CLIMATE, HISTORY AND THE MODERN WORLD

thelivyjr
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Re: CLIMATE, HISTORY AND THE MODERN WORLD

Post by thelivyjr » Wed Dec 18, 2019 1:40 p

THE NEED FOR FLEXIBILITY, DIVERSIFICATION AND MARGINS OF SAFETY IN AGRICULTURE AND ENERGY POLICY

We live in a precarious world overshadowed by threats of food and energy shortages as well as nuclear holocaust.

In the most productive countries it now takes two calories of fuel on the farms to produce one calorie of food, and when transport and storage costs are added the ratio may rise to ten or twelve calories of fuel for one of food.


So there is no mistaking the fact that the destabilizing effects of both short-term climatic fluctuations and any long-term change are deeply involved with the more obvious threats named.

We must be prepared to develop our technology in ways that decrease, not increase, the risks.

This may mean avoiding that degree of rationalization in agriculture, aimed at maximum production, which would concentrate too much of the production of one crop in a few areas or which would concentrate the production from one area too much on one crop.

In this respect the very practices which are used today to maximize food production increase the risks of various kinds of disasters.

Apart from the direct effect of adverse weather beyond the supposed extreme occurring in one, two or more years in succession, the possibilities of disaster from plant parasites, which may be encouraged by a certain type of weather, are more serious where monoculture is practised.

An object lesson in this was provided by a newly developed strain of wheat in the Netherlands in the 1950s.

It was a product of scientific plant breeding, which had been carefully tested and found to be resistant to all the then known forms of yellow rust disease.

In 1955, three years after its introduction, over 80 per cent of the wheat sown in Holland was of this variety, Heines VII.

A new variety of the yellow rust appeared and, as a result of its attack, over two-thirds of all the winter wheat sown in this country for the 1956 harvest was destroyed.


The risks of similarly wholesale crop failures — possibly over much wider regions — that would accompany a global warming of the magnitude that some current scientific work suggests could come from the increase of carbon dioxide through increased use of coal, oil and other non-nuclear fuels are no less than the dangers in nuclear waste.

They may even include the same kind of risks, if and when melting of the world's glaciers raises the sea level to the point where nuclear power stations on the often-favoured coastal sites become flooded.

This chapter began with the need for realism and humility about our situation.

We must now stress the needs for diversification, flexibility, and margins of safety in our energy, agriculture, food and population policies.

As Schneider has written:

coal is environmentally damaging, air polluting and may…alter the global climate.

Nuclear power advocates have not fully solved the radioactive waste disposal problem…they have yet to make a reliable assessment of the problem of serious accidents which could release lethal quantities of radioactivity into populated areas.

Wind, hydro and solar power are promising renewable energy alternatives, but each has difficulties….

The only safe projection for energy system planning is…that surprises are sure to come.

This requires flexibility.

One step in that direction is the parallel development of many energy alternatives….

A massive and disproportionate investment in one energy resource….is likely to create an inertia in special interests which will restrict our readiness to react to new information about risks and benefits.

The implications of all this may further require the return of our fashions in architecture and clothing to styles which diminish the demand for fuel of whatever kind.


In the realm of agriculture we must recognize what may be implied by allowing one country to become the world s sole producer of exportable surpluses of basic foods.

For here we glimpse the possible emergence of a new Realpolitik, whereby the producer and holder of available food surpluses in a hungry world could exercise an overwhelming power.

Doubtless there are other risks too, for instance of armed attempts to seize the stocks and dispute that power.

And just as we need margins of safety in the form of planned grain surpluses, and the storing of them safely against the lean years or for emergency aid anywhere, so also grazing lands should not be occupied to the limit — herds should not be allowed to build up to the maximum that can be supported in the best years.

Or, if the land is so occupied, a policy of culling may have to be instituted.

If we wish for a stable world, we must hope to control events so as to break out of the historical cycle of drought and starvation, followed by a buildup of cattle and population during the recovery years to a level which makes it certain that there will be starvation again in the next dry period.

And as Bryson has put a related point:

of course, efforts to increase agricultural production, and distribute food where needed most, and to make human lives more important than profit and power, are worthwhile.

But such measures may only increase the number of people who will starve to death…if the population does not stay below the level of the least food supply that will be all that is available in some years.


We are surrounded by many dangers, but one of the most hopeful things is the progress this century has seen in understanding how human beings and human societies function and how they must be expected to react to their neighbour’s, and to neighbouring nations’, doings.

Nevertheless, the development of an international moral sense lags somewhat behind this growth of knowledge.

In Tickell’s words, ‘no responsible and, still less, elected government could lightly sacrifice a short-term and direct advantage in…wealth and employment for its people to avoid a long-term …and uncertain disadvantage for the human race…as a whole’.

It has been wisely observed that there are already strong incentives for most nations to reduce the consumption of fossil fuels.

Conservation and the development of solar, tidal and wind energy should be given priority over nuclear energy.

Despite the fact that the CO2 emitted per unit of energy produced is 50 per cent higher for coal than oil, there is bound to be a decision to go over to coal from oil wherever possible, as oil reserves dwindle.

So adaption to whatever effects on the climate result is sure to be needed.

It is important now that we also obtain a better understanding of the physical world and its climate and what that should be expected to do, or may do, to the circumstances of our life on this planet.

We should note the words of Lord Zuckerman, OM, FRS on this subject:

in the long history of the Earth we see the shapes of continents and oceans…continually changing; mountain ranges have thrust up to the skies and then disappeared; and ice has covered the land.

We…have a sense of the physical forces that have been at work, but we certainly do not wind the clock which triggers major changes in geography and in climate…these forces are still there;…our Earth is still changing;…the axis on which the globe spins every twenty-four hours is not immutably stable; the orbit in which we move annually around the sun is not constant; …the sun…is itself subject to change; the climate we know — the winds, the rains, the seasons — is also changing from year to year … nature itself has been responsible for far more significant changes in the physical world…than any for which we, the human species, have been or are likely to be responsible.

We should begin to organize, on a world-wide scale, to monitor what is happening.

It would be too late to do anything if, to take an extreme example, part of the ice which covers Greenland…were to break away.

And undoubtedly we would be slow, and even reluctant, to recognize the first signs that anything like that was happening.


TO BE CONTINUED ...

thelivyjr
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Re: CLIMATE, HISTORY AND THE MODERN WORLD

Post by thelivyjr » Fri Dec 20, 2019 1:40 p

THE CHALLENGES OF TODAY AND THE FUTURE: WATCHFULNESS, UNDERSTANDING AND REALISM

The difficulty of recognition of a new trend or a lasting change in the general performance of the climate is real and constitutes an important difficulty for policy-makers.

Such developments are always obscured by the wide range and suddenness of the short-term variations.

It may be that particularly at times of long-term change, the weather ‘slaps about’ from one extreme to the opposite extreme from year to year.


The situation is analogous to the familiar course of seasonal changes in middle and higher latitudes.

As the autumn progresses, the sudden onset of winds from lower latitudes may bring an interval of mild, even summer-like weather.

But the season does change nevertheless and sooner or later makes itself known.

Perhaps, in one regard the smallness of man's powers in relation to those of the natural world even today is a matter to be thankful for.

The list of ideas for climatic and other types of warfare by altering the environment is a frightening one.


But the experiments of the 1970s in defoliating forests, interfering with the monsoons of Asia, and ruining crops, seem to have had results which fell far short of expectation.

A fringe activity of a more positive kind, which has long been considered as a possible source of supply of fresh water for arid lands near the sea, is to tow icebergs from the Antarctic.

Small bergs were occasionally towed north from southern Chile to the drier parts of the country in the 1890s and even as far as Callao in Peru (latitude 12°S).

But more recently operation on a bigger scale has been advocated, towing some of the huge tabular icebergs which calve off from the Antarctic ice-cap, sometimes individually as much as 10–100 km long and deep enough to strand in 40–60 m of water, to the desert lands in the Middle East.

However, indications so far are that 50 per cent of such a berg would melt away on a journey to even the easiest destinations, while the cracks and crevasses that are nearly always present would threaten break-up and total loss of the berg on the way and its overturning (as is usual in such developments) would endanger the towing vessels.

The effectiveness of artificial seeding of clouds to produce rain, to forestall hail or clear the cloud, has remained debatable or at most has had success on only a local scale.

Man’s history has been played out in an ever-changing world, the changes sometimes slow, sometimes fast, the nature of the long-term ones always obscured by the bigger swings that distinguish the individual years.

The environment will continue to change, partly due to human activities with their effects both intentional and unintentional, and partly due to natural causes.

There is certainly no warrant in this for expecting that either a constant or an ever-rising standard of living will in the long run be possible.


But we can with good reason continue to seek a juster world in which the poor and vulnerable — both individuals and nations — are less and less disadvantaged.

There is encouragement, too, in that people in every generation, even amidst the discomforts and hardships of primitive times, have found their joys and happiness.

Those in middle latitudes have thanked their gods for the green Earth, the lilies of the field and the golden corn, those in other latitudes for the beauty of the polar and mountain snows, the shelter of the northern forests, the great arch of the desert sky, or the big trees and flowers of the equatorial forest.

How many of our present problems arise from not understanding our environment and making unrealistic demands upon it?

This book has presented human history as a climatologist sees it.

The climate seems to have had many effects; though seldom a determinant of human history, its influence on the overall picture of society may be great.


Again and again the development of climate seems to enter in as a destabilizer and catalyst of change.

Adaptability and flexibility in our planning in the face of climatic and environmental change may in extreme situations be the price of survival.

It has even been argued that the demise of the old European colony in Greenland in the late Middle Ages was due not so much to the increasing difficulty of the climate as to the colonists’ failure either to go over to an Eskimo way of life or to evacuate the country.

But it is important also to note the lessons in history that by the time when climatic stresses become severe the people at risk tend to lose their power, or their willingness, to adapt and with it lose their resilience.

The world of human idealism, the faith of the Christian believer and other devoted people, and the sympathies of the humanist will for ever be engaged with a changing scene and must rise to meet ever new challenges.

And our actions need the best assessment of the development of the physical world about us, and the likely effects of any course of human action impinging on the natural world, that science can bring.


TO BE CONTINUED ...

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Re: CLIMATE, HISTORY AND THE MODERN WORLD

Post by thelivyjr » Fri Dec 20, 2019 1:40 p

RECENT DEVELOPMENTS AND THE OUTLOOK

THE MID-TWENTIETH-CENTURY COOLING


The lowering of world temperatures from the 1930s and 1940s to some time between 1975–80 and 1985 has been less than the rise over the previous fifty years.

Hence, the twentieth century has been warmer than the previous two centuries.


This is a broad summary statement that is generally true the world over.

However, estimating average temperatures for the whole Earth to something approximating the degree of precision claimed (or, at least, generally implied) by figures now commonly published can surely never be realistic because of the huge ocean spaces — about 70 per cent of the surface of the globe — and the local diversity of soils and drainage, etc. on land, not to mention the error margins to which all sensing methods are liable.

In central England the 1900–93 average temperature is 0.8°C above that which Manley derived from the late seventeenth century (1659–99) and 0.3°C above the figures for the eighteenth and nineteenth centuries.

Despite the remarkable warmth in 1989 to 1990 (years which in England were however not significantly warmer than 1948 and 1949), no later decade has so far equalled the average for the 1940s or for the 1930s and 1940s combined.

This position may not be true for Scotland and Scandinavia, where heavily predominant west and southwest winds made the years from about 1987 to 1991 outstandingly warm.

We still need more knowledge and understanding of the variations, which in some cases evidently last up to several decades, in the correspondence (or lack of it) between the temperature trends in different latitude zones and other fairly large regions.

As pointed out on p.39, there were times during the Little Ice Age period in recent past centuries when the climate of the Antarctic became relatively milder, at least round a wide fringe zone, just when some of the coldest phases were being experienced in the middle and higher latitudes of the northern hemisphere.

From 1950 to the 1990s the world situation has approximated to the reverse of that pattern.

The North Polar basin and, especially, a region extending south from there as far as Iceland, has tended to be out of step with much — perhaps most — of the rest of the world.

A count of the number of months each year when most of the polar cap north of 70° was warmer, or colder, than the 1931–60 average showed a preponderance of cold months in every year from 1960 to 1986, mostly a fourfold preponderance (see fig. 96, p. 270).


Taking the world baldly as a whole, there is no doubt that the twentieth century has been a warm time.

We have to take note that at times some large areas may be out of step, as in the recent examples we have quoted in these paragraphs and as, indeed, China seems to have been (see p. 171) during much of the Middle Ages, when Europe and much of the Arctic had a warm epoch.

It has been suggested that such asymmetric patterns around a hemisphere may be linked to the known wanderings of the magnetic poles of the Earth as a result of changed targeting of the corpuscular streams of radiation from the sun.

No physically complete explanation seems, however, to have been presented.

Another asymmetry, in the development of the seasonal round, has been noticeable in the later half of the twentieth century: the autumns in the northern hemisphere, particularly the Octobers, continued at, or near, their warmest level through the 1960s, 1970s and 1980s, even when the other seasons, particularly the springs, became colder.

This last item is mentioned here chiefly as a warning against expecting too simple patterns.

No doubt a physical explanation would involve understanding changes in the latitudes occupied by the jet stream and the average strength of the wind circulation, as well as more localized controls of where the main energy sources and the strongest flow lies, and perhaps such external matters as the solar constant.

Since around 1980, international concern about the environment and the possibility of disastrous changes to the climate, to the atmosphere which we breathe and to the Earth's surface, as an outcome of the ever-increasing scale of mankind’s intrusions and pollution of many kinds, has been continually increasing.

Prospects of global warming are now spoken of on every side and are treated by many, including people whose decisions affect millions, as if the more alarming forecasts were already established fact.


Let us consider some facts which lie deep in the framework of what we have to consider.

TO BE CONTINUED ...

thelivyjr
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Re: CLIMATE, HISTORY AND THE MODERN WORLD

Post by thelivyjr » Sat Dec 21, 2019 1:40 p

THE UNRELENTING GROWTH OF THE WORLD’S HUMAN POPULATION

This is the biggest of all the threats to life on Earth and is responsible for many of the other threats.

And it ensures that the consequences of climatic changes and variations, which occur all the time, will thrust far deeper into the lives of people and be harder to adjust to.


The Irish potato famine in the 1840s, already referred to (see pp. 252–3) provides an object lesson.

It was surely the most horrifying example in Europe of a well-documented climatic disaster — in this case simply caused by a run of warm, moist summers — which had become certain to happen whenever the appropriate weather occurred.

Its consequences were greatly aggravated by the fast-growing overpopulation.

Ireland’s rural population had been multiplying, having probably doubled from 1820 to the mid-1840s.

By that time the potato was the only crop that could produce the bulk of food needed to fill the peoples bellies.

And the cheap ‘lumper’ variety, which was inevitably mostly chosen, proved particularly vulnerable to the blight.

The farmers’ holdings were commonly only one to 1 1/2 or 2 hectares, as a result of repeated subdivision among the inheritors in successive generations: this process could go no further.

The historian, Robert Kee, writing of this famine, tells of the pitiful scenes that followed of disease and death, as well as the packed emigrant ships on which more died, and, probably inevitably, the lasting sense of outrage and resentment that it bred.

He adds: ‘it is easy now to say that the accusations of genocide made by some Irish writers at that time and since were unjust …the government [in London] was the prisoner of the economic philosophy of the day which taught that economic laws had a natural operation’ and to interfere…would bring chaos.

In fact, ‘the government looked on with…increasing dismay at what it regarded as its helplessness before irresistible economic and social forces’.

And he goes on, in the end, ‘by what seemed a superhuman effort at the time, it succeeded in abandoning …some of the principles it held most sacred and brought itself to distribute government charity’.

Such are the dilemmas faced whenever natural trends bring new, but urgent and distressful, situations and such are the hesitations and delays that characteristically hinder helpful action by the authorities.

The divisive human reactions among those affected are also predictable, as we can now see from more recent events in other parts of the world.

Other possible climatic developments now before us threaten difficulties of no less magnitude.

TO BE CONTINUED ...

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Re: CLIMATE, HISTORY AND THE MODERN WORLD

Post by thelivyjr » Sat Dec 21, 2019 1:40 p

THE MORE OR LESS WORLD-WIDE WARMTH OF THE TWENTIETH CENTURY, EXCEEDING THAT OF MOST RECENT CENTURIES

The warming generally seems to have begun around 1700 and has gone through a number of rapid phases as well as some sharp setbacks, one of which between about 1780 and 1850 brought things back to more or less as they were before it.

It seems that a number of different factors have contributed to the sequence, among them variations in the amount of volcanic activity which loads the atmosphere with dust, gases and vapours that may still be carried and veil the suns radiation for some years after the greatest eruptions, as well as the larger sizes of debris that soon fall out.

The strength and constitution of the solar beam itself are also subject to some variations.

And changes in the amount of carbon dioxide and other ‘greenhouse gases’ in the atmosphere, as well as variations of the water vapour content, and of cloudiness, must also be expected to affect the climate.

It now seems necessary to admit — though this is seldom mentioned in recent literature — that none of these variations explains the timing of the general warming and cooling phases altogether satisfactorily, certainly not as well as widely claimed.

In particular, the onset of the sharp warming phase around 1700, and the mid-twentieth-century cooling from about the 1940s to the early 1980s, are not well accounted for.

Nor is the magnitude, nor the distribution, of warming and cooling over the Earth in good agreement with most global warming model predictions.


Even the great warmth of the years 1989–91, hailed in some quarters as proof of the reality of the predicted global warming due to the enhancement of the greenhouse effect by increasing carbon dioxide and other effluents, requires the usual adjustments.

But it may also have a surprising analogy in the past to the remarkable warmth — well attested in Europe — of the year 1540, shortly before the sharpest onset of the so-called Little Ice Age.

Pfister records that for several decades before 1564 the climate in Switzerland — and this seems to be in line with the implications of other European chronicles — was on average about 0.4°C warmer, and slightly drier, than today.

The summers in the 1530s were at least as warm as in the warmest ten years of the present century, between 1943 and 1952.

And the year 1540 outdid the warm dry year 1947 appreciably.


From February till mid-December 1540 rain fell in Basle on only ten days.

And young people were still bathing in the Rhine on the Swiss-German border at Schaffhausen in the first week of January 1541 after a ten-months-long bathing season.

The warm anomaly of 1540 is the more remarkable because the weather then became severely wintry, and spring came late in 1541.

Moreover, only twenty-four years later the 1564–5 winter was one of the longest and severest in the whole millennium in most parts of Europe and marked the arrival of the most notable cold climate period of the Little Ice Age, with ten to twenty historic winters, very late springs, cool summers and advancing glaciers.


TO BE CONTINUED ...

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Re: CLIMATE, HISTORY AND THE MODERN WORLD

Post by thelivyjr » Mon Dec 23, 2019 1:40 p

THE DEVELOPING OZONE HOLES

Ozone is created in the upper atmosphere at heights near 50 km above the Earth's surface by the action of the sun's ultra-violet radiation on the oxygen molecules and free oxygen atoms at those heights.

The process absorbs this lethal (UV) constituent of the sun’s rays.

The ozone diffuses downwards and reaches its greatest concentration in the layers between 15 and 50 km, especially between 15 and 30 km, at one to ten parts per million.


At lower levels the ozone (O3) molecules become dissociated as they oxidize things they come in contact with, and this action leaves ordinary oxygen (O2) molecules once more in the atmosphere.

The ozone in the stratosphere, like the volcanic eruption products that occasionally reach those levels, is gradually carried polewards.

It reaches its greatest concentration over high latitudes, but near the jet stream it leaks downwards into the lower atmosphere and is destroyed.


The absorption of some of the sun's short-wave radiation in the process of forming the ozone warms the stratosphere at the levels where it takes place.

Destruction of the ozone in the atmosphere by chemically active agents released in the exhausts of high-flying aircraft and rockets or space-ships, as well as from household use of aerosol sprays and from refrigerators, which are — however surprisingly — found to reach the stratosphere, is now a major cause of anxiety, no less than other forms of pollution.

It was first noticed in 1984 over the Antarctic, where substantial depletion of the ozone was discovered in the core region of the stratospheric circulation during the winter night.


This has been observed again and again in every year since, and the area affected has grown bigger.

By 1992, the extent of the ‘hole’ in the ozone layer over the Antarctic at its seasonal maximum was about four and half times what it was in 1984.

A similar feature has since appeared over the Arctic as well during the northern winters.

And when the winter stratospheric circulation regime is approaching its end, these features wander far enough from their origin to expose some areas in the inhabited temperate latitudes for a time to solar radiation from which the harmful ultra-violet rays have not been filtered out by passing through the ozone layer.

This now regularly repeated destruction of the protective ozone layer demands modification of fashionable and popular habits that almost universally have become part of the twentieth-century way of life.

Exposure to the sun must be severely limited, and dress modified accordingly, if skin cancers and other undesirable effects are to be avoided.

Another issue is that loss of the ozone layer may be expected to reduce heating of the stratosphere and contribute to warming the lower atmosphere layers that we inhabit.


TO BE CONTINUED ...

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Re: CLIMATE, HISTORY AND THE MODERN WORLD

Post by thelivyjr » Mon Dec 23, 2019 1:40 p

POLLUTION

Humanity is continually polluting the atmosphere in various ways.

The sulphur dioxide (SO2) released by burning coal, gas and oil in industrial processes and in domestic fires is the cause of many anxieties, from creating breathing problems to turning the rain acid.


Acid rain, reported now in many regions of the world, damages plant life — sometimes killing the trees (even whole forests) — ruining the soil and poisoning lakes and other water bodies.

Sometimes all the fish die.

The carbon dioxide (CO2), which is the chief product of burning all fossil fuels, wood and cut vegetation, is added to the atmosphere.

The small proportion of CO2 in the air has increased from 260 to 280 parts per million in the mid-nineteenth century to about 350 ppm today.

The carbon dioxide in the atmosphere is the basic food of vegetation, which may be expected to grow more luxuriantly in a more carbon-rich environment.

If climates get warmer, it should benefit from that too.

The atmosphere's carbon dioxide is expected to increase to about 600 ppm by the year 2100, which, if it occurs, must be expected to alter the balance of radiation passing through the atmosphere and is generally expected to warm the climate significantly – according to some forecasts to a temperature level that has not occurred for many millions of years.

Much research published in recent years has been directed at anticipating the increased crop yields that might be expected in a warmer world and the possibilities which might open up of growing warmth-demanding crops in new areas.

But against these advantages must be set the likely extended ranges of insect pests and diseases from warmer latitudes.

However, the match between past periods of increasing CO2 and climatic warming seems not to be as close as expected and widely claimed.


Worst of all the types of pollution is the accumulation of nuclear waste materials on or in the ground and the decay products in the atmosphere and terrestrial environment.

DDT that must have come from insect sprays used in the main inhabited countries of the world has been found in the snows of Antarctica, and radioactive caesium from the nuclear plants at Sellafield (Windscale) in northwest England has been found in the sea surface water in the polar ocean current moving south off the coast of East Greenland.

The range of consequential threats has been illustrated by the contamination of sheep in England, Wales and Scotland with wind-borne radioactive matter from the accident at the nuclear electricity plants at Chernobyl in the Ukraine in 1986.

Over eight years later the contamination still persists in some of the areas across Europe reached by this fall-out.


Similar nuclear accidents have occurred elsewhere, as at Three Mile Island in the eastern United States in 1980, and more must be expected in the future.

There is nowhere near the surface of the Earth where radioactive nuclear wastes can be stored indefinitely without risk of dispersal at some later date by earthquake, volcanic activity or war.

TO BE CONTINUED ...

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Re: CLIMATE, HISTORY AND THE MODERN WORLD

Post by thelivyjr » Mon Dec 23, 2019 1:40 p

WINDINESS AND STORMS

There have been indications in many regions, seemingly representative of most of the Earth, that windiness — as shown, for instance, by average wind speeds and the frequency of storm winds — has been increasing since about 1950.

Flohn and others have argued, surely soundly, that this can logically be associated with the undoubted rise of ocean surface temperatures over these years, principally in the tropics and in the higher southern latitudes.

This has been accompanied by an increase of the area in the warmest tropical oceans with surface water temperature above 27.5 °C, which seems to be critical for tropical hurricane formation.

These authors also mention the doubt entertained by several leading investigators about attributing the twentieth-century warming mainly to the increase of ‘greenhouse gases’ in the atmosphere.

Care must certainly be exercised before attributing the increase of general windiness to global warmth, since there seem to have been stormier and less stormy periods in the past which cannot simply be aligned with warmer and colder periods respectively.


(A possible counter-argument would be available if it could be shown that in past cold episodes which were, or are, regarded as stormy, the storminess was narrowly restricted to some particular zone.)

The present (1990s) warmth of the tropical oceans, on average warmed by about 0.3°C over the last thirty to thirty-five years, can safely be presumed to have been accompanied by increased evaporation from their surface.

There is indeed indirect evidence of an increase of rainfall over those oceans in a measured reduction of the salinity of the surface waters.

(Rainfall at sea cannot yet be directly measured reliably.)

And it must be safe to conclude that the overall water vapour content of the Earth’s atmosphere has been increased in consequence.

More latent heat must therefore have been released by condensation of this water vapour in clouds.

In this way, the total energy of the world’s winds and weather systems must have been increased.


Flohn estimates the overall intensification of the general wind circulation by these processes over recent years at probably 10–12 per cent of the energy budget.

And he points to the implication that more extreme weather systems and events should therefore be expected: ‘more severe cyclones and hurricanes…very heavy precipitation and intense hail-storms, but also (at least to a more minor extent) more active subsiding air motion in anticyclones’.

The semi-permanent centres of low pressure over the northern North Atlantic and northern North Pacific have shown this expected intensification.

But there is doubt as to how far this can be due to global warming from the man-made increase of carbon dioxide and other ‘greenhouse gases’.

Doubts arise because the geographical distribution of the warming differs markedly from model predictions.

It is not as marked in the Arctic as in some other regions.

And the prolonged cooling period between about the 1940s and 1975–80 or after coincided with a time when the increase of carbon dioxide, etc., was more rapid than ever before.


The warmth noted over much of the northern hemisphere, particularly Europe, the European Arctic, Greenland and North America during the high Middle Ages does seem to have led to a very notably stormy period (see pp. 191–4), at least in the North Atlantic and European sector, around its closing stages, particularly in the 1200s AD.

But we have noticed elsewhere in this book (e.g. pp. 218–19) evidence of another climax of storms and blowing sand at the coasts of Europe coinciding more or less with the coldest climate period between about 1550 and the 1720s or after.

In Britain, as in other places near the Atlantic fringe of the continent of Europe from northwest France to Norway, the storm which struck on 15–16 October 1987 was certainly one of the severest in the last three hundred years or more, generally thought to be comparable with the famous storm in 1703 (see p. 219) which was very fully described by Daniel Defoe.

The strongest gusts of wind in the 1987 storm ranged up to 119 knots (220 km/hr) at the coast of Brittany.


There was enormous damage to forests and woodland.

Traffic was halted for many hours in all the countries near the path of the storm.

Insurance losses from damage, chiefly to buildings and trees, in England alone was estimated at £1,000 million at 1988 prices, but the number of people killed (eighteen in England) was not very great, as the worst of the storm was in the night hours.

The trend over recent decades to increasing storminess has produced new records for low pressure over the Atlantic.

Older texts on climate reported that barometric pressures over the North Atlantic corrected to sea level had been known to go down to about 925 mb, although values below 940 mb were very rare.

Nevertheless, in the winter of 1982–3 three depressions deepened to between 930 and 934 mb and these figures were repeated by two more North Atlantic lows in November 1992.

On 15 December 1986 a centre between southernmost Greenland and Iceland had a pressure value of 916 mb and on 10 January 1993 another case, with central pressure as low as 912 to 915 mb, occurred close to southeast Iceland, near 62°N 15°W.


A count made in the Deutsche Seewarte, Hamburg, of the numbers of lows attaining depths below 950 mb on the North Atlantic, winter by winter since the late 1950s, produced the following average figures per winter: 1956–9 (4 winters) average 5 to 6 per winter; 1960–4 average 3 to 4; 1965–9 average 1.2; 1970–4 average 5.2; 1975–9 average 5.6; 1980–4 average 5.4; 1985–9 average 5.6; 1990–1 (2 winters) average 15.5.

Some remarkable wind strengths have been experienced.

Indeed, an extreme gust of about 174 knots was allegedly measured just north of Shetland on 1 January 1992 in another storm that produced a measured gust strength of 119 knots at Ålesund on the west coast of Norway and £35–40 million damage in that country with great destruction in the forests as well as to shipping and coastal installations.

TO BE CONTINUED ...

thelivyjr
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Re: CLIMATE, HISTORY AND THE MODERN WORLD

Post by thelivyjr » Tue Dec 24, 2019 1:40 p

RECURRING OSCILLATIONS IN LARGE-SCALE WEATHER PATTERNS

The most important of these, both introduced in chapter 3, are the Southern Oscillation (see p. 48) and the development of ‘blocking’ of the middle latitudes westerlies by slow-moving or stationary high pressure systems (pp. 36, 55).

Neither is a regular oscillation with constant period.

We reported on p. 306 the wide-scale regional anomalies that develop in the world's climate with, and after, the greater than usual magnitude of the swing of the ocean currents and sea temperatures in the broad Pacific Ocean in 1972, a familiar pattern to the coast dwellers and fishermen of Peru as ‘El Niño’.

This occurs at intervals of about two to seven years.

It affects the very cool Humboldt Current that normally brings water from southern temperate latitudes north all the way along the coast of South America to Peru, where it further draws up cold bottom water as it begins to turn away from the coast to proceed west across the ocean near the equator.

The El Niño, interrupting this normal regime, most characteristically begins to be noticeable about Christmas time — the Spanish name means ‘the baby’ — and develops during the months that follow.

It is now understood to be an integral part of the great Southern Oscillation (q.v.) so that some meteorologists (and accounts of it in the literature) now prefer to rename
both — in the regrettably obscurantist fashion of these times — as ENSO (El Niño —Southern Oscillation).

The normally prevailing ocean currents in the region make the waters near the Peru coast, and some way from there across the Pacific, the coldest sea surface in the world at such latitudes, with temperatures around, or below, 20°C and occasionally as low as 16°.

During El Niño events, this pattern is replaced by warmer water with temperatures normal for the equator spreading from the north.

The fisheries are, of course, affected.


The meteorological consequences include very much higher rainfall than in other years in Peru and the Pacific islands.

But, through the much wider range of the Southern Oscillation, this is linked with anomalies extending to the occurrence of blocking anti-cyclones (and easterly winds) over the higher middle latitudes (sometimes) in both hemispheres.

Our account on pp. 306–8 mentions the economic and cultural disasters that were associated with the great 1972 El Niño, when sea surface temperatures west of Peru, which had been 2–2.5°C below normal about New Year, rose to 3.5–4° C above normal from June to the following December.

There was another, briefer and less intense, El Niño in 1976–7.

But the next one, in 1982–3, was an even greater and longer-lasting El Niño, perhaps matching that reported in 1877.


(No other comparable case is known from the period for which we have instrument measurements.)

Sea surface temperatures off the coast of Peru rose up to 7°C above normal in June 1983.

The impacts on human affairs in many countries were much as in 1972.

One place in northern Peru had 3950 mm of rain between November 1982 and June 1983, compared with 25 mm twelve months earlier.

This situation was followed by other extremes.

The most striking of these was the most extreme phase of the drought (and consequent famine) that has affected the Sahel-Ethiopian zone of Africa since the late 1960s.

This has made its mark on enormous numbers of people all over the world through the emergency appeals and relief work in Africa by all the leading charities, and popularized by the ‘Band Aid’ and ‘Food Aid’ activities in 1985 and since.


There is a ‘Southern Oscillation Index’, defined as the difference of monthly mean barometric pressure between Tahiti in the Pacific and Darwin in northern Australia.

It indicates the relative strengths of the South Pacific subtropical anticyclone and the winds in the equatorial convergence zone over the Indian Ocean.

In the normal climate situation this Index has positive values, but during El Niño events the values are consistently negative.

In 1983 the greatest negative values of the century occurred.

Extreme occurrences such as this may damp out the trend of climate or may even be able to switch it into a new course.

Handler maintains that El Niño and Southern Oscillation events are liable to be linked to the distribution of volcanic aerosols in the atmosphere over the northern and southern hemispheres after great eruptions.

CONCLUDED ...

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