THE WEATHER

Rotorua Morning Post, Volume 3, Issue 700, 28 November 1933, Page 3

THE WEATHER

WHAT SUMMER MEANS ACTION OF THE SUN SPOILT BY DISCHARGE OF VOLCANIC DUST. "BRIGHT INTERVALS." Wlhat is happening to our weather? asks Sir Napier Shaw, formerly director of the London Meteorological ' Office, in the Daily Mail. ' First, what do we mean by our " weather, and in what sense is it ours ? Let us s,ay that we are thinking ; ahout the normal sequence of wea'ther in ,the course of the year — rainfall, snowfall, temperature, sunshine, winds, cloud, fog, etc., over our London, or our England and Wales, our Great Bxntain or our British Isles, our ' Europe, our Northern H'emisphere, j'or our glohe. j The "normal sequence" is what we ; arrive at by taking the aver,ages — ' ; daily, weekly, monthly, or seasonal — [ of the various elements of weather as | recorded over a long series of years. Thirty-hve years is generally a favourite period for a normal, and the one thing that is quite certain about •these normals, or averages, is that there never was a year in which the InoiTOal sequence was the actual, and there never will be one so long as we are on this planet. The study of i climate is essentially the study of change. The year never repaats itself and the nornxal never repeats itself; but there is a French proverb, "Plus ea change, plus c'est la meme chose." ' 'So it is with the experience of our climate; one year is never the same ' as the year before or the year after. But there is a likeness about them, an ideal which may be regarded as * characteristic of the locality, an ideal which might even enable us to draw a distinctioon between the Riviera and the Cornish Riviera. 1 'Changes are gradual, and when we think about changes of climate we 1 must distinguish between those which occur in a lifetime, or within a cen- - tury, oi*, again, within historical times, and those within twenty thousand or a million years. Modern Invention. ' With an unlimited time scale we ' might have a time-table something ' like this: 40,000-18,000 B.C., last gla'cial period; 18,000-12,000, beginning of neolithic civilisation; 800, mud deposit of the Nile hegun; 1800, beginning of the classical pei*iod of rainy ' seasons;. 400 B.C., maximum of the rainy seasons; A.D". 400, eiid of the ' classical period of great rainfallj ' 1300-1400, century of violent storms and extremes ; 1434, last maximum of storminess. But numerical noi'mals are modern : inventions. Instruments are needed to establisb them. If we 'go back beyond the eighteentb cenmry we have to trust to other indications of climate and its changes. That is what makes the subject so interesting. We have to take out of history the information about droughts and floods and famines and try to interpret them in the light of the average of our experience. • E. J. Lowe did this years ago in :a hook, Otto Petterson in a paper before the Mjeteorofogical Society, Sir Richard Gregory in a presidential address, and Sir W. Beveridge in a discussion of wheat prices at the British Association. Then we have to settle what pai't of the world we are thinking about. The rings of growth' of the Sequoias of California (which we call Wel-

lingtonias), discussed by A. E. Douglass, give us continuous records for 3000 years, in which we think we can identify wet periods and dry periods — fhough not for "our" climate. The ruins,. of cities -like Palmyra, in the Syrian Desert, suggest to- us changes of climate that we should not like to face. Wihen it is Europe that is under consideration the geologists, led by Baron de Geer, of Sweden, trace for us the gradual progress of climatic change from the last Ice Age to the present day. They tell us that vast areas of this country wcre covered with ice 18,000 years ago and— iconfirming the suggestion made by Aristotle more than 2000 years ago — (that what is now land was formerly under the sea, and they even suggest that the present distribution of land and sea is to be accounted for by frag- ' ments of one original great land mass floating in fluid strata and ' drifting northward and westward away from their orginal companions. I have even heard it suggested that a time may come when Ir eland, which h'as been geographically adrift fronx Great Britain for a few_ million years, will beeome the near neighbour of the United States. A celehrated' hymn writer wrote, "Change and decay in all around I see." In another frame of mind he might have seen "re-form" (the hyphen is important) in stead of decay. Some investigators find the i changes in our climate periodic, meaning that, roughly speaking, the conditions . recur time after time with ,a definite interval between recurrence. • From informatien about the levels ■ of the great rivers, ahout vintages and other crops, Professor Bruekner made out a period of 35 years, which Francis Bacon had already thought worthy of investigati-on for the Low •Countries. Another Favourite. Eleven years forrn another favourite period, which agrees, plso roughly speaking, with the period of frequency of visihle spots on the sun. In this connection we may remember that the notably fine summers of the ■ present century are thcse of 1911, 1921 and 1933— (three fine summers within 33 years. Here, while we are thinking of the sun as making our summers, let us not forget that the earth h'as a trick r 0f spoiling the sun's effort for months and sometimes years, by discharging dust into the atmosphere from its volcanoes. In 1912, up to the month ' of Miay, the promise of a fine year was strongly upheld. . Then came an eruption of Katmai, an Alaskan volcano, which spoiled the summer for ' Europe. So marked, indeed, has been the e£-

'fect of volcanic dust that 5r°fessor 'W. J. Humphreys has regarded it as an important climatic influence. This may indeed be s,aid: that the -last summer in England has really ibeen remarkable for the character of what the forecaster calls "bright intervals" as well as for its intrusion upon our treasured "normals." iSince last November up to the end of July, taking Cambridge as an example, the weather has been 430 daydegrees up on warmth, 160 hours on sunshine, and down 4in on rainfall. During August and September the . i position has been notably exaggerated. And so far as personal observation is evidence, there has heen a striking display of intensity of sunshine during the bright intervals. It may he that our atnxosphere has been exceptionally free from the dust •of volcanoes, as well as from the smoke of our towns, or perhaps le roi soleil has heen making a sp-ecial effort in recognition of the worship that has been offered to: him by the myriad sunbathers of our era. It is possible that the expert of five hundred years hence will be able to say that our weather, as we know it to-day, has undergone some changes. But these changes, or trends inother directions, certainly cannot be determined hex*e and now. As for next year's weather — in which' we are perhaps more immediately interested — we still have to wait for principles by which it can be estimated.