining years has been rather lower than in the preceding decades.
Summer is an exception to this and even in Europe shows the more general experience of increased variability.
A world-wide list of the extreme seasons reported since 1960 makes impressive reading.
Among the items included are:
1960–9 Driest decade in central Chile since the 1770s and 1790s.
1962–3 Coldest winter in England since 1740.
1962–5 Driest four-year period in the eastern United States since records began in 1738.
1963–4 Driest winter in England and Wales since 1743; coldest winter over an area from the lower Volga basin and Caspian Sea to the Persian Gulf since 1745.
1965–6 Baltic Sea completely ice-covered.
1968 Arctic sea ice half surrounded Iceland for the first time since 1888.
1968–73 Severest phase thus far of the prolonged drought in the Sahel zone of Africa, surpassing all recorded (twentieth-century) experience.
1971–2 Coldest winter in more than two hundred years of record in parts of eastern European Russia and Turkey: River Tigris frozen over.
1972 Greatest heat wave (in July) in the long records for north Finland and northern Russia.
1973–4 Floods beyond all previous recorded experience stretching across the central Australian desert.
1974–5 Mildest winter in England since 1834. Virtually no ice on the Baltic.
1975–6 Great European drought produced the most severe soil moisture deficit that can be established in the London (Kew) records since 1698.
1975 and Greatest heat waves in the records for Denmark and the 1976 Netherlands and, in some particulars, for England also.
1976–7 Severest winter in the temperature records (which begin in 1738) for the eastern United States.
1978–9 Severest winter and lowest temperatures recorded in two hundred years in parts of northern Europe and perhaps also in the Moscow region. Snowfalls also extreme in some parts of northern Europe.
This shortened list omits most of the notable events reported in these years in the southern hemisphere and other parts of the world where instrument records do not extend so far back.
Cases affecting the intermediate seasons, the springs and autumns, have also been omitted.
These variations, perhaps more than any underlying trend towards a warmer or colder climate, create difficulties for the planning age in which we live.
They may be associated with the increased ‘meridionality’ of the general wind circulation, the greater frequency of ‘blocking’, of stationary high and low pressure systems giving prolonged northerly winds in one longitude and southerly winds in another longitude sector in middle latitudes.
The corresponding decline of the westerlies since about 1950 has been illustrated in fig. 17 (p. 53).
Other factors believed to be of importance can be identified in studies which have monitored the global patterns of the wind circulation and the pressure of the atmosphere.
Thus, both the Chilean drought of the 1960s and the strong warming (by about I°C in the overall average) of New Zealand since about 1950 can be linked to a southward shift of the southern hemisphere zone of strongest upper westerly winds and the sub-Antarctic storms and cyclonic activity.
Over both hemispheres there has been more blocking in these years.
Average atmospheric pressure has been higher than in the first half of the century in all latitudes from 67°N to 22–25°N.
It has been lower than before nearer the equator and also in the Arctic except over the areas commonly occupied by blocking anticyclones (near or over northeast Canada and Greenland, northern Europe and northeast Siberia).
The most remarkable feature seems to be an intensification of the cyclonic activity in high latitudes near 70–90°N, all around the northern polar region.
And this presumably has to do with the almost equally remarkable cooling of the Arctic since the 1950s (fig. 96), which has meant an increase in the thermal gradient between high and middle latitudes.
The more complex patterns of the wind circulation which occur when there are stationary anticyclones in parts of the middle latitudes and subpolar zone have been able to produce an increased frequency of the occurrence of cyclonic centres in places in the middle and subtropical latitudes, despite some rise in the overall average pressure level, and increased rainfall in parts of the Mediterranean (notice also the Lisbon record in fig. 92) and much of the southern United States.
The long record of wind and weather patterns over the British Isles (latitudes 50–60°N) shows the twenty-year period 1960–79 as having the greatest frequency of both anti-cyclonic and cyclonic centres over the country since the nineteenth century.
It is presumably a consequence of the enhanced frequency of depression centres passing in these latitudes that counts (from the long series of daily weather maps available here) of the occurrences of gale and storm force wind situations between latitudes 50 and 60°N, over the British Isles and eastern North Atlantic and over the North Sea, show a variation very similar to the global rainfall variability curves in fig. 95b.
The frequencies in the 1960s and 1970s — averaging about thirty days with gale situations a year over the North Sea and 50–55 over the easternmost Atlantic — represent a return to the level of the 1880s and 1890s and the earliest years of this century after 20– 25 per cent lower frequencies in most of the decades in between.
The 1960s and 1970s have also seen an increased frequency of northwesterly and northerly winds in this region (part of the compensation for the fall off of the westerlies, seen in fig. 17), and these have often been strongly developed in the rear of the depressions here discussed.
This seems to account for the increased roughness of the North Sea observed by the German navy.
Indeed, river-gauge observations in the Elbe at Cuxhaven and Hamburg show that the North Sea storm flood frequency in the winter 1972–3 was the greatest since 1792–3, although the flood levels were less severe.
TO BE CONTINUED ...
Such world-wide surveys as have been attempted seem to confirm the increase of variability of temperature and rainfall, as illustrated in figs. 95a and b.
Much the same applies to the atmospheric pressure distribution except that variability was low in the 1950s.
In Europe, as has been noted elsewhere by Professor Flohn and by Dr C.J.E. Schuurmans of the Netherlands meteorological service, there is a curious change in the pattern of variability: from some time between 1940 and 1960 onwards the occurrence of extreme seasons — both as regards temperature and rainfall — has notably increased, while the overall variability as determined largely by the remaining years has been rather lower than in the preceding decades.
Summer is an exception to this and even in Europe shows the more general experience of increased variability.
A world-wide list of the extreme seasons reported since 1960 makes impressive reading.
Among the items included are:
1960–9 Driest decade in central Chile since the 1770s and 1790s.
1962–3 Coldest winter in England since 1740.
1962–5 Driest four-year period in the eastern United States since records began in 1738.
1963–4 Driest winter in England and Wales since 1743; coldest winter over an area from the lower Volga basin and Caspian Sea to the Persian Gulf since 1745.
1965–6 Baltic Sea completely ice-covered.
1968 Arctic sea ice half surrounded Iceland for the first time since 1888.
1968–73 Severest phase thus far of the prolonged drought in the Sahel zone of Africa, surpassing all recorded (twentieth-century) experience.
1971–2 Coldest winter in more than two hundred years of record in parts of eastern European Russia and Turkey: River Tigris frozen over.
1972 Greatest heat wave (in July) in the long records for north Finland and northern Russia.
1973–4 Floods beyond all previous recorded experience stretching across the central Australian desert.
1974–5 Mildest winter in England since 1834. Virtually no ice on the Baltic.
1975–6 Great European drought produced the most severe soil moisture deficit that can be established in the London (Kew) records since 1698.
1975 and Greatest heat waves in the records for Denmark and the 1976 Netherlands and, in some particulars, for England also.
1976–7 Severest winter in the temperature records (which begin in 1738) for the eastern United States.
1978–9 Severest winter and lowest temperatures recorded in two hundred years in parts of northern Europe and perhaps also in the Moscow region. Snowfalls also extreme in some parts of northern Europe.
This shortened list omits most of the notable events reported in these years in the southern hemisphere and other parts of the world where instrument records do not extend so far back.
Cases affecting the intermediate seasons, the springs and autumns, have also been omitted.
These variations, perhaps more than any underlying trend towards a warmer or colder climate, create difficulties for the planning age in which we live.
They may be associated with the increased ‘meridionality’ of the general wind circulation, the greater frequency of ‘blocking’, of stationary high and low pressure systems giving prolonged northerly winds in one longitude and southerly winds in another longitude sector in middle latitudes.
The corresponding decline of the westerlies since about 1950 has been illustrated in fig. 17 (p. 53).
Other factors believed to be of importance can be identified in studies which have monitored the global patterns of the wind circulation and the pressure of the atmosphere.
Thus, both the Chilean drought of the 1960s and the strong warming (by about I°C in the overall average) of New Zealand since about 1950 can be linked to a southward shift of the southern hemisphere zone of strongest upper westerly winds and the sub-Antarctic storms and cyclonic activity.
Over both hemispheres there has been more blocking in these years.
Average atmospheric pressure has been higher than in the first half of the century in all latitudes from 67°N to 22–25°N.
It has been lower than before nearer the equator and also in the Arctic except over the areas commonly occupied by blocking anticyclones (near or over northeast Canada and Greenland, northern Europe and northeast Siberia).
The most remarkable feature seems to be an intensification of the cyclonic activity in high latitudes near 70–90°N, all around the northern polar region.
And this presumably has to do with the almost equally remarkable cooling of the Arctic since the 1950s (fig. 96), which has meant an increase in the thermal gradient between high and middle latitudes.
The more complex patterns of the wind circulation which occur when there are stationary anticyclones in parts of the middle latitudes and subpolar zone have been able to produce an increased frequency of the occurrence of cyclonic centres in places in the middle and subtropical latitudes, despite some rise in the overall average pressure level, and increased rainfall in parts of the Mediterranean (notice also the Lisbon record in fig. 92) and much of the southern United States.
The long record of wind and weather patterns over the British Isles (latitudes 50–60°N) shows the twenty-year period 1960–79 as having the greatest frequency of both anti-cyclonic and cyclonic centres over the country since the nineteenth century.
It is presumably a consequence of the enhanced frequency of depression centres passing in these latitudes that counts (from the long series of daily weather maps available here) of the occurrences of gale and storm force wind situations between latitudes 50 and 60°N, over the British Isles and eastern North Atlantic and over the North Sea, show a variation very similar to the global rainfall variability curves in fig. 95b.
The frequencies in the 1960s and 1970s — averaging about thirty days with gale situations a year over the North Sea and 50–55 over the easternmost Atlantic — represent a return to the level of the 1880s and 1890s and the earliest years of this century after 20– 25 per cent lower frequencies in most of the decades in between.
The 1960s and 1970s have also seen an increased frequency of northwesterly and northerly winds in this region (part of the compensation for the fall off of the westerlies, seen in fig. 17), and these have often been strongly developed in the rear of the depressions here discussed.
This seems to account for the increased roughness of the North Sea observed by the German navy.
Indeed, river-gauge observations in the Elbe at Cuxhaven and Hamburg show that the North Sea storm flood frequency in the winter 1972–3 was the greatest since 1792–3, although the flood levels were less severe.
TO BE CONTINUED ...
Re: CLIMATE, HISTORY AND THE MODERN WORLD
COOLING IN THE ARCTIC
The cooling of the Arctic since 1950–60 has been most marked in the very same regions which experienced the strongest warming in the earlier decades of the present century, namely the central Arctic and northernmost parts of the two great continents remote from the world's oceans but also in the Norwegian—East Greenland Sea.
(In some places, e.g. the Franz Josef Land archipelago near 80°N 50–60°E, the long-term average temperature fell by 3–4°C and the ten-year average winter temperatures became 6–10°C colder in the 1960s as compared with the preceding decades.)
It is clear from Icelandic oceanographic surveys that changes in the ocean currents have been involved.
Indeed a greatly (in the extreme case, ten times) increased flow of the cold East Greenland Current, bringing polar water southwards, has in several years (especially 1968 and 1969, but also 1965, 1975 and 1979) brought more Arctic sea ice to the coasts of Iceland than for fifty years (fig. 97): in April–May 1968 and 1969 the island was half surrounded by the ice, as had not occurred since 1888.
Such ice years have always been dreaded in Iceland’s history because of the depression of summer temperatures and the effects on farm production.
In the 1950s the mean temperature of the summer half year in Iceland had been 7.7°C and the average hay yields were 4.3 tonnes/hectare (with the use of 2.8 kg of nitrogen fertilizer); in the late 1960s with mean temperature 6.8°C the average hay yield was only 3.0 tonnes/hectare (despite the use of 4.8 kg of fertilizer).
The temperature level was dangerously close to the point at which the grass virtually ceases to grow.
The country’s crop of potatoes was similarly reduced.
The 1960s also saw the abandonment of attempts at grain growing in Iceland which had been resumed in the warmer decades of this century after a lapse of some hundreds of years.
At the same time the changes in the ocean have produced changes in the spawning grounds and seasonal range of migration of fish stocks — a not much publicized aspect of the international wrangles and ‘cod wars’ of recent times.
With the fall by over 1°C in the mean sea surface temperatures off west Greenland from the peak years in the 1920s and 1950s, the cod fishery there declined by the early 1970s to a tiny fraction of what it had been in those times.
The Greenland cod migrated to Iceland waters, and for a few years (1967–71) offset the declining stocks there; but since 1974 the spawning stocks in Iceland waters have been only a tenth of what they were in the late 1950s and the total stocks have fallen by almost a half, the decline being probably attributable to combined effects of the change in water climate and over-fishing.
Similarly, herring stocks have moved from Iceland waters to the wider reaches of the Norwegian Sea farther east, south and north and to the North Sea, while a southward shift of the southern limit of cod seems to have led to increased catches in the North Sea since about 1963.
An interruption of the colder regime introduced by the 1960s affected Europe and Iceland, part of east Asia and the eastern United States in the early-mid 1970s and was perhaps too hurriedly hailed as a reversal of the trend.
Most of Europe and parts of the other regions named experienced between 1971 and 1977 four to seven mild winters in a row, largely thanks to repetitive occurrences of anticyclones in positions which gave them southerly or southwesterly winds.
One or two of these winters produced extreme phenomena such as the roses still blooming in the parks in Copenhagen in late January.
But much of the remaining areas of the northern hemisphere, in Asia and Africa and including the polar region and the two great oceans as well as eastern Canada, had a straight run of colder than usual winters in the same years.
As the pattern depended so largely on the positions of stationary (‘blocking’) features in the wind circulation in middle latitudes, no great surprise should have been caused when conditions were reversed again in many of these regions in the immediately following years later in the decade.
By the end of the decade in Iceland, as in other regions of the Arctic fringe, it had to be concluded that the colder regime which set in in the 1960s seems to be continuing; and after notably cold years in 1979 and 1980 the widely debated expectation of global warming setting in as a result of the impact of the man-made increase of carbon dioxide on the world climate is being called in question in these countries.
TO BE CONTINUED ...
The cooling of the Arctic since 1950–60 has been most marked in the very same regions which experienced the strongest warming in the earlier decades of the present century, namely the central Arctic and northernmost parts of the two great continents remote from the world's oceans but also in the Norwegian—East Greenland Sea.
(In some places, e.g. the Franz Josef Land archipelago near 80°N 50–60°E, the long-term average temperature fell by 3–4°C and the ten-year average winter temperatures became 6–10°C colder in the 1960s as compared with the preceding decades.)
It is clear from Icelandic oceanographic surveys that changes in the ocean currents have been involved.
Indeed a greatly (in the extreme case, ten times) increased flow of the cold East Greenland Current, bringing polar water southwards, has in several years (especially 1968 and 1969, but also 1965, 1975 and 1979) brought more Arctic sea ice to the coasts of Iceland than for fifty years (fig. 97): in April–May 1968 and 1969 the island was half surrounded by the ice, as had not occurred since 1888.
Such ice years have always been dreaded in Iceland’s history because of the depression of summer temperatures and the effects on farm production.
In the 1950s the mean temperature of the summer half year in Iceland had been 7.7°C and the average hay yields were 4.3 tonnes/hectare (with the use of 2.8 kg of nitrogen fertilizer); in the late 1960s with mean temperature 6.8°C the average hay yield was only 3.0 tonnes/hectare (despite the use of 4.8 kg of fertilizer).
The temperature level was dangerously close to the point at which the grass virtually ceases to grow.
The country’s crop of potatoes was similarly reduced.
The 1960s also saw the abandonment of attempts at grain growing in Iceland which had been resumed in the warmer decades of this century after a lapse of some hundreds of years.
At the same time the changes in the ocean have produced changes in the spawning grounds and seasonal range of migration of fish stocks — a not much publicized aspect of the international wrangles and ‘cod wars’ of recent times.
With the fall by over 1°C in the mean sea surface temperatures off west Greenland from the peak years in the 1920s and 1950s, the cod fishery there declined by the early 1970s to a tiny fraction of what it had been in those times.
The Greenland cod migrated to Iceland waters, and for a few years (1967–71) offset the declining stocks there; but since 1974 the spawning stocks in Iceland waters have been only a tenth of what they were in the late 1950s and the total stocks have fallen by almost a half, the decline being probably attributable to combined effects of the change in water climate and over-fishing.
Similarly, herring stocks have moved from Iceland waters to the wider reaches of the Norwegian Sea farther east, south and north and to the North Sea, while a southward shift of the southern limit of cod seems to have led to increased catches in the North Sea since about 1963.
An interruption of the colder regime introduced by the 1960s affected Europe and Iceland, part of east Asia and the eastern United States in the early-mid 1970s and was perhaps too hurriedly hailed as a reversal of the trend.
Most of Europe and parts of the other regions named experienced between 1971 and 1977 four to seven mild winters in a row, largely thanks to repetitive occurrences of anticyclones in positions which gave them southerly or southwesterly winds.
One or two of these winters produced extreme phenomena such as the roses still blooming in the parks in Copenhagen in late January.
But much of the remaining areas of the northern hemisphere, in Asia and Africa and including the polar region and the two great oceans as well as eastern Canada, had a straight run of colder than usual winters in the same years.
As the pattern depended so largely on the positions of stationary (‘blocking’) features in the wind circulation in middle latitudes, no great surprise should have been caused when conditions were reversed again in many of these regions in the immediately following years later in the decade.
By the end of the decade in Iceland, as in other regions of the Arctic fringe, it had to be concluded that the colder regime which set in in the 1960s seems to be continuing; and after notably cold years in 1979 and 1980 the widely debated expectation of global warming setting in as a result of the impact of the man-made increase of carbon dioxide on the world climate is being called in question in these countries.
TO BE CONTINUED ...