What follows is a list of over 285 papers published during the 1960s, 70s and 80s showing there was a near consensus of an imminent global cooling – a fact that some activist scientists falsely dispute. They should have been far more careful in their review of the literature.
Cooling Since 1940, Forecasts for Continued Cooling/Ice Age (156 papers)
1. Kukla, 1972
Climatic changes result from variables in planetary orbits which modulate solar energy emission and change seasonal and latitudinal distribution of heat received by the Earth. Small insolation changes are multiplied by the albedo effect of the winter snow fields of the Northern Hemisphere, by ocean-atmosphere feedbacks, and, probably, by the stratospheric ozone layer. The role of volcanic explosions and other aperiodic phenomena is secondary. The immediate climate response to insolation trends permits astronomic dating of Pleistocene events. A new glacial insolation regime, expected to last 8000 years, began just recently. Mean global temperatures may eventually drop about 1oC in the next hundred years. A refinement of the Milankovitch theory in terms of the lunar orbit and more data on solar periodicities are needed for reliable long range predictions.
Has man, through increasing emissions of particulates, changed the climate?
It is estimated that man now contributes 13.6% of the 3.5 x 109 tons of primary and secondary particulates presently emitted to the atmosphere annually. … [W]hile an anthropogenic upward trend in airborne particulates existed in the past, it was halted and may even have been reversed over the past few decades.
The 1968 AAAS Symposium on Global Effects of Environmental Pollution initiated a flood of papers supporting monotonically if not exponentially increasing pollution. The particulate increases were usually cited as at least contributing to the post 1940 cooling and possibly capable of bringing on another ice age.
[F]or 50 or so years the world has been warmer than at any time in the last 300 years; in the 1940’s warmer than at any time during the last 1000 years. Since 1945 there has been a cooling trend and we are now nearly back down to the averages of the early 19th century. None of the calculations of which I am aware found that the man augmented CO2 could have contributed more than a small fraction of the warming up to 1940. Whatever the cause of the warming the post 1940 cooling appears to be primarily a return to normal.
Of the climatic problems raised the CO2 one is best understood. There is essentially universal agreement that atmospheric CO2 is increasing, increasing as a result of the consumption of fossil fuels and that this should enhance the “greenhouse” effect leading to a warming of the planetary surface. The strongest support for the upward trend in airborne particulates derives from the failure of observational data to support our understanding of the CO2 effect. Yet no one ever hears the argument that man might consider a deliberate increase in particulates to counter the CO2 effect or alternatively that the CO2 effect is just what is needed to prevent or delay the onset of the next glacial advance which is now imminent according to students of this problem. The failure of these latter arguments to receive equal time indicates a decided bias in our systems for informational exchange and it is the possibility that such a decided bias can exist that I consider to be the greatest threat to our future.
Aside from such long-term changes, there is also evidence which indicates climate changes occurring in contemporary history. Mitchell (1971) among others, claims that during the last century a systematic fluctuation of global climate is revealed by meteorological data. He states that between 1880 and 1940 a net warming of about 0.6°C occurred, and from 1940 to the present our globe experienced a net cooling of 0.3°C.
The effect of increasing global concentrations of CO2 is to increase the average global surface temperature. … As for increasing global concentrations of particulate matter, the opposite is true. Due to the backscattering characteristics of the particles an increase in the albedo occurs which produces a decrease in average global surface temperature. … Since it had been thought that the two effects canceled one another, their use as criteria for developing standards has not been considered. However, it has since been found that the rate of temperature increase decreases with increasing CO2 and increases with increasing particulates. Therefore, global particulate loading is of foremost concern. … Sellers (1973) has developed a climate model which quantitatively relates particulate loading to surface temperature. He has shown that an increase in man-made global particulates by a factor of 4.0 will initiate an ice-age. In order that we safeguard ourselves and future generations from a self-imposed ice-age it is necessary that we effectively monitor global concentrations of particulate matter. … Their results showed that an increase by a factor of eight of global CO2 concentrations will produce an increase in surface temperature of less than 2°C, whereas increasing particulate concentration by a factor of four could decrease the mean surface temperature as much as 3.5°C. Therefore, as the global concentrations of both CO2 and particulates are increased, it is the radiative shielding effect of the particulates which plays the dominate role. … Ludwig and Morgan, 1970, predict that man’s potential to pollute will increase six-to-eight fold in the next fifty years. All of these studies point to the possibility, in the not so distant future, of man polluting himself into an ice age.
The Upward Trend in Airborne Particulates That Isn’t
Introduction: In recent years there have appeared a rash of papers claiming an upward trend in airborne particulates, which is presumed to have already reversed the alleged CO2 induced heating of the atmosphere observed between the 1880’s and 1940’s and to pose the further threat of inducing another ice age. Allusions to the trend have become so common that many authors now cite it as an accepted reality requiring neither qualification nor attribution by reference.
5. Agee, 1980
Evidence has been presented and discussed to show a cooling trend over the Northern Hemisphere since around 1940, amounting to over 0.5°C, due primarily to cooling at mid- and high latitudes. Some regions of the middle latitudes have actually warmed while others, such as the central and eastern United States, have experienced sharp cooling. A representative station for this latter region is Lafayette, Ind., which has recorded a drop of 2.2°C in its mean annual temperature from 1940 through 1978. The cooling trend for the Northern Hemisphere has been associated with an increase of both the latitudinal gradient of temperature and the lapse rate, as predicted by climate models with decreased solar input and feedback mechanisms. … Observations and interpretation of sunspot activity have been used to infer a direct thermal response of terrestrial temperature to solar variability on the time scale of the Gleissberg cycle (∼90 years, an amplitude of the 11-year cycles). Measurements at the Greenwich Observatory and the Kitt Peak National Observatory, as well as other supportive information and arguments, are presented to hypothesize a physical link between the sunspot activity and the solar parameter. On the time scale of the Gleissberg cycle when the mean annual sunspot number exceeds 50 it is proposed that global cooling may be initiated due to the decreased insolation. This is also supported by umbral-to-penumbral ratios computed and interpreted by Hoyt (1979a).
The summaries by Schneider and Dickinson (1974) and Robock (1978) show that the mean annual temperature of the Northern Hemisphere increased about 1°C from 1880 to about 1940 and then cooled about 0.5°C by around 1960. Subsequently, overall cooling has continued (as already referenced) such that the mean annual temperature of the Northern Hemisphere is now approaching values comparable to that in the 1880s. This present cooling trend has also been shown by Williams and Van Loon (1976) for the region 15°-80°N, and amounts to -0.26°C for the period 1942-72. A critical consideration, as they state, is the role (if any) played by the tropics and the Southern Hemisphere to counterbalance this cooling. Nonetheless, the evidence the seems clear that above 15°N the Northern Hemisphere is experiencing a significant climate cooling trend, and the apparent controversy over warming or cooling (or neither) should not exist. In passing, the work by Lorenz (1968, 1970, 1976, 1979) deserves further notice, namely that “climatic change” might just be the natural variations due to the complex non-linear interactions among various components of the climate system.
6. Benton, 1970
Climate is variable. In historical times, many significant fluctuations in temperature and precipitation have been identified. In the period from 1880 to 1940, the mean temperature of the earth increased about 0.6°C; from 1940 to 1970, it decreased by 0.3-0.4°C. Locally, temperature changes as large as 3-4°C per decade have been recorded, especially in sub-polar regions. … The drop in the earth’s temperature since 1940 has been paralleled by a substantial increase in natural volcanism. The effect of such volcanic activity is probably greater than the effect of manmade pollutants.
7. National Academy of Sciences, 1975
A striking feature of the instrumental record is the behavior of temperature worldwide. As shown by Mitchell (1970), the average surface air temperature in the northern hemisphere increased from the 1880’s until about 1940 and has been decreasing thereafter. Starr and Oort (1973) have reported that, during the period 1958-1963, the hemisphere’s (mass-weighted) mean temperature decreased by about 0.6 °C. In that period the polar and subtropical arid regions experienced the greatest cooling. The cause of this variation is not known, although clearly this trend cannot continue indefinitely. … The well-documented warming trend of global climate beginning in the 1880’s and continuing until the 1940’s is a continuation of the warming trend that terminated the Little Ice Age. Since the 1940’s, mean temperatures have declined and are now nearly halfway back to the 1880 levels.
There seems little doubt that the present period of unusual warmth will eventually give way to a time of colder climate, but there is no consensus with regard to either the magnitude or rapidity of the transition. The onset of this climatic decline could be several thousand years in the future,although there is a finite probability that a serious worldwide cooling could befall the earth within the next hundred years. … If the end of the interglacial is episodic in character, we are moving toward a rather sudden climatic change of unknown timing, although as each 100 years passes, we have perhaps a 5 percent greater chance of encountering its [the next glacial’s] onset.
8. Hare, 1971
It is discouraging to have to start by admitting that future changes in the atmosphere may be the result of the inherent instability of the atmospheric circulation, and not of environmental changes that we can detect, and perhaps control. If the environmental forcing does not change, moreover, its effects may be masked by free internal fluctuation of opposite sign. Much of our research into the causes of post-climatic variation is based on the assumption that they are not so masked, just as we often assume that the atmosphere is deterministic and unique in behavior when we argue for bigger computers and bigger appropriations. … Explaining past climates and predicting future climates are complementary processes. As Murray Mitchell pointed out, also at Boulder (Mitchell, 1968), we are miles away from explaining the past, whose record is so blurred that there remain open “many degrees of freedom for the construction of altogether new hypotheses.” He laid stress where I shall place it today — on the view that explaining climatic variation must rest on an adequate theory of existing climate. Until we can argue backwards and forwards in time from such a secure foundation we shall continue to be the blind led by the blind.
[M]ost recent years of hemispheric surface temperatures (Mitchell, 1970) show rises of about 0.6C over the 0-80N belt between 1880 and 1940, followed by a subsequent decline to current temperatures about 0.3C above 1880. The Southern Hemisphere seems to be in phase [with the Northern Hemisphere], but amplitudes are rather smaller. There have probably been small, corresponding changes in sea temperatures. Precisely what the fluctuations reflect is not clear, though they mean large changes in stored energy. … Recent debates have been about the relative effectiveness of dust and carbon dioxide influences … It is clear, however, that sound meteorological estimates of the troposphere and surface warming to be expected from this increase [in CO2] (e.g., Manabe and Wetherland, 1967) do not account for the observed temperatures variations. The rise between 1880 and 1940 was much greater than the computed carbon dioxide effect, and since 1940 temperatures have actually fallen as the rise in [CO2] mixing ratio accelerated.
The second hypothesis much in vogue — that the cooling is due to widespread atmospheric turbidity — derives from this fact. There have been reports of substantial increases in turbidity … [which] have greatly accelerated in recent years … There has also been an upsurge in vulcanism since 1948, after a 30-year period of quiet (Lamb, quoted by Mitchell, 1970). The unfortunate lack of systematic observations of dustiness … makes precision impossible … It seems clear that the observed turbidity increases are real, and are effective in lowering temperatures; moreover, they are due in some part to human interference. Quantitative estimates, however, are not yet really credible.
A recent flurry of papers has provided further evidence for the belief that the Earth is cooling. There now seems to be little doubt that changes over the past few years are more than a minor statistical fluctuation. … On page 45 of this issue of Nature, Wahl and Bryson compare recent sea surface temperature patterns with those of cooler regimes in the past, and conclude that over the period from 1951 to 1972 there was a decline corresponding “to a return of about one-sixth of the way to full ice age.” … The observed cooling corresponds to a re-establishment of the ‘Little Ice Age’ which persisted for several hundred years up to the end of the nineteenth century; it may be that all that has happened since 1950 is that the unusually mild spell of the first part of this century has ended.
10. NOAA, 1974
In the Sahelian zone of Africa south of the Sahara, the countries of Chad, The Gambia, Mali, Mauritania, Niger, Senegal, and Upper Volta are enduring a drought that in some areas has been going on for more than six years now, following some 40 previous years of abundant monsoon rainfall. And the drought is spreading—eastward into Ehtiopia and southward into Dahomey, Egypt, Guinea, Kenya, Nigeria, Somalia, Tanzania, and Zaire. … Many climatologists have associated this drought and other recent weather anomalies with a global cooling trend and changes in atmospheric circulation which, if prolonged, pose serious threats to major food-producing regions of the world. … Annual average temperatures over the Northern Hemisphere increased rather dramatically from about 1890 through 1940, but have been falling ever since. The total change has averaged about one-half degree Centigrade, with the greatest cooling in higher latitudes. A drop of only one or two degrees Centigrade in the annual average temperature at higher latitudes can shorten the growing season so that some crops have to be abandoned. … [T]he average growing season in England is already two weeks shorter than it was before 1950. Since the late 1950’s, Iceland’s hay crop yield has dropped about 25 percent, while pack ice in waters around Iceland and Greenland ports is becoming the hazard to navigation it was during the 17th and 18th centuries. … Some climatologists think that if the current cooling trend continues, drought will occur more frequently in India—indeed, through much of Asia, the world’s hungriest continent. … Some climatologists think that the present cooling trend may be the start of a slide into another period of major glaciation, popularly called an “ice age.”
“Potential Implications of Trends in World Population, Food Production, and Climate”
According to Dr. Hubert Lamb–an outstanding British climatologist–22 out of 27 forecasting methods he examined predicted a cooling trend through the remainder of this century. A change of 2°-3° F. in average temperature would have an enormous impact. [pg. 28, bottom footnote]
A number of meteorological experts are thinking in terms of a return to a climate like that of the 19th century. This would mean that within a relatively few years (probably less than two decades, assuming the cooling trend began in the 1960’s) there would be brought belts of excess and deficit rainfall in the middle-latitudes; more frequent failure of the monsoons that dominate the Indian sub-continent, south China and western Africa; shorter growing seasons for Canada, northern Russia and north China. Europe could expect to be cooler and wetter. … [I]n periods when climate change [cooling] is underway, violent weather — unseasonal frosts, warm spells, large storms, floods, etc.–is thought to be more common.
Why has the earth cooled? There are three main factors involved affecting how much sunlight reaches the earth and how much is re-radiated into space: volcanic dust, man-made dust, and carbon dioxide . The transparency of the atmosphere to incoming sunlight and heat is affected by dust. The main variable sources of dust are volcanic activity and man-made pollution. In the early part of this century, volcanic activity decreased markedly and this increased transparency; temperatures rose. Bryson estimates that transparency was little affected by man’s activities until about 1930 but that since then, man-caused dust has increased rapidly. And, since the mid-1950’s volcanic activity has again become important.
12. Flohn, 1974
Since about 1945 [to 1974], global cooling, on a scale of -0.01°C/yr [-0.3°C total], has reversed the warming trend of the first decades of our century. The bulk of these changes is probably not man-made, but of natural origin. … A large majority of the participants of the symposium concluded that the present warm epoch has reached its final phase, and that—disregarding possible man-made variations are comparable in scale with the effects–the natural end of this interglacial epoch is “undoubtedly near.”
The conclusions of the NDU study might have been predicted from a knowledge of the prevailing ‘spirit of the times’ (i.e., the prevailing mood in the science community) when the first part was conducted. This was an interesting time in recent history of climate studies. One could effectively argue that in the early 1970s the prevailing view was that the earth was moving toward a new ice age. Many articles appeared in the scientific literature as well as in the popular press speculating about the impact on agriculture of a 1-2°C cooling. By the late 1970s that prevailing view had seemingly shifted 180 degrees to the belief that the earth’s atmosphere was being warmed as a result of an increasing CO2 loading of the atmosphere
The causes of global climate change remain in dispute. Existing theories of climate, atmospheric models, and actuarial experience are inadequate to meet the needs of policymakers for information about future climate. In the long run, research may lead to reliable forecasts of climate. For the present, however, policymakers have no recourse but to heed expert judgments – subjective and contradictory though they may be – about future world climate and its effects on agriculture and other sectors of the economy. Informed, expert judgments on the likelihood of change, or the odds for a repetition of some event, are useful to the decisionmaker weighing the costs, benefits, and risks of alternative policies (NDU, 1978. p. ix).
14. Curry, 1969
At least four major periods of increased mean snowfall and cooler, cloudier summers during the last 10,000 years resulted in four periods of multiple glacial advance in the Sierra Nevada. These occurred  between 6000 and 7000 years ago,  between 2000 and 2600 years ago,  around 1000 years ago, and  between 650 years ago and the present. The latest major period of net accumulation and advance in all cirques that are presently occupied by residual glaciers occurred between 1880 and 1908 with a peak from 1895 to 1897.
[By including the last 650 years to the present, the authors strongly imply that the present 1960s-era climate had not sufficiently warmed enough to be distinguished from the post-1400 AD Little Ice Age.]
Here, the ages of Little Ice Age moraines suggest fluctuating glacier expansion between ad 1500 and the early 20th century. Much of the 20th century has experienced glacier recession, but probably it would be premature to declare the Little Ice Age over. The complex moraine systems of the older expansion interval lie immediately downvalley from Little Ice Age moraines, suggesting that the two expansion intervals represent similar events in the Holocene, and hence that the Little Ice Age is not unique.
Viewed as a whole, therefore, the Holocene experienced alternating intervals of glacier expansion and contraction that probably were superimposed on the broad climatic trends recognized in pollen profiles and deep-sea cores. Expansion intervals lasted up to 900 yr and contraction intervals up to 1750 yr. Dates of glacial maxima indicate that the major Holocene intervals of expansion peaked at about 200–330, 2800, and 5300 calendar yr BP, suggesting a recurrence of major glacier activity about each 2500 yr. … Moreover, comparison of presumed analogues such as the Little Ice Age and the Younger Dryas, or the Alleröd and the Roman Empire-Middle Ages warm interval, show marked similarities. These results suggest that a recurring pattern of minor climatic variations, with a dominant overprint of cold intervals peaking about each 2500 yr, was superimposed on long-term Holocene and Late-Wisconsin climatic trends. Should this pattern continue to repeat itself, the Little Ice Age will be succeeded within the next few centuries by a long interval of milder climates similar to those of the Roman Empire and Middle Ages. … The most prominent explanation of short-term C14 variations involves modulation of the galactic cosmic-ray flux by varying solar corpuscular activity. If this explanation proves valid and if the solar constant can be shown to vary with corpuscular output, it would suggest that Holocene glacier and climatic fluctuations, because of their close correlation with short-term C14 variations, were caused by varying solar activity.
[The use of future tense in the statement that the Little Ice Age “will be succeeded within the next few centuries by a long interval of milder climates” similar to the Medieval and Roman Warm Periods strongly implies that the authors did not agree that modern (1970s) climate had sufficiently emerged from the Little Ice Age to yet qualify as a warm interval , and that it might be a “few centuries” before this warm period might commence.]
Sagan et al. have suggested that the cumulative impact of anthropogenic albedo changes may have contributed to global climate changes in the past and that its effect may be continuing. Using a statistical dynamic climate model (SDM) with more realistic surface albedo changes than previously used, we have computed the combined impact of desertification of the Sahara and deforestation of the tropical rain forest. While the model computed a surface cooling of 0.6 K for the Northern Hemisphere, the global mean of ~0.2 K was substantially less than the 1 K [of anthropogenic global cooling] suggested by Sagan et al. We infer that man’s cumulative impact on planetary surface albedo over the past few thousand years has had a small and probably undetectable effect on global climate.
18. Brinkmann, 1979
Introduction: Concern about the impact of the recent downward trend in the average surface temperature for the ‘Northern Hemisphere’ (Reitan, 1974; Angell and Korshover, 1975) on the world food supply has led to an increasing interest in possible changes in the length of the growing season (NRC, 1976; NRC, 1977). There is also concern over possible increases in weather variability and its impact on food supply (Thompson, 1975). Increased variability has been proposed to be linked to hemispheric cooling and associated amplification of the circumpolar wave pattern which would cause greater extremes in weather (Bryson, 1975; Lamb, 1975). Most studies of climatic variability have been concerned with variance on the monthly, season, and annual scale (van Loon and Williams, 1978; Ratcliffe et al., 1978). But it is also possible that the variability of daily temperatures is changing, which could affect the length of the growing season. An increase in the magnitude and/or frequency of very low daily minimum temperatures, for instance, could result in a later onset of the ‘freeze free’ season and an earlier end.
19. Wright, 1972
The Holocene has already run a course of at least 10,000 yr. If it is like earlier interglacials, it will end soon, giving way to gradually developing cold conditions, which may not lead to glacial maxima for tens of thousands of years.
“A Study of Climatological Research as it Pertains to Intelligence Problems”
The western world’s leading climatologists have confirmed recent reports of a detrimental global climate change. The stability of most nations is based upon a dependable source of food, but this stability will not be possible under the new climatic era. A forecast by the University of Wisconsin projects that the earth’s climate is returning to that of the neo-boreal era (1600-1850) – an era of drought, famine, and political unrest in the western world [the Little Ice Age]. … The world is returning to the type of climate which has existed over the last 400 years. That is, the abnormal climate of agricultural-optimum is being replaced by a normal climate of the neo-boreal era.
The climate change began in 1960, but no one including the climatologists recognized it. Crop failures in the Soviet Union and India during the first part of the sixties were attributed to the natural fluctuation of the weather. India was supported by massive U.S. grain shipments that fed over 100 million people. To eat, the Soviets slaughtered their livestock, and Premier Nikita Khrushchev was quietly deposed.
During the remainder of the 1960s, the climate change remained hidden in those back washes of the world where death through starvation and disease were already a common occurrence. The six West African countries south of the Sahara…became the first victims of the climatic change. The failure of the African monsoon beginning in 1968 has driven those countries to the edge of economic and political ruin. They are now effectively wards of the United Nations and depend on the United States for a majority of their food supply.
Later, in the 1970s, one nation after another experienced the impact of the climatic change. The headlines from around the world told a story not fully understood or one we don’t want to face, such as:
* Burma (March 1973) – little rice export due to drought
* North Korea (March 1973) – record high grain import reflected poor 1972 harvest
* Costa Rica and Honduras (1973) – worst drought in 50 years
* United States (April 1973) -“flood of the century along the Great Lakes”
* Japan (1973) – cold spell seriously damaged crops
* Pakistan (March 1973) – Islam planned import of U.S. grain to off-set crop failure due to drought
*North Vietnam (September 1973) – important crop damaged by heavy rains
* Manila (March 1974) – millions in Asia face critical rice shortage
* Ecuador (April 1974) – shortage of rice reaching crisis proportion; political repercussions could threaten its stability
* USSR (June 1974) – poor weather threatens to reduce grain yields in the USSR
* China (June 1974) – droughts and floods
* India (June 1974) – monsoons late
* United States (July 1974) – heavy rain and droughts cause record loss to potential bumper crop
Because of the global cooling trend, the lower edge of the circumpolar vortex has in recent years stayed farther south during the summer, in the position shown by the smaller band near the equator. It has kept the high pressure zones farther south too, blocking the monsoons out of regions where they are vital to the survival of hundreds of millions of people. At the same time, the vortex’s semistationary wave patterns have altered, affecting rainfall patterns in temperate regions and making the climate more variable. The deeper wave over the U.S., for example, is believed responsible for recent cold winters in the West and mild ones in the East. The West has been subjected to north winds; the East, the return flow. Although some evidence exists that the cooling trend has affected wind patterns in the Southern Hemisphere as well, weather statistics are scanty.
Since the late 1960s, a number of foreboding climatic predictions has appeared in various climatic, meteorological, and geological periodicals, consistently following one of two themes.
* A global climatic change was underway
* This climatic change would create worldwide agriculture failures in the 1970s.
Early in the 1970s, a series of adverse climatic anomalies occurred:
* The world’s snow and ice cover had increased by at least 10 to 15 percent.
* In the eastern Canadian area of the Arctic Greenland, below normal temperatures were recorded for 19 consecutive months. Nothing like this had happened in the last 100 years.
* The Moscow region suffered its worst drought in three to five hundred years.
* Drought occurred in Central America, the sub-Sahara, South Asia, China, and Australia.
* Massive floods took place in the midwestern United States
Within a single year, adversity had visited almost every nation on the globe. … With global climatic-induced agricultural failures of the early 1970s, the stability of many governments has been seriously threatened. Many governments have gone to great lengths to hide their agricultural predicaments from other countries as well as from their own people. It has become increasingly imperative to determine whether 1972 was an isolated even or – as the climatologists predicted – a major shift in the world’s climate.
21. Robock, 1978
Instrumental surface temperature records have been compiled for large portions of the globe for about the past 100 years (Mitchell, 1961; Budyko, 1969). They show that the Northern Hemisphere annual mean temperature has risen about 1°C from 1880 to about 1940 and has fallen about 0.5 °C since then (Figs. 1-3). Various attempts to simulate this temperature record (Schneider and Mass, 1975; Pollack et at., 1976; Bryson and Dittberner, 1976) have all focused on external causes, such as volcanic dust, solar constant variations and anthropogenic effects. It is possible, however, that even in the absence of any external forcing a unique climate may not exist. Climate change may be a natural internal feature of the land-oceanic-atmosphere (climate) system.
Three runs were made testing anthropogenic effects of CO2, aerosols and heat. … One could sum the anthropogenic effects for each region, which would show almost no effect in the NH and warming in the SH. Drawing conclusions from this exercise would not be meaningful, however, due to our lack of understanding of the aerosol effect. All the effects almost double every 20 years. They are not of sufficient magnitude to have much effect on the observational records, which end about 1960, but may have a measurable effect in the near future. The relative magnitudes of the effects may change in the future due to changing human pollution policies. Restrictions on particulate pollution and anticipated measures against sulfate aerosols will lessen the effects of industrial aerosols. Increased dependence on nuclear energy would increase the ratio of heat to CO2 effect, while an increased dependence on coal would not. … Because the magnitudes of the effects are small, and may cancel, it cannot be concluded that these high correlations show that man has produced climate change.
22. Magill, 1980
Recent anomaloous weather conditions of the 1970s have revealed the possibility that significant aberrations in global climate have and are occurring with serious consequences. The 1970s have seen a generally overall greater variability and instability of global weather. Regions in Asia, Central America, and Africa have witnessed a higher frequency of monsoon failure which has led to a prevalence of severe drought conditions and an extension of desert boundaries. Whereas in other parts of the globe, severe flooding has been recorded. … Records of past climates have indicated that a greater variability of climate is generally synonymous with a major cooling trend in temperatures.
[A] general consensus that a major upheaval in climate is taking place. …There is no way of determining, however, whether or not the world is entering into another major ice age or if the present cooling of temperatures is simply a pause in the warming trend that began in the mid1800s. At present, insufficient knowledge is available on the delicate balance among the various interacting factors controlling climate to determine precisely the future course of climate.
The trend of world temperature in this century appears to be directly related to the trends of atmospheric carbon dioxide content and atmospheric turbidity (dustiness). Both are believed by various scholars to be related to human activities. Since 1940, the effect of the rapid rise of atmospheric turbidity appears to have exceeded the effect of rising carbon dioxide, resulting in a rapid downward trend of temperature. There is no indication that these trends will be reversed, and there is some reason to believe that man-made pollution will have an increased effect in the future.
An appreciable number of nonurban stations in the United States and Canada have been identified with statistically significant (at the 90% level) decreasing trends in the monthly mean diurnal temperature range between 1941–80. The percentage of stations in the network showing the decrease is higher than expected due to chance throughout the year, with a maximum reached during late summer and early autumn and a minimum in December. Monte Carlo tests indicate that during five months the field significance of the decreasing range is above the 99% level, and in 12 months above the 95% level. There is a negligible probability that such a result is due to chance. … The physical mechanism responsible for the observed decrease in the diurnal range is not known. Possible explanations include greenhouse effects such as changes in cloudiness, aerosol loading, atmospheric water vapor content, or carbon dioxide.
Introduction: As described m ore fully in the accompanying state-o f-the-art report on the Detecting the Climatic Effects of Increasing Carbon Dioxide (see Chapter 4 by Wigley et al. 1985), there is no clear indication of a monotonic warming over this period [1880-1980], as would be anticipated from the observed build up of CO2 in the atmosphere. Instead, these data sets indicate a complex picture including interannual variability and, perhaps, some systematic trends. Indeed, the global temperatures seem to have increased from 1885- 1935, and the extent of Arctic sea ice decreased from 1925-1945. This was followed, however, by a leveling off and then a subsequent decrease in temperature. Although it is possible that the data sets are incomplete, these surface air temperatures do not appear to display the monotonic increase in global mean temperatures predicted by CO2-driven climate models. This does not necessarily mean an absence of an effect thus far, because the superposition of climatic variability from other ay obscure the signal. Among o th er things, therefore, transient climate models are needed to address whether historical records are consistent with predictions of past warming from increasing CO2 concentrations, as well as where and when a climate change is likely to be observed in the future.
26. Schneider, 1974
Introduction: In the last century it is possible to document an increase of about 0.6°C in the mean global temperature between 1880 and 1940 and a subsequent fall of temperature by about 0.3°C since 1940. In the polar regions north of 70° latitude the decrease in temperature in the past decade alone has been about 1°C, several times larger than the global average decrease (see Fig. 3.8 in the SMIC Report). Up till now, past climatic changes (except possibly those of the last few decades [of cooling temperatures]) could hardly have been caused by man’s activities. However, we have recently realized that man has altered the face of the earth and the composition of the atmosphere on such a large scale that his influence can no longer be ignored relative to nature’s. … Two of the most publicized means by which it is thought man could influence climate are related to the dumping of CO2 and ‘dust’ particles (or gases such as SO2 which are subsequently converted to atmospheric particles) into the atmosphere, from activities that are usually associated with the burning of fossil fuels. … Some scientists already feel that particles might be responsible for the recently observed decrease in the earth’s temperature
The climatic warming trend since the 1880s, which seems to have been global in extent and was manifested by an upward trend in mean annual (and particularly mean winter) temperatures, seems to have given way since the 1940s to a cooling trend, which is most marked in higher latitudes.
28. Collis, 1975
It is not clear how such favorable and relatively consistent conditions are related to the higher temperatures in this century or the peaking of temperatures around 1940. The reversal of this warming trend, however, could mark the beginning of a new ice age as some climatologists have indicated. It should be noted, though, that even if we are in fact heading for another ice age, many years or decades will elapse before this will become apparent
29. Haber, 1974
A meteorologist and Director of the Institute for Environmental Studies at the University of Wisconsin, Dr. Bryson believes that the Earth is moving toward an inevitable climate change; the consequences, he says, are already being felt – tragically – in the drought-plagued belt of West Africa called the Sahel. The global climate will become cooler, Bryson predicts, the pattern of rainfall will change, and a southward movement of the subtropical deserts will take place. Since rainfall and climate affect crop growth, since crop growth affects food supply, and since food supply affects life itself, Bryson’s prediction may be of paramount importance to mankind. The drought that has gripped West Africa since the late 1960s is just one reminder that climate cannot be taken for granted. There is little “green” on present-day Greenland, but sedimentary remains, deep below the thick slab of ice that blankets four-fifths of the island, reveal prehistoric existence of oak and chestnut trees and other forms of verdure. In northern Europe, deposits formed 40,000 years ago include fossils of palms and other plants associated with warmer climes.
30. Ghil, 1975
We turn now to the question of which features of atmospheric phenomena are “most important.” Certainly temperature is one of them …. Also humidity, wind direction and intensity, cloud amount and precipitation, all play a major role in determining what is perceived as weather and hence should be time-averaged (and, possibly, space-averaged) into climate. … Some attribute the assumed decreases in solar radiation to changes in the parameters of the motions of our planet (Milankovitch, 1969), others to airborne volcanic dust due to an increase in volcanic activity (Fuchs and Patterson, 1947), and so on. There has also been a concern about a possible climatic catastrophe [global cooling] being imminent because of the increase in the quantity of industrial pollutants in the atmosphere (Rasool and Schneider, 1971).
[CO2 not mentioned as a “most important” feature of atmospheric climate determinants.]
31. Wahl, 1968
A comparison of climatic data for the eastern United States from the 1830’s and 1840’s with the currently valid climatic normals indicates a distinctly cooler and, in some areas, wetter climate in the first half of the last century. The recently appearing trend to cooler conditions noticed here and elsewhere could be indicative of a return to the climatic character of those earlier years [1830s, 1840s].
This penultimate climatic episode, called the “Neoboreal” by Baerreis and Bryson (1965) and also frequently referred to as the “Little Ice Age” (Brooks, 1951) apparently started during the middle of the 16th century at a time of glacial advances both in Europe and North America. It continued as a distinctly cooler, and, in some regions, wetter period well into the 19th century. Following it was a warming trend that between 1880 and 1940 to 1950 became quite pronounced in very many regions of the Northern Hemisphere. During the last two decades there appears to be some evidence that this warming trend of the last 100 yr. has changed over recently to a distinct new deterioration of the climate, leading to conditions that in the 1960’s appear to approach those which were generally found around the turn of the century or even earlier, i.e. a return to the climatic character of the 19th century … A downward trend of the mean temperature, especially in early fall, will tend to increase the likelihood of early frosts (such as Wisconsin experienced in 1965 with some killing frost in lowlands on July 6) and thus may require changes in agricultural practices. One should not forget that an average decrease in mean monthly averages of about 4° is equivalent to a displacement of the isotherms by about 4° latitude or 250 to 300 mi., or to reaching a certain temperature threshold about 10 days earlier in fall.
32. Fairbridge, 1972
Within any given cycle there is an Interglacial, Anaglacial, Pleniglacial and Kataglacial phase, characteristics of which are repeated on a small scale in minor cycles. Their timing is variable in a latitudinal sense, apparently steered by radiation changes that first affect the tropics. Interglacials are defined in their classical stratotype areas of NW Europe, by sedimentary sequences characterized by the pollen of deciduous forests, pointing to climates at least as warm as those of the present time. The present cycle began ca. 10,000 YBP, with the start of the Holocene epoch, and the contemporary warm phase is seen as a typical interglacial stage. Such warm peaks characteristically last about 10,000 yr. Symptoms of the expected ensuing glaciation range from a global fall in temperature since mid Holocene, to tropical desiccation (growth of deserts) and high latitude retreat of tree lines.
33. Eichenlaub, 1970
Evidence suggests that lake effect snowfall has significantly increased during the past several decades, particularly in Southern Michigan and Northern Indiana. While the observed changes cannot be definitively ascribed to any single factor, it seems likely that a general cooling of winter temperatures may be partially responsible for this climatic change. [M]any of the snowfall time-series curves for the lake stations show downward trends during the 1920’s and 1930’s, at the height of the recent warm period, and the more recent snowfall increase has coincided with a general world-wide cooling which has occurred in the last several decades [1940s-1970s]. Recent evidence derived from [isotope] analysis of ice core samples on the Greenland ice cap indicates a continuance of this cooling trend for another 20 or 30 years [through the 1990s].
34. Budyko, 1969
To answer the question of in what way the climate will change in the future, it is necessary to establish the causes of Quaternary glaciations initiation and to determine the direction of their development. Numerous studies on this problem contain various and often contradictory hypotheses on the causes of glaciations. … [A] rise in temperature that began at the end of the last century stopped in about 1940, and a fall in temperature started. The temperature in the northern hemisphere that increased in the warming period by about 0.6oC then decreased by the middle of the fifties by 0.2oC. A compartively short-period rise in temperature with smaller amplitude was also observed in the last years of the [19th] century. … Thus, it seems probable that the present changes in the Earth’s temperature are determined mainly by the atmospheric transparency variations that depend on the level of volcanic activity. … If with the decrease in radiation by 1% the mean temperature of the Earth drops by 5o, then with the decrease in radiation by 1.5% such a drop reaches 9o. Simultaneously with the above temperature drop the glaciation displacement 10-18o to the south takes place, i.e. the distances approximately corresponding to the expansion of the quarternary glaciations. … Thus, the present thermal regime and glaciations of the Earth prove to be characterized by high instability. Comparatively small changes of radiation — only by 1.0 – 1.5% — are sufficient for the development of ice cover on the land and oceans that reaches temperate latitudes. It should be noted that such changes in radiation are only several times as great as its variations observed due to the changeability of volcanic activity in the last century. Taking into consideration that according to the data of geological investigations the level of volcanic activity for long periods of time in the past changed by a factor of several times (see Ronov, 1959), one can believe that the influence of long-period variations of volcanic activity is a probable factor of glaciation development.
35. Hughs, 1970
Convection in the Antarctic Ice Sheet Leading to a Surge of the Ice Sheet and Possibly to a New Ice Age
[A] surge of the ice sheet appears likely.
36. Fletcher, 1970
[F]rom about 1890 to 1940 the general but irregular trend was toward growing strength of the global atmospheric circulation, northward displacement of the polar fronts in both the atmosphere and the ocean, northward displacement of ice boundaries in both the arctic and antarctic, weaker development of anticylones over the continents and more northward cyclone paths. These dynamic changes were reflected by a dramatic warming of the arctic and of the North Atlantic, and aridity in the south central parts of North America and Eurasia. Conversely, recent decades have exhibited opposite trends: weakening planetary circulation, southward shifts of ice boundaries and cyclone paths and sharp cooling and different rainfall patterns over continents. … Less than 20,000 years ago the Wisconsin ice sheet covered North America from the Atlantic to the Pacific and was up to two miles thick. Most of this vast ice mass melted during the only a few thousand years, raising the level of the world ocean by several hundred feet. This warming culminated in a “climatic optimum” from about 4000-2000 B.C., during which world temperatures were four to five degrees warmer than they are now and rainfall patterns were very different. … [T]he secondary “climatic optimum” around 1000 A.D. [was] a period characterized by a relatively dry, warm and storn-free North Atlantic which permitted the great viking colonization of Greenland and Newfoundland. The decline, from about 1300 A.D., with one partial recovery from about 1400 to 1550, continued to about 1750, culminating in the “little ice age” of 1650-1840. During the cooling period, North Atlantic ice boundaries advanced and the Viking colonies were extinguished. The warming since the cooling climax of the 1700s continued irregularly up to the 1940s, when renewed cooling seems to have set in.
37. Thompson, 1975
A cooling trend in the world’s climate would have serious effects in the monsoon belts depending on whether or not the recent changes in snow and ice cover in the polar regions were responsible for the droughts in Africa and the failure of the monsoons over South Asia. The cooling and shrinking of the atmosphere at the higher latitudes is believed to have brought the subtropical anticyclones nearer to the tropical rainbelt and have caused a shifting of the monsoon belt. The regions that would be most severely affected by a continuation of the cooling trend to the year 2000 would be the higher latitudes (above 50 degrees) where spring wheat is grown and the warm band below 30 degrees latitude where rice is the principal grain crop. Weather variability is a much more important consideration in grain production than a cooling trend. Our highest yields are made when weather is near normal or slightly cooler than normal. It is when weather variables deviate greatly from normal that yields are lowest. Even if the weather does trend toward the coolness of a century ago yields will not be reduced significantly unless the weather becomes more variable.
38. Fletcher, 1968
Since the “little ice age” of 1650-1840, which climaxed the cooling trend from about 1300, a new warming trend predominated which seems to have reached a climax in the 1920’s, followed by cooling since about 1940, at first irregularly but then sharply since about 1960. The periods of general warming were accompanied by increasing vigor of the westerly zonal circulation in both hemispheres, bringing a more maritime climate to the continents, more northerly cyclone tracks and a pronounced warming of the Arctic. (From 1890 to 1940 the mean thickness of Arctic pack ice decreased by more than 1/3rd (Ahlmann, 1945). Since about 1940 the reverse pattern has occurred, with weakened zonal circulation, greater development of blocking anticyclones over continents in winter, more variable and southerly cyclone paths, and a colder Arctic. … No one has been able to explain why such climatic variations occur. They seem to be associated with variations in the vigor of the whole global atmospheric circulation, but why the global system varies is still a mystery. … [T]he sharp global cooling of the past decade indicates that other factors are more influential than increasing CO2. For example, Moller (1953) estimates that a 10% change in CO2 can be compensated by a 3% change in water vapor or a 1% change in mean cloudiness. Moreover, the oceans have an enormous capacity to absorb CO2, which also varies with temperature; that is, colder oceans can store more CO2. Thus, warming oceans could be a primary cause of increasing CO2 in the atmosphere. In summary, it appears that, other factors being constant, CO2 from human activity could cause important changes of global climate during the next few decades. But , of course, other factors are not constant, and in recent years have apparently been more influential than the CO2 increase.
39. Schneider, 1978
In the short term (left) the temperature has risen by about 1/2 degree Celsius since the 1880s, and from the middle 1940s to the middle 1960s it dropped about 1/4 degree. What’s wrong with this picture is that there should be large error bars on it, because there are still vast regions of oceans not covered by thermometers. But the main point is that the range of variation is only on the order of 1/2 degree, and that’s probably been significant enough to cause important local changes.
Departures of mean annual precipitation and temperature for the decade 1961–1970 from the 1931–1960 averages are illustrated on maps of the tropical and subtropical portions of the American continents. Certain features of midlatitude climatic anomalies appear to be associated with concurrent anomalies in the tropics. There is an apparent southward shift of circulation features in this longitudinal sector of both hemispheres. A review of selected literature on latitudinal climatic shifts and atmosphere-ocean interaction suggests some similarities between the patterns of climate in the 1960s and the climate of the Little Ice Age.
In Wisconsin, the growing season became cooler and shorter from 1958 into the mid-1960s. These trends accompanied a pronounced drop in the mean annual tropospheric temperature of the Northern Hemisphere. Although Northern-Hemispheric—tropospheric temperatures continued to fall (albeit at a lesser rate) from the mid-1960s through 1973, the growing season in Wisconsin showed a general trend toward lengthening and warming. In view of concern over the potential impact of climatic variation upon agriculture, these observations point out the need for a detailed examination of the modes of translation of hemispheric—tropospheric temperature trends to climatic changes at ground level, and at smaller temporal and spatial scales.
42. Gates, 1976
Recorded data show that from 1940 to the early 1970s the average temperature in the Northern Hemisphere slowly decreased, with a net cooling of approximately 1°F [-0.55 °C] over the continents and less cooling over the oceans. We also know that during the period from about 1890 to 1940 the air over at least the continents of the Northern Hemisphere underwent a gradual warming of over 1.5°F [+0.83°C]. … Whether such a cooling can actually be attributed to man-made aerosols is, however, now in doubt, and it is interesting to note that since the 1970s the mean temperature of the Northern Hemisphere has shown an apparent upswing. Whether such fluctuations are primarily the result of man’s activities or are only natural climatic variations remains an open question. … From historical records we also know that similar climate fluctuations have previously occurred over at least portions of the earth. The time around 1000 A.D., for example, was one of unusual warmth in the North Atlantic and European region and was characterized by relatively mild winters over a period of several hundred years. This has been called the climatic optimum, and it coincides with the period Viking exploration and settlement of Greenland and North America.
Baffin Island is thus a critical area in which to monitor glaciologial and climatological changes. The processes that are involved may be taking the world toward the next full glaciation. chronology and related climatic changes of the island over the last 120,000 yr are of a global significance.
Mean summer temperatures have declined throughout the 1960s to a level cooler than for approximately 40 yr. … On a regional basis, winter precipitation has increased by more than 30% over the last 10 yr. Both the winter-warming trend and the increased precipitation are presumably related to a change in the frequency of southerly airflow types advecting warm moist air into the region. The net effect has been for heavier falls of snow in winter and with lower summer temperatures and therefore less melting (Jacobs et al, 1972), resulting in notably increased glacierization. … Recent field observations and comparisons with aerial photographs taken late in the ablation seasons of 1949 and 1960 provide verification of a recent climatic deterioration. Snowbanks decreased from 1949 to 1960 and expanded during the next 10 yr. In one case, a permanent snowbed overlay 25 mm thalli of the lichen Alectoria minuscula which indicate seasonally snowfree surface for the previous 40 ± 10 years. Additionally, at least two corries snowfree in 1960 are presently occupied by incipient glaciers. … The present Neoglacial ice is nearly as extensive as the late glacial stade (Figs. 2 and 3).
Of the various mechanisms suggested by which man might change the planetary climate, the removal of tropical rain forests to increase arable acreage seems to be one of the more imminent. For this reason we selected this as one of the first problems to be tested in our recently updated climate model. Bearing in mind the fallibility of computer simulations, we find overall global cooling and a reduction in precipitation: a larger tropical reduction being almost balanced by a subtropical increase.
In recent decades, however, a general cooling has been apparent in high latitudes. In northeast Greenland this appears to have been of the order of 0.3°C for the period 1940 to 1959
Conclusion (last paragraph): Since the fifties the decline of temperature and the increase of precipitation have been the predominant trend in the western part of China. According to the dendroclimatological data obtained from several places, the declining temperature trend will continue till the end of this century or the beginning of the next [late 1990s to early 2000s]. From this we predict that the number of advancing glaciers may increase considerably in the days to come. But the relation between the fluctuations of glaciers and the changes of climate is very complex. The law ruling the fluctuations of glaciers is still left to a considerable extent to the systematic study and observation of us all.
47. Ložek, 1972
The dwindling formation of tufa spring deposits and their partial destruction both in occupied and unoccupied areas indicate that the Holocene warm interval is in the late phase. The recent slope deposits are reminiscent of early glacial sections both by their lithology and fauna reflecting existence of large open spaces. Whereas in early glacials the deforestation resulted from the change of climate, the recent one is almost entirely a product of man.
Theoretical considerations and empirical evidence indicate that atmospheric turbidity, a function of aerosol loading, is an important factor in the heat balance of the earth-atmosphere system. Turbidity increase over the past few decades may be primarily responsible for the decrease in worldwide air temperatures since the 1940’s
49. Mitchell, 1971
Turning to the presumed effect of such large-scale background aerosol increases, a number of authors have called attention to the coincidence between these increases and a systematic decline of worldwide average temperature in the past two or three decades, and have considered the possibility of a causal connection between the two phenomena (McCormick and Ludwig, 1967; Bryson, 1968; Budyko, 1969; Bryson and Wendland, 1970; Mitchell, 1970). … With particular regard to the recent cooling trend of worldwide climate, the attribution of this cooling (or any significant part of it) to secular increases in atmospheric particles from human activities now appears unlikely, not merely on quantitative grounds (see Mitchell, 1970) but on qualitative grounds as well. Indeed, long-term increases of particulate pollution of the atmosphere by man may serve to augment, rather than oppose, other warming effects of human activities, such as the increasing carbon dioxide content and direct thermal pollution of the atmosphere. In that event the observed climatic cooling of the past quarter century emerges more persuasively than ever as a natural geophysical phenomenon, with man the innocent bystander.
People are always interested in the weather and wonder if the climates of the world do actually change, at least during their lifetimes. James Michener (1976) asked “where did the animals go?”, writing about the extinction of our North American animals at the end of the “Ice Age.” Bryson and Murray (1977) wrote about “mankind and the world’s changing weather” and the “climates of hunger.” Kukla and associates (1977) presented “new data on climatic trends” and showed that during the last 30 years in the Northern Hemisphere, the oscillatory cooling has not yet reversed. Shultz (1972) reported on the northern migration of the armadillos and other southern vertebrates into the Kansas, Colorado and Nebraska region of the Great Plains during the 1930’s to 1950’s. Then there was a sudden reversal of the migration to the south during the 1960’s and 1970’s as cooling began to take place. The recent migrations, of course, were the result of minor climatic changes which often go unnoticed. Observations of the present climatic trends as well as those of the past are necessary if we are to interpret our environments of the future. We now know that climatic changes may happen at a more rapid rate than we had thought, but much more research must be done before accurate long-range climatic forecasting can be accomplished. Certainly man must be prepared to face climatic disasters and adjust to them.
Autumns in the Northern Hemisphere during the 1974–78 pentad were substantially cooler than in the pentad ending in 1938 [1934-’38]. Zonally averaged surface air temperature in October along latitude 80°N was 4.8°C lower, while summers were 0.6°C warmer. The recent pentad is cooler between 20 and 80°N in all seasons except spring when virtually no change was detected. The largest temperature difference was observed in autumn and winter in the high latitudes, which is a region of negative surface heat balance.
52. Norwine, 1977
Around 1900, a radically different climate stage set in, probably worldwide, one of warming (see Figure 1). … Well, all that was nice while it lasted, but a substantial cooling phase of deterioration has characterized the last 25 to 30 years
53. Reitan, 1974
Mean monthly temperatures for the Northern Hemisphere were determined for the years 1955 through 1968 following the same procedures used by H. C. Willett and J. M. Mitchell, Jr., in their studies of long-term trends. It was found that the downward trend they reported starting in the 1940s continued, though interrupted, into the 1960s. The temperature data when combined with radiation data and other components of the hemispheric energy budget led to the formulation of the response ratio, the relationship between change in incoming solar radiation and change in temperature. When this response ratio was applied to the reported trends in direct solar radiation and to the decrease in direct solar radiation following the eruption of Agung in 1963, a probable cause-effect relationship was suggested.
[A]bout 1000 years ago a relatively mild period permitted Viking exploration of the North Atlantic region. Several hundred years later, at the onset of the ‘little ice age,’ the Norse colonies in Greenland were wiped out, and the historical chronicles tell of long harsh winters that brought suffering and deprivation to Europe. Milder climate has returned in modern times, but the optimum (warmest) condition occurred in the 1940’s, and since then, there has been a fairly rapid cooling in the high latitudes of the northern hemisphere. The relatively benign climate that we have taken for granted in the latter half of the twentieth century is not characteristic of all periods since the retreat of the ice age. … Climate-induced famine is even more serious today. Already, 6 consecutive years of drought have ravaged large populations in parts of central Africa known as the ‘Sahel.’ The drought has left millions of people near starvation, and the number of deaths approaches hundreds of thousands. There are hints that the situation may yet worsen [e.g., Winstanley, 1973; Bryson, 1973].
An insolation chronology is introduced here, which is based entirely on astronomic factors (on the so called Milankovitch mechanism of Earth orbital elements). It is independent of any geologic or geochronologic dating systems. Two alternating units comprise the insolation chronology. The positive insolation regime (PIR) is an episode defined by progressively increasing winter irradiation in the Northern Hemisphere, whereas the negative insolation regime (NIR) is an episode of progressively decreasing winter irradiation. … It is observed that the positive insolation regime designated as PIR 110, which started at 11,000 YBP, has ended recently. The new negative insolation regime, NIR 0/ + 8, will last for the next 8000 yr. Inasmuch within the last radiometrically dated 150,000 yr no NIR is known to correlate with generally warm interval, the prognosis is for a long-lasting global cooling more severe than any experienced hitherto by civilized mankind.
If the Eemian is taken as the analog of the present interglacial, a point in time 116,000 YBP becomes the historical model for today’s ocean, and the North Atlantic is now approaching a time of severe cooling.
The effect of the atmospheric aerosol load on the earth’s climate has been of great concern during the past decade. McCormick and Ludwig (1967), Bryson (1968) and Mitchell (1970) suggested an increase of particulate loading would lead to a decrease in incoming solar radiation that would, in turn, lead to a general cooling of the earth’s temperature as observed during the past 30 years. Subsequently, other investigators (Charlson and PIlat, 1969; Mitchell, 1971) have suggested that the inclusion of the absorption effects of tropospheric aerosols could very well lead to a warming at the earth’s surface . It is generally agreed that stratospheric aerosols would lead to surface cooling, whereas uncertainty prevails about the consequences of an increase in tropospheric particulate loading. … Solar radiation has been monitored at Mauna Loa Observatory, Hawaii … since 1957. Since then there has been no significant change at Mauna Loa attributable to anthropogenic sources (Ellis and Pueschel, 1971).
Starr and Oort (1973) have made a comprehensive study of meteorological temperatures, using about 10 million individual measurements of temperature, to derive the average temperature of the bulk of the atmospheric mass in the northern hemisphere for each of the 60 months between May 1958 and April 1963. If the mean seasonal variation is subtracted from the monthly values to yield the residual temperatures, it is found that the spatially averaged temperature fell by about 0.60° C during the 5 years. A comparison of the temperatures with the monthly mean sunspot numbers during the same period suggests that the declining temperature trend may be associated with the decline in solar activity. This suggestion is supported by the fact that smoothed variations of temperature and sunspot number are both relatively flat during the first and last years of the 5-year period. Alternatively, it appears that Earth’s magnetic dipole is moving slowly into the northern hemisphere (Nagata, 1965) and the magnetic field is, on the average, gradually increasing there; this behavior may lead, in some unknown way, to the decrease of northern hemisphere meteorological temperatures.
59. Idso, 1982
A potential negative feedback relationship between atmospheric relative humidity and surface air temperature is described. Together with a recently proposed negative feedback mechanism involving atmospheric CO2, the phenomenon may be sufficient to prevent the global ice catastrophies which are a common prediction of many climate models following initial development of ice age conditions, and could well be of importance for the problem of the cool sun in Earth’s early history.
60. Chaston, 1980
Much of the Northern Hemisphere experienced a dramatic upsurge in snowfall during the 1970s as compared with the previoius decades. … Whether the “Snowy Seventies” heralded the dawn of a major cooling trend or is merely a temporary anomaly is highly debatable. One may ask fifty meteorologists for his/her opinion on climatic change and inevitably receive fifty differing opinions. This is why meteorology is so exciting: even with relatively advanced computer programs and the complete set of equations of motion of the atmosphere, we are far from truly understanding the mechanics of Mother Nature. What we do know is that, anomalous or not, the 70s saw a small fall in global temperature accompanied by a dramatic increase in Northern Hemisphere snowfall.
61. Skeeter, 1985
Numerous studies of global and hemispheric temperature trends have been undertaken in recent decades. One of the earliest studies was done by Willett in 1950. Willett analyzed temperature records of fifty years for 54 stations. He found that global temperatures increased 1°F (0.6°C) between 1885 and 1940. Winter temperatures during this same period were found to increase by 2.2°F (1.2°C). The most pronounced warming was in the high latitudes of the Northern Hemisphere. This warming trend conformed with the temperature trend that climatologists had expected to exist due to the increasing levels of carbon dioxide in the atmosphere. However, even though the amount of carbon dioxide in the atmosphere has continued to rise, cooling temperatures have been reported since about 1940. The first study to report this reversal in temperature trends was done by Mitchell in 1961. Mitchell updated Willett’s work through the 1950s and found that temperatures had fallen 0.2°C by the late 1950s from a peak in the early 1940s. In 1970, Mitchell stated that by the late 1960s global temperatures had fallen 0.3°C from the peak in the 1940s, approximately one-half of the prior rise. Similarly, Budyko reported that temperatures in the Northern Hemisphere fell 0.3-0.4°C between 1940 and 1976. Summaries by Schneider and Dickenson, Kalnicky, Robuck, Roberts, and Agee all report Northern Hemisphere temperatures declines by at least 0.5°C since the 1940s. In summary, Gribbin states “In worldwide terms, we are in a situation where the earth is cooling more quickly than it warmed up earlier this century. From the above it is clear that the general consensus in the recent literature is that there has been a cooling in the Northern Hemisphere since the early 1940s.
62. Arrigo, 1982
The decade of 1971-80 was 1.5°F cooler than 1931-40. The latest 40-year period of general cooling in annual values is a result of down trends in winter, summer, and fall seasonal temperatures
63. Lamb, 1966
The large-scale circulation of the atmosphere during the current decade has produced patterns that had never been seen earlier in this century, but which seem to represent a recurrence of a regime that prevailed over long periods before 1895. The decline of the temperature-zone westerlies and increased frequency of blocking in high latitudes have been associated with anomalies (or changes) of temperature and rainfall regime that are having serious effects in many parts of the world, and meteorology is being confronted with a demand for climatic forecasting for which no adequate scientific basis yet exists. Nevertheless, it is an urgent practical matter to take stock of the present climatic position and to assess the probability of the new climatic regime continuing –albeit subject to normal year-to-year and decade-to-decade variations. The investigation here reported of some of the gross features of world climatic behaviour since 1960 apparently discloses an abrupt return to conditions as they were before the well-known warming of climates in the early 20th century–indeed a reversal of the change of behaviour of the large-scale wind circulation that took place about 1895. Increased meridionality of the wind flow over extra-tropical latitudes has been accompanied by an opposite change in the intensified development of the narrow equatorial low-pressure zone. A few previous step-like changes of climate of similar magnitude can be found by surveying what is known of the climatic history of the last 1000 years, but they are rare and apparently never less than forty-fifty years (oftener 150-200 years) apart. On this evidence, something like the climatic regime of the years since 1960 should probably be expected to persist till the end of the century or beyond–provided that the climatic balance is not effectively tilted, inadvertently or otherwise, by Man’s activities nor by other natural phenomena such as volcanic dust or the lack of it. Though these questions cannot be confidently answered at the present time, the economic stakes for most forward planning are so great that they pose a responsibility on thinking men. There is a case for a research group specifically directed to improving our knowledge in this field: to widening, and lengthening in time, our knowledge of the facts of climatic history and of the processes and critical events that affect the behaviour of climate over long periods.
64. Gordon, 1981
Lichenometric dating suggests that the maximum recent extent of cirque and small valley glaciers occurred before about A.D. 1850, although there is evidence for more extensive valley glacierization before about A.D. 1745. Between about 1850 and about 1968/69 progressive recession of the glaciers was interrupted by brief periods of reactivation during the 1880s, 1920s, and early 1940s. Since about 1968/69 the glacier fronts have advanced by up to 158 m following a marked climatic recession [cooling] during the 1960s and early 1970s. In general, fluctuations of the glaciers have been in sympathy with prevailing climatic trends and show a relatively rapid response following temperature changes and a lagged response of at least 9 yr following precipitation changes. Fluctuations of larger valley and icefield outlet glaciers are out of phase with the others which may reflect a greater time lag of 20 to 30 yr in their response to precipitation changes.
Between May 1958 and April 1963 the mean temperature of the atmosphere in the northern hemisphere fell by about 0.60° C.
Van Loon and Williams (1976) suggest that regional trends in surface temperature are indeed connected with long wave circulation changes, that the greatest variations appear above 500 N. latitude, but that the changes may be compensated for in other regions. For example, during 1942-1972 there appears to have been a change of -1.4°C in the mean temperature above 600 N. latitude but this appears to have been offset by a +0.20°C change over the area between 300 N. to 300 S. latitude. Budyko and Asakura (in NAS, 1975) show that for the period 1880-1969, average temperature for the northern hemisphere attained a maximum around 1940 and decreased until 1969. More recent records, however, indicate the decrease has leveled off and during the last 5 years and there has actually been little change. Budyko-Asakura’s average temperature data for the northern hemisphere (Figure 2) shows the range of change between 1880 to 1940 to be approximately 1.1°C.
67. Barry, 1977
The Greenland temperature records are of considerable interest (Figures 1 and 2). Winter (September through May) temperatures rose intermittently from about 1890 to 1930-1940 resulting in an overall increase of 4 to 5°C. The warming was especially pronounced in the 1920s. Some cooling has occurred since 1930-1940 although temperatures in the 1960s are still approximately 3°C above those of the 1880s. Summer (June through August) temperatures show similar trends to those in the winter months. Again there is a marked warming between 1918 and 1928 and this has been reported in many other parts of the Arctic – Eurasia (Petrov, 1959, Iceland (Stefansson, 1969), Baffin Island (Bradley, 1973), Ellesmere Island (Hattersley-Smith, 1963), and in some records from Alaska (Hamilton, 1965). The dominant circulation regime over the Northern Hemisphere changed from meridional (north/south) to zonal (west/east) about 1917 (Dzerdzeevski and Sergin, 1972), giving rise to the observed warming trends, and this mode continued until the early 1950s, when a reversal [cooling] took place. … Cooling over the eastern Arctic in the summers of the 1960s was pronounced, leading to lower temperatures than for 30 to 40 years in Baffin Island. … [I]n the early 1970s there was evidence that snowbanks, identifiable on aerial photographs of the Cumberland Peninsula, Baffin Island, taken in 1959, had become much more extensive as a result of increased winter snowfall and reduced summer snowmelt. Although such growth may easily be reversed by a single warm summer, the pattern is suggestive of what may happen more persistently during a prolonged phase of climatic deterioration. The cooling observed over Baffin Island during the 1960s and early 1970s appears to be closely related to shifts in the standing waves in the hemispheric westerly circulation reported by Namias (1969, 1970). … Air reconnaissance data for the last two decades shows that between about 1963 and 1972 there was a significant increase in the severity of [sea] ice conditions for July through September in Baffin Bay (Dunbar, 1972). This apparently matches without any lag the cooling (up to 1972) in the eastern Canadian Arctic noted by Bradley and Miller (1972).
Lamb (1966) had already suggested that it appears likely that we have passed the height of the warming episode in the first half of this century and are now reverting to a pattern characterized by lower zonal flow and intensification of the trough/ridge systems, essentially a reestablishment of the climatic character of the last century.
69. Thompson, 1977
Recent theoretical studies (Pollack and others, 1976) and empirical evidence (Newell, 1970) indicated that variations in the concentration of particles in the atmosphere is an important component in the heat balance of the earth-atmosphere system. Some investigators (McCormick and Ludwig, 1967; Bryson, 1968; Rasool and Schneider, 1971) attributed the decrease in mean air temperatures of the northern hemisphere since the 1940’s to an increase in the atmospheric aerosol load. It is generally agreed that the effect of high altitude aerosols, such as stratospheric dust veils of volcanic origin, is theoretically one of surface cooling; however, the role of aerosols concentrated in the lower troposphere in the radiation budget is still open to speculation. Neumann and Cohen (1972) predicted net cooling as the end result, while Charlson and Pilat (1969) predicted net warming. … Mitchell (1975) found a correlation between an increase in the quantity of volcanically-injected stratospheric material and a decrease in mean temperatures in the northern hemisphere for the period since 1880 A.D.
70. Absolon, 1972
The present assemblages of Ostracods in Central Europe resemble the assemblages known from the earliest phases of Holocene. This observation supports the view that the termination of the present warm interval is to be expected in the near future.
71. Lentfer, 1972
Several authors have presented data indicating that sections of the Arctic have experienced warming trends prior to about 1950 and have experienced cooling trends since that time. Zubov’s (1943) data show a warming of the Arctic for approximately 100 years prior to publication in 1943. He shows that Arctic glaciers have receded and the southern boundary of Siberian permafrost has moved northward. Zubov also present comparative data obtained during the drift of the ‘FRAM’ and the drift of the ‘SEDOV’, 43 years later, over similar tracks in the Eurasian sector of the Arctic Ocean. The mean ice thickness was one-third less and the mean air temperature 4°C higher in 1937-40 than in 1893-96. Dorf (1960) quotes Willett (1950) who states that in Spitsbergen mean winter temperatures have risen about 8°C between 1910 and 1950. Dorf (1960) also quotes Ahlmann (1953) who reports ice free ports in Spitsbergen to be open to navigation about 7 months of the year as compared with only 3 months 50 years earlier. Mitchell (1965) states that world climate during the past century has been characterized by a warming trend from the 1880’s to the 1940’s. Thereafter, the warming trend appears to have given way to a cooling trend that has continued to at least 1960 with some evidence that it was continuing in 1965.
72. Palmer, 1973
This article reviews the information on the climatic effect of carbon dioxide and aerosols and outlines man’s part in contributing to their occurence. Recent downward trends in the average surface temperature of the biosphere has lead some scientists to conclude that albedo increases due to the effect of aerosol backscatter is the causative mechanism. While there is evidence for and against this hypothesis, this paper emphasizes that albedo changes due to aerosol modification of cloud cover may be a more significant mechanism for explaining temperature trends.
Between 1958 and 1965 there was a significant cooling averaging about 0.3°C over much of the globe, but since 1965 the temperature variations have been small.
The authors of this paper show, based on some examples from climatic history, that climate can change rapidly and that these changes can have drastic effects on world food production, as well as on other aspects of economic and cultural life. The historical examples are the Arctic expansions of around 1900 B.C. and A.D. 1200. The authors also describe a presently occurring Arctic [ice] expansion and its world-wide effects on climate to date.
75. Newell, 1974
Changes in the poleward energy flux by the atmosphere and ocean as a possible cause for ice ages
It is proposed that the two preferred modes of temperature and circulation of the atmosphere which occurred over the past 100,000 yr correspond to two modes of partitioning of the poleward energy flux between the atmosphere and ocean. At present the ocean carries an appreciable fraction of the transport, for example about three-eighths at 30°N. In the cold mode it is suggested that the ocean carries less, and the atmosphere more, than at present. During the formation of the ice, at 50,000 BP, for example, the overall flux is expected to be slightly lower than at present and during melting, at 16,000 BP, slightly higher. The transition between the modes is seen as a natural imbalance in the atmosphere-ocean energy budget with a gradual warming of the ocean during an Ice Age eventually cluminating in its termination. At the present the imbalance is thought to correspond to a natural cooling of the ocean, which will lead to the next Ice Age.
76. Wahl and Bryson, 1975
Recent changes in Atlantic surface temperatures
Rodewald recently published brief notes about the temperature measurements of the sea surface made by nine North Atlantic weather ships during the past two decades. His remarks were prompted by the regrettable fact that several of these ocean stations are being discontinued, a decision which will make it much more difficult to monitor the temperature trends in the North Atlantic. He presented average annual temperature values for overlapping 5-yr periods, showing a distinctive decrease of 0.56 °C from the 1951–55 period to the 1968–72 period
77. Gordon, 1980
Recent climatic trends in the Arctic have been characterised by a general cooling between the mid-1950s and the late-1960s, followed by a return to warmer conditions in the early 1970s (refs 1,2). Throughout the Canadian Arctic Archipelago and at Thule in north-west Greenland a marked decrease in summer temperature occurred after 1963, and winter precipitation increased. These changes were accompanied by a lowering of the average July freezing level height by as much as 500 m (ref. 5), decreased glacier mass loss and increased glaciation. Here I report similar climatic trends in West Greenland and demonstrate different glacier responses, in particular an advance of cirque and small valley glaciers since about 1968, contrasting with a simultaneous retreat of larger valley and icefield outlet glaciers.
78. Williams, 1978
It has been suggested that the Laurentide Ice Sheet originated with extensive perennial snow cover, and that the snow cover affected climate so as to aid ice-sheet development. In this study, a large increase in extent of October 1st snow cover in the Canadian Arctic from 1967–1970 to 1971–1975 is compared to changes in October means of other climate variables. Over the area of snow-cover expansion, mean surface air temperature decreased by up to 3°C, mean 500-mbar height was lowered by over 60 m, and precipitation was increased by up to a factor of two. These effects, if applied to the entire summer, together with the temperature change computed by Shaw and Donn for a Northern Hemisphere summer insolation minimum (the Milankovich effect), can account for glacierization of the Central Canadian Arctic.
79. Barrett, 1971
Changes in concentration of those atmospheric constituents which contribute to the planetary albedo can give rise to climatic alterations. … These computations show that substantial depletions of irradiance can result from moderate to heavy particulate loadings, and that an increase in man-made particulate emissions by a factor of 50 or more could give rise to a general cooling of serious magnitude.
80. Mörner, 1972
When Will the Present Interglacial End?
We are now living under interglacial climatic conditions, the Present Interglacial of Flandrian Interglacial Age. It will certainly be followed by the Future Ice Age. The major cold/warm changes seem to have a cyclicity of 10,500 years. We have been in the 2nd cycle (characterized by a cooler climate) after the Last Ice Age for 2200 yr and will continue to be so for another 8300 yr. … ADDENDUM BY AUTHOR Several articles in this volume provide material strongly in favor of Alternative II of Fig 1. This would mean we are now rapidly approaching a future situation equivalent to the “Pre-Brörup Stadial” (cf. Fig. 2), characterized by continental glaciation over Fennoscandia and the Kolar Peninsula and tundra or park-tundra conditions in most of the rest of Europe (the”Pre-S. Pierre Stadial” of North America was similarly characterized by continental glaciation over northeastern North America and alpine glaciations in the mountain regions of the West Coast).
81. Miles, 1978
The cooling of the Northern Hemisphere since 1940 has been variously interpreted as the overture to the next Ice Age, the effect of industrial pollution in the atmosphere or of a decline in the solar output. Are we in a position to judge between these various interpretations and to make a prediction for the next few decades? The link with the next Ice Age may be dismissed as a confusion of timescales; the explanation in terms of atmospheric pollution merits careful examination but seems unlikely to be adequate on its own. Natural fluctuations must also be considered.
Dewey and Heim (1981) have studied variations in N.H. seasonal snow cover based on satellite observations and have found that there was an overall increase in snow-cover area from 1966 to 1980. They also noted that there has been a trend toward earlier, more extensive snow cover in the fall and slower ablation in the spring. Their observations are supported by the results of a model study conducted by Choudhary and Kukla (1979) where-in they noted that the addition of more CO2 to the atmosphere could significantly reduce the shortwave energy absorbed at snow and ice surfaces and thus delay the recrystallisation of snow and dissipation of pack-ice, resulting in a cooling rather than a warming effect. They additionally noted that this process may contribute to an extension of snow and ice seasons marked by delayed snowmelt in spring, and early snow deposition in autumn. Thus, during the last 3 decades, larger winter cooling anomalies, supported by observations and model studies, have greatly influenced the climate pattern – made it cooler and unstable.
83. Borisov, 1969
Can We Control the Arctic Climate?
Soviet climatologists are vitally concerned with the problem of ameliorating the climate of Siberia and other northern lands as a means of developing these regions for an expanding population. P. M. Borisov, a candidate in geographic sciences, Moscow, examines one means of warming the climate by the transport of Atlantic Ocean water across the Arctic Basin. This could be done by pumping water out of the Arctic Ocean at the Bering Strait, thus accelerating the flow of warmer Atlantic water into the basin. Flow direction would be controlled by means of a dam across the Bering Strait. Borisov predicts dramatic improvement in Arctic climate would result. Huge areas of permafrost would be freed for agriculture in northern Canada and Siberia. Grass would grow in the Sahara Desert. This article, appearing first in the Soviet journal, Priroda, was translated by the Canadian Defence Research Board. It is reprinted here through the courtesy of the Board and by special permission of the editors of Priroda.
[Climatologists were concerned/interested in warming the climate via geoengineering in 1969. ]
84. Flecher, 1969
The post-glacial warming culminated in the “climatic optimum” of 4000-2000 BC, during which world temperatures were 2-3°C warmer than they are now …Since the “little ice age” of 1650-1840, which climaxed the cooling trend from about 1300, a new warming trend predominated which seems to have reached a climax in this century, followed by cooling since about 1940, at first irregularly but more sharply since about 1960.
SPECIFIC SCHEMES FOR CLIMATE MODIFICATION
Ice Free Arctic Ocean The largest scale enterprise that has been discussed is that of transforming the Arctic into an ice free ocean. As was noted earlier this has been most carefully studied by the staff of the Main Geophysical Observatory in Leningrad. … It is possible that the capacity of present technology may be sufficient to accomplish this task. but this has not been established. Three basic approaches have been proposed (Fletcher 1965): (1) influencing the surface reflectivity of the ice to cause more absorption of solar heat; (2) large scale modification of cloud conditions by seeding; (3) increasing the inflow of warm water from the Atlantic.
Bering Strait Dam Soviet engineer Borisov (1959, 1967) has been the most active proponent of the much publicized Bering Strait Dam. The basic idea is to increase the inflow of warm Atlantic water by stopping or oven reversing the present northward flow of colder water through Bering Strait. The dam would be 50 miles long and 150 feet high.
Deflecting the Kuroshio Current The Pacific Ocean counterpart of the Gulf Stream is the Kuroshio Current, a small branch of which enters the Sea of Japan and exits to the Pacific between the Japanese islands. It has been proposed that the narrow mouth of Tatarsk Strait be blocked by a giant “water valve” to increase the warm inflow to the Sea of Okhotsk and reduce the winter ice there.
[Scientists at the time were considering geoengineering “schemes” that may facilitate climate warming.]
85. Battan, 1970
This article give a brief review of Soviet articles on weather modification published since about 1964. … Budyko (1964) examined various questions dealing with climate modification. He noted that the melting of the arctic ice would have important effects on climate and stated that there are a number of ways by which the arctic ice cap can be annihilated. He cited several proposals for doing it and ruled them out as ineffective or not practical. He proposed that some schemes which would not be effective over the entire Arctic could be used successfully in the Norwegian and Barents Seas and over a period of years cause sufficient warming of the Arctic Ocean to melt the ice in the arctic. If the ice were removed, according to his calculations, air temperatures in the arctic would increase by 5-10C and 15-30C in the summer and winter, respectively.
Borisov (1967) apparently is still trying to sell the idea of building dams across the Bering Strait (74 km wide and 54 m deep) and pumping cold Arctic Ocean water into the Pacific Ocean. He stated that by pumping at a rate of 145,000 km3 year -1 for about three years, sufficient warm water from the Atlantic would have entered the arctic basin to eliminate the arctic ice. He predicted the climate would begin to “improve” [due to warming] the first year. In a later paper Borisov (1969) painted a rosy picture of the consequences of arctic warming. He claimed that a study of the last climatic optima some 4000-6000 and 11,000-12,000 years ago, he could infer the consequences of arctic warming. He further suggested that in the first stage of partial melting of arctic ice there would be conditions resembling the “small” climatic optimum during the 9th and 10th centuries [Medieval Warm Period]. When this happens, it is claimed, winters will become less severe, the growing season will be lengthened, the probability of early autumn and late spring frosts will be decreased, the number of arid years will be decreased and the northern boundary of many types of vegetation will be shifted northward.
86. Hollin, 1969
Wilson suggests that in the Pleistocene the surge coolings were sufficient to trigger the northern ice ages. If so, interglacial pollen profiles should show rapid but temporary marine transgressions beginning at the break of climate. Evidence suggesting such transgressions occurs in England and the United States, but is still insufficient to disprove explanations such as local downwarping. There is no evidence yet for surges in Wisconsin or Post-glacial time. There is some evidence that the Antarctic Ice Sheet is currently building up, but this could be a response to a Post-glacial accumulation increase rather than the prelude to a surge.
87. Holdren and Ehrlich, 1971
Global Ecology: Readings toward a rational strategy for man [pgs. 76,77]
It seems, however, that a competing effect has dominated the situation since 1940. This is the reduced transparency of the atmosphere to incoming light as a result of urban air pollution (smoke, aerosols), agricultural air pollution (dust), and volcanic ash. This screening phenomenon is said to be responsible for the present world cooling trend—a total of about .2°C in the world mean surface temperature over the past quarter century. This number seems small until it is realized that a decrease of only 4°C would probably be sufficient to start another ice age. Moreover, other effects besides simple screening by air pollution threaten to move us in the same direction. In particular, a mere one percent increase in low cloud cover would decrease the surface temperature by .8°C. We may be in the process of providing just such a cloud increase, and more, by adding man-made condensation nuclei to the atmosphere in the form of jet exhausts and other suitable pollutants. A final push in the cooling direction comes from man-made changes in the direct reflectivity of the earth’s surface (albedo) through urbanization, deforestation, and the enlargement of deserts. The effects of a new ice age on agriculture and the supportability of large human populations scarcely need elaboration here. Even more dramatic results are possible, however; for instance, a sudden outward slumping in the Antarctic ice cap, induced by added weight, could generate a tidal wave of proportions unprecedented in recorded history.
88. Kalnicky, 1974
The mean temperature for the Northern Hemisphere had a warming trend from 1890 to 1950 and a cooling trend since 1950. The eastern and central United States had colder temperatures in 1961–1970 than in 1931–1960. The temperature changes were associated with an adjustment of hemispheric circulation from more frequent zonal flow between 1900 and 1950 to more frequent meridional flow since 1950. Regional variations in magnitude and direction of the change were largely related to position in relation to the upper air westerly wave pattern. Time series of individual circulation indices tend to resemble the step function model of climatic change.
89. Kotlyakov, 1980
His latest results (Kukla et al., 1977) indicate clearly a cooling of most of the Northern Hemisphere in the period from 1950 to 1975, reaching 0.1-0.2°C per decade (Fig. 3).
Fluctuations of the global climate have been one of the most interesting problems in meteorology. Recently the concern for this problem is increasing in relation to the possible climatic impact by man-made global air [aerosol] pollution. … Several attempts to estimate global temperature conditions have been successfully made by the use of meteorological network data. With long-period data from more than 100 stations, Willett had obtained the zonal mean of the surface air temperature for respective 10-degree latitude zone, avoiding the overweight in region of dense networks, such as Europe and North America. With these zonal mean temperatures at each latitude, the global mean temperature was computed. By Willett’s method, Mitchell presented the trend of the global mean of the surface air temperature, which shows a warming from the decade of 1880 to that of 1940, and afterwards cooling. A similar trend for the Northern Hemisphere was also given by Budyko, using maps of temperature anomaly, although the manner of constructing the maps was not described in his paper. Reitan shows a similar trend of the North Hemisphere temperature until the middle of the decade 1960, with the use of Willett’s method.
It is now generally accepted that the mean surface air temperature over the landmasses of the Northern Hemisphere, averaged over the year, rose by ~0.7°C from 1880 to ~1940 and then fell by ~0.2°C by the 1960’s. … The warming [since the mid-1960s] has, however, only resulted in a return to temperature levels of the late 1950’s and early 1960’s, and must, at present, be considered short term (Wigley et al., 1981). It could represent a temporary halt in the long-term cooling trend; the beginning of a period of relatively stable, i.e., trend-free climate; or the beginning of a long-term warming trend.
The 1880’s [in the Arctic] was the coolest decade during the study period, and was followed by a warming of 0.65°C to the 1900’s. Cooling then occurred; the average temperature during the 1910’s was ~0.45°C below the 1900’s. This cooling is less noticeable in the Northern Hemisphere average temperature d. Rapid warming affected the Arctic during the late 1910’s and 1920’s, with the average temperature peaking during the late 1930’s. A warming of ~1.60°C occurred between 1917 and 1921. While the average temperature of the Arctic was at a maximum in the 1930’s, the average temperature of the Northern Hemisphere was greatest in the decade of the 1940’s. After the 1930’s, temperatures fell: a drop of 0.85°C occurred up to the 1960’s.
92. Benson, 1962
A revised estimate for the balance of the ice sheet gives a slightly positive balance which is interpreted to mean that the Greenland ice sheet is essentially in equilibrium with present-day climate.
93. Eichenlaub, 1971
Evidence derived from the carefully screened temperature record at Eau Claire, Mich., and from radiosonde data at Sault Ste. Marie, Mich., supports the conclusion of Wahl and Lawson that a return to the temperature and circulation features of the early and mid-19th century in the eastern United States may be underway. Cooling trends at Eau Claire during the most recent decades have been accompanied by progressive lowering of the 700-mb surface at Sault Ste. Marie, and increased cold air advection into the southern Great Lakes area.
Definite cooling tendencies appeared in summer and winter, particularly during seasonal extreme months of July and January. Figure 2 shows 10-yr moving averages of monthly temperatures for June, July, and August. All 3 mo[nths] show temperature declines since the height of the recent climatic optimum during the 1930s. July temperatures have decreased about 3.5°F since the decades beginning with the early 1930s, and August temperatures have decreased about 3°F since the decades beginning with the late 1930s and early 1940s. … winter temperatures have decreased markedly since the late 1940s and early 1950s
94. Schultz, 1972
The nine-banded armadillos (Dasypus novemcinctus) have been moving northward in the Great Plains region from the late 1800s to the 1950s but now seem to be retreating from their lately acquired northern range. The armadillos have a nontypical homoiothermic blood system which makes them fairly vulnerable to cold climates. Many other adjustments of animal ranges have taken place in the Holocene, even during the past few centuries and evidence indicates that in many cases climate changes played an important role.
95. Landsberg, 1976
Howard A Wilcox (1975) [in his book] Hothouse Earth, has both polar ice caps melting as a result of heat rejection from human energy consumption; the second [book], by Nigel Calder (1975), The Weather Machine, warns of an imminent ice age. That leaves us where we were before; both can not be right. … The basic model Wilcox adopts is the Budyko-Sellers radiation equilibrium concept, slightly modified. He discounts feedbacks, has no concept of the role of the oceans, and leaves out all transport and eddy dissipation effects. Where the climatologists have cautiously and conservatively made tentative calculations with 1-2% changes in the solar “constant,” Wilcox regales us to an energy rejection equal to the present solar energy income by about the year 2200. He generously omits the evidently minor concomitant CO2 effects [as a factor affecting warming]. Perturbingly, there are nowhere real error limits placed on any of the estimates.
Calder’s book takes us to the other extreme. He gives a composite word picture that inexorably leads to an ice age. Mr. Calder is a science writer, who bases his views essentially on talking to scientists and reading literature selectively. Thus the book essentially is a review. … Calder’s vivid portrayal of catastrophic weather events are a tribute to him as a writer, but the conclusions he draws from them are very shaky. Of course, we are all very distressed by the human consequences of such events as the Sahel drought or the damages wrought by hurricane Agnes, but are they really indications of climatic change [global cooling]? … [I]n talking about the Indian monsoons he clearly advocates that these have become weaker and will be further weakened by a cooling of the earth; he then disparagingly quotes the Indian Meteorological Service stating that there are no trends in rainfall in the subcontinent corresponding to global warming or cooling. … He also reads from the record of the cores that ice caps can swoop down on us suddenly. For this he coins the term “snowblitz,” a rapid extension of the snow cover that will not melt in the summer. So we shall be frozen out at latitude 50°N, by his own calculations (without error limits), in the next century or two.
CONTINUE TO PART 2 HERE