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National Academy of Sciences (1975): “We do not know what causes…climatic change”

By Kenneth Richard

After having switched from warning the masses in the 1970s about imminent human-caused global cooling to warning the masses in the 1980s about an imminent human-caused global warming , the late Dr. Stephen Schneider suggested that, to avoid “potentially disastrous climatic change,” scientists should consider offering up “scary scenarios” so as to “capture the public’s imagination.”

Dr. Stephen Schneider via Discover, pp. 45-48, Oct. 1989:

On the one hand, as scientists we are ethically bound to the scientific method, in effect promising to tell the truth, the whole truth, and nothing but — which means that we must include all the doubts, the caveats, the ifs, ands, and buts. On the other hand, we are not just scientists but human beings as well. And like most people we’d like to see the world a better place, which in this context translates into our working to reduce the risk of potentially disastrous climatic change. To do that we need to get some broad based support, to capture the public’s imagination. That, of course, entails getting loads of media coverage. So we have to offer up scary scenarios, make simplified, dramatic statements, and make little mention of any doubts we might have.”

Notice how Schneider confirmed that an essential element in garnering “loads of media coverage” and “broad based support” is to “make little mention of any doubts we [climate scientists] may have.” Judging by media attention, this “strategy of advocacy” appears to have worked. After all, a growing percentage of the populace is now familiar with the claim that we can determine there is a 97% scientific consensus that humans cause climate change by selectively counting (and excluding) abstracts from scientific papers. In other words, expressing uncertainty or doubt about “disastrous climate change” caused by humans relegates one to classification with the claimed 3% fringe.

It didn’t used to be this way. Back in the 1970s and ’80s, or before there were strong government-sponsored incentives to link human activity to climate changes, it was still quite common for scientists to acknowledge that:

(a) climate parameters are extremely difficult to model because

(b) there are far too many unknowns in the climate system to determine cause and effect with confidence, and

(c) a discernable link between climate change and human activity is extremely difficult to establish.

For example, no less than the National Academy of Sciences (NAS) at one time definitively acknowledged that too little is known about the climate system to understand what causes climatic change. The summary of their position below is taken from the extensively-referenced 1975 NAS paper entitled “Understanding Climatic Change”. (National Academy of Sciences, 1975)

[T]he mechanics of the climatic system is so complex, and our observations of its behavior so incomplete, that at present we do not know what causes any particular climatic change to occur. … What we cannot identify at the present time is how the complete climatic system operates, which are its most critical and sensitive parts, which processes are responsible for its changes, and what are the most likely future climates. In short, while we know something about climate itself, we know very little about climatic change. Aside from local climatic effects, such as those due to urbanization, these studies have not yet established the existence of a large-scale anthropogenic climatic impact (Machata, 1973). Like their numerical simulation counterparts, such studies are made more difficult by the high levels of natural climatic variability and by the lack of adequate observational data.”

By no means was this expressed climate agnosticism by the NAS rare during that particular time period. Scientists routinely published papers in journals in the 1970s and 1980s that acknowledged a lack of understanding with regard to the main causes of climate change or the inherent limitations in climate modeling. In fact, some scientists described projections of future temperature changes in response to human activities an exercise in “the blind leading the blind.”

Other scientists acknowledged that it is “practically impossible to isolate simple cause-and-effect relationships in the internal workings of the earth-atmosphere-ocean system” or, succinctly, that we “should admit at once that we do not know what are the basic causes of climatic change“.

However, by the 1990s, or with the advent of the the United Nations issuing the first two IPCC reports (1990, 1995), these we-don’t-know concessions by scientists had begun to dissipate. Expressing uncertainty or doubt about the dangerous climatic effects of carbon dioxide has become increasingly taboo.

Even the editor of the journal Science (Marcia McNutt) has herself recently (2015) written that, with regard to human-caused global warming, “the time for debate has ended.” (Link: here). The uncertainty, doubt, and skepticism have essentially been shooed away, which has paved the way for “scary scenarios” to potentially “capture the public’s imagination” — just as Dr. Stephen Schneider had proposed.

With this contrast between then and now in mind, perhaps it would be interesting to read what scientists used to commonly write in scientific journals with regard to the immense uncertainties associated with climate change. Below are several prototypical examples from the time period when expressing a lack of understanding about the causes of climate change was still considered acceptable — or before scientific advocacy was normalized.

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1. Barrett, 1978

In particular, detection of an anthropogenic influence through statistical analysis alone requires a long run of data of good quality and careful attention to measures of significance. It is most important to avoid the post hoc ergo propter hoc fallacy that a trend of a few years’ duration or less, following some change in human activities, can be attributed to that change even when no sound physical causal relationship is evident. … While one must presume that natural climatic fluctuations result from the operations of the laws of physics and chemistry, it is practically impossible to isolate simple cause-and-effect relationships in the internal workings of the earth-atmosphere-ocean system. This is because all the processes are interconnected by multiple nonlinear positive and negative feedbacks.

2. Fletcher, 1968

What Causes the Global Climate to Change? 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. It follows that the fundamental problem in the study of climatic change is the development of a quantitative understanding of the general circulation of the atmosphere; and, since three-fourths of the heat which forces the atmospheric motion comes by way of the ocean surface, a quantitative understanding of oceanic heat transport and ocean/atmosphere heat exchange is especially vital. … An adequate theoretical basis has not as yet been developed for explaining the interactions of the global heat engine and for accounting for observed changes in climate. Causal relationships have been obscured by the multitude of factors operating and problems for investigation have often been ill-defined. … [T]here are so many variables and degrees of freedom in the global system that specific cause and effect estimates in this regard are very uncertain.

3. 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. … 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.

4. Gilchrist, 1983

Unlike some other pollutants introduced into the atmosphere by Man, carbon dioxide is naturally occurring and non-toxic. The direct effect of increased concentrations may be beneficial notably because it will tend to increase the rate of photosynthesis in plants. On the other hand, there may be deleterious effects through its influence on climate but this is still unproven and we cannot be certain whether, on a global scale, it will on the whole be harmful or beneficial. … The problem of determining the effect of increased carbon dioxide on climate is difficult, the more so because there are some essential aspects of the physical basis of climate that are not well understood

5. Catchpole, 1973

Sellers (1965, p. 198) regretted that while ‘the literature has been saturated with theories of climatic change . . . uncertainty is the only thing that is certain’. Crowe (1971, p. 471) conceded that although palaeoclimatology asks straightforward questions about the nature and causes of climatic changes, ‘the answers still largely elude us’. In the same year Flint (1971, p. 789) appealed that we should ‘admit at once that we do not know what are the basic causes of climatic change’.

6. Stewart and Glantz, 1985

[I]n 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. … 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.

7. Roberts, 1975

There are, of course, many different ideas about the origins of climate change. Many factors have been looked upon as potential causes: vulcanism, sea surface temperature changes, changes in CO2 content of the atmosphere, oscillations in Arctic ice and sea depth, and atmospheric turbidity changes due to manmade dust or wind-blown soil and sand. These theories, including the solar one, share the difficulty that they have not yet reached the stage where convincing experimental verification is possible.

8. Shutts and Green, 1972

Many theories about climate change are essentially untestable, but we can still develop a consistent model based on understandable physics—in fact the data cannot be interpreted without one. Shutts and Green believe there is some fundamental defect in all present models: it could be something physically improbable, like an unreasonable effect of tiny solar variations. More likely there is a fundamental lack in our appreciation of how very interactive systems behave.

9. 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.

10. Mac Cracken, 1982

Several recent studies have contended that the increase in CO2 concentrations since the start of the Industrial Revolution has led to identifiable climatic warming. Significant approximations and simplifications have had to be made, however, in order to isolate this supposed CO2 effect from the comparably large latitudinal and temporal temperature variations that may have been due to changes in volcanism, solar variability, other potentially identifiable causal factors, or natural fluctuations. To overcome the resulting uncertainties, data bases must be improved, diagnostic analyses and numerical models must more completely treat the spatial and temporal patterns and phase relations of the expected changes, and a careful search for a set of CO2-specific climate modifications must be undertaken.

11. Schneider, 1974

Unfortunately, knowledge of climate theory is still too primitive to trace reliably climatic cause and effect links, and therefore it is argued that large-scale climate modification schemes appear irresponsible.

12. Dyson, 1977

The magnitude of this negative feed-back effect of atmospheric CO2 upon itself depends on many ecological interactions which have yet to be disentangled. The effect could be negligibly small, or it could be as large as 3 x 109 tons of carbon per yr. In summary, there is insufficient evidence to decide whether the carbon content of the biosphere has decreased, increased or remained stationary in response to the manifold human activities of recent decades. There exists a huge literature attempting to assess or to prognosticate the effects of the increasing atmospheric CO2 on the climate of the earth. Such attempts are useful and necessary, but they run into formidable technical difficulties. Even the mean global temperature rise caused by a given quantity of CO2 is subject to great uncertainty: and the effects of CO2 on local and time-variable phenomena (which may be crucially important to agriculture and other human activities) are more uncertain still.

13. Oerlemans, 1982

Conclusion: This estimate is subject to a number of uncertainties. First of all, opinions about the effect of an increasing CO2 content of the atmosphere differ widely. It is generally accepted that a warming has to be expected, but its magnitude is subject to much debate. Even if we did know the effect of CO2 on climate, things would not be much clearer. The global carbon cycle is poorly understood and we are not yet able to predict (given the anthropogenic CO2 input) the content of the atmosphere for next centuries.

14. Meier, 1983

Should we expect a “threat of disaster” (Mercer, 1978) with sea level and climate in the next 50 years? The obvious answer is no; the complex ice/ocean/atmosphere system is not sufficiently understood. The West Antarctic Ice Sheet may be robust to rapid oceanographic or atmospheric forcing (Whillans, 1978). Unfortunately, we are not even sure whether its grounding lines are currently advancing or retreating, and we certainly do not understand how surges are triggered. Until such understanding is at hand, and atmospheric-oceanographic circulation models are developed that perform well at high latitudes, we can only watch what is happening.

15. Sachs, 1976

This test shows that patterns of climatic change can be resolved with increasingly greater detail but that ‘first causes’ of climatic change remain elusive.

16. Bryant, 1987

Conclusions: The scenario of a CO2-warming globe contains many uncertainties. The warming of the atmosphere is not an established fact, and even if it was there may be no need to invoke increased atmospheric CO2 or other ‘greenhouse’ gases as the cause when such warmings have been a part of our temperature time series historically. … A common factor underpinning our uncertainties about a CO2-warming atmospheric scenario is that the Earth is not covered adequately with enough data points to evaluate the scenario conclusively. Even where geophysical time series are available, they are clouded by the inherent fluctuations of their variances.