HH Lamb was one of the leading climate scientists at the time and founded the Climatic Research Unit at the UEA. In 1973 he wrote an article, “Is The Earth’s Climate Changing?”, for the UNESCO magazine, “The Courier”. It was a special edition devoted to climate issues and in it, HH Lamb covered a number of issues.
Early 20th Century Warming
- Computations in the United States from surface air temperature observations all over the world show that from the 1880s to some time after 1940 the Earth’s climate was becoming generally warmer. The global warming over those years amounted to about half a degree Centigrade, but in the Arctic it was much stronger and amounted to several degrees between 1920 and 1940.
- The ice on the Arctic seas decreased in extent by about 10 per cent and decreased in general thickness by about one third. Glaciers in all parts of the world were receding, opening up new pastures and land for cultivation.
- The greater warmth increased the length of the growing season by two to three weeks in England. The wild flora and forests, the cultivation of various crops, and the ranges of seasonal migration of birds and fish, all spread to new regions under the increasingly genial conditions.
- Moreover, the longest temperature records available in various northern countries from the early eighteenth century (in England from the late seventeenth century) showed that the previous warming had a very long history, traceable from the beginning of the record through various shorter-term ups and downs. This meant that the warming began before the industrial revolution and could not be altogether attributable to the effects of human activity
- For the past 25 to 30 years the Earth has been getting progressively cooler again. Around 1960 the cooling was particularly sharp. And there is by now widespread evidence of a corresponding reverse in the ranges of birds and fish and the success of crops and forest trees near the poleward and altitudinal limits.
- The decline of prevailing temperatures since about 1945 appears to be the longest-continued downward trend since temperature records began. [This period of cooling lasted about 30 years, about 5 years longer than the recent period of warming].
It is perhaps here that things become most interesting. According to Lamb, among the effects of the changes of climate in recent years, which have given cause for concern are:-
- a renewed increase (especially since 1961) of the Arctic sea ice, which has created difficulties on the northern sea routes in Soviet and Canadian Arctic waters and has produced some bad seasons on the coasts of Iceland and Greenland.
- a substantial rise, also since 1961, in the levels of the great lakes in eastern equatorial Africa and, more recently, of the Great Lakes of North America.
- some 200-year extremes of temperature in individual cold winters in various parts of the northern hemisphere (and probably also in the warmth of summer in 1972 in northern European U.S.S.R. and Finland).
- The most serious effects, however, have probably been the long-continued droughts and deficient rainfalls in various parts of the world associated with shifts of the world’s anticyclone belts.
- The subtropical anticyclones associated with the desert belt were displaced somewhat towards the equator, and the equatorial rainbelt seems to have been restricted in the range of its seasonal migrations. In consequence, rainfall increased in Africa close to the equator, causing the lakes to rise, while drought began to afflict places nearer the fringe of the desert belt, no longer reliably visited in summer by "equatorial" rains.
- Rainfall at eight places in northern India, the Sudan and at 16 to 20°N in west Africa averaged 45 per cent less in the years 1968-72 than in the 1950′s. In all these areas people have been driven from their homes by the continued failure of the rains, and in the Cape Verde Islands at the same latitude in the Atlantic an emergency was declared in 1972 because of the last five years of drought.
- There are indications that corresponding shifts have taken place in the anticyclone and cyclone belts of the southern hemisphere and that the droughts affecting Zambia, Rhodesia and parts of the Transvaal in recent years are essentially part of the same phenomenon. [An indication that Southern Hemisphere temperatures were also falling].
- At the same time, the shifting positions from month to month, and from one year to the next, occupied by the main anticyclone centres in this belt have introduced an abnormal variability of temperature and precipitation. A similar development may explain the sequence of droughts and floods in different parts of Australia in 1972-3.
In another article in this issue of The Courier, Jean Dresch, Professor of Geography at the University of Paris and a “leading authority” on the world’s arid zones, writes in more detail about the African drought that Lamb touched on.
- Famine threatens millions of villagers and herdsmen with their decimated flocks, today forced into an unprecedented migration in search of food and water, in all the West African countries to the south of the Sahara, from Mauritania to the Sudan. Its cause is drought, a prolonged decline in rainfall that has been recorded as far as central Asia, throughout the periphery of the arid zone, extending from the tropical desert of the Sahara to the continental deserts of temperate Eurasia.
- A sequence of dry years is remembered in 1910-1914, when they caused a real famine. 1941 and 1942 were no better; and dry years have been succeeding one another since 1968, whereas the decade 1951-1960 was wetter. But there is no cyclical rhythm from which to predict disasters.
Jerome Namias, “one of America’s leading weather scientists”, comments in another article, “Long Range Forecasting of Drought and Floods” :-
- We are all aware of the ravages of natural events of the recent past, the devastating Russian drought of 1972; current drought in sub-Saharan countries, especially Mali, Mauritania and the Upper Volta, which seems to have persisted and become aggravated in the last few years; the occasional seasonal droughts in parts of India and Australia and the "Seca" or" drought which occurs in some years in northeast Brazil.
- On the wet side,we have the eastern U.S.A. floods in June, 1972, associated, in part, with hurricane Agnes the most costly storm in U.S. history, and we remember the 1966 tragic flood of Florence. These are but a sample of spectacular events from the climatological record.
- From time immemorial there have been occasions when nature "goes on a rampage" and makes it appear that the climate is changing. Why does nature do this? Unfortunately man does not yet fully understand the causes of these events, and therefore he is unable to predict them reliably. [He obviously did not know about the all powerful influence of a minor trace gas].
Were they worried about what the future would bring? They might not have talked in the apocalyptic language of Time, but there was certainly concern. I will leave the final comment to HH Lamb:-
All these events have raised an anxious demand for ultra-long-range forecasting of climate, which calls for intensified effort towards understanding of the atmosphere (and its interactions with the ocean) and for further reconstruction of the facts of the past climatic record.The full edition of The Courier is here.
