"PAST CLIMATES"

Rotorua Morning Post, Volume 2, Issue 241, 1 June 1932, Page 8

"PAST CLIMATES"

| ice ages ! INTERESTING LECTURE BY DOCTOR KIDSON. METEOROLOGICAL CHANGES. j - -f y -• In diseussing "Past Climates," the subject of an adchjess to the "Wellington Philosophical Society, Dr. E. Kidson said that he was not going to refer to those changes which most people of mature age Tpelieve to have taken place within their own lifatime. "These," he remarked, "are of two principal kinds. In the first, the individual has heen impressed at an early age by a few or frequently even only one season of a certain type. This becomes established in his mind as the normal season and when later he has to recognise that otber types frequently occur, he coneludes that the climate is changing. It may be that there is more wind, on the average, than he had believed, or the ratio of north-westerlies to southerlies is different. The second kipd arises from our increased susceptibility to eold as we grow older. Most middle-aged people are convinced that the climate has become colder."

N.Z. Fluctuations. The fluctuations in climate in New Zealand sinee the coming of the white man had been very slight, Dr. Kidson pointed out, and it was impossible to recognise any general trand. In the civilised world as a whole, however, r there had been definite fluctuations of climate during the past 2000 years. Amongst the most interesting and most definite pieces of evidence were, perhaps, the great changes in the depth of the Caspian Sea and the recent discovery of graves in Greenland in ground which is now permanently frozen. Not only must the ground have been soft to permit the burial, but the coffins have been punctured by plant roots, indicating that temperatures must have been much milder in the 10th century than at present. "But any changes it has been possible ' to identify will certainly have been | comparatively unimportant. For a ' period of ten years, say, the climate in a particular area may be unusually wet, only to return again to normal. Or the mean temperatures may be slightly above the averags or the winters unusually cold. But though many writers have described what they record as evidences of a progressive desiccation of the world, it is extremely difficult to prove that the fluctuations discovered have been simultaneous in, for instance, Europe and eastern Asia or America. Much of the evidence has been discounted by geologists and geographers. Indeed, the present tendency is for investigators in all lines to minimise the past climatic variations which had been propounded by previous investigators. , In the Distant Past. "When, however, it is a question of 10,000 years and more back, the case is very different. lln past geological ages there have undoubtedly been climatic changes of great magnitude and | probably of world-wide extent." These , changes in past geological ages Dr. ' Kidson discussed at length, bringing to the notice of his audiencs some of the ideas recently developed by Dr. G. C. Simpson, Director of the London Meteorological Ofiice, which have attracted a considerable amount of attention and, apparently, won considerable approbation. The following, said Dr. Kidson, were perhaps the most outstanding climatic variations found by geological evidence to have occurred in past times and the ones which any theories of the causes of climatic variations have to account: — (1) There was extensive j glaciation in the late carboniferous j period in the Southern Hemisphens, I while land ice extended right down to sea-Ievel at many places in equatorial regions. There ^as complete evidence of the existence of large ice sheets, for instance, in Australia, South Africa, and South America, while glaciers flowed down to the sea in India. At the same time Europe and high northern latitudes appeared to have enjoyed more temperate if not sub-tro-pical conditions. (2) In much of the Mesozoic era and on into the Eocene the climate in all parts of the world appeared to have been much more uniform than at present, and temperatures in high latitudes much higher (3) Finally, we had that most impressive event in climatic history, the Pleistocene Glaciation. "Even in New Zealand, the evidences of this glaciation are most striking. Existing glaciers were much more extensive, while many areas now free of ice were then glacified. The sub-Ant-arctic islands carried extensive glaciers. In Europe and America the evi- j dences of this glaciation ara very | complete, and it has been proved to j have been not one glaciation but seve- ' ral, with interglacial periods, some of which at least were warrn and moist. The relative completeness of the evidence makes this glaciation the best test of the numerous theories regarding climatic change." j $> | Why Climates Change. j The leeturer than discussed meteorological principles and the various theories advanced as to the causes of r climatic changes. Amongst the hypotheses examined were those which attributed climatic changes to changes in the motion of the earth as a whole, orbit and the inelination of its axis of rotation to -the ecliptic. Changes in the composition ^of the atmosphere and oceans, changes in topography, changes in the sun's radiation, changes in the internal heat of the, earth, and the passage of the solar system through cold regions of space, were all criticaliy .examined as causes of change of climate. Dr. Simpson's ideas were explained, the leeturer in- [ timating that Dr. Simpson chiefly favoured the theories of topographieal change", including continjental drift, and of variations in solar radiation. From the arguments advanced by him, concluded Dr. Kidson, it would appear that we are now living in a cold inter-glacial epoch. "In the future, then, temperature should rise and rainfall increase. Perhaps a better time is coming — in 10,000 years!"