Dr Stephen Schneider is perhaps the most media-exposed Greenhouse expert, having developed a charismatic speaking style, complemented by his 1970s good looks, and penchant for extravagant claims about impending environmental disaster.

Such a comment was quite wrong, climatically speaking, and blatantly alarmist.

He is also a fully qualified climatologist, closely identified with climate modeling at the National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA. He has written numerous papers and articles on the subject and is invariably sought out by the media for the latest horror predictions about Greenhouse, due to both his willingness to cast scientific caution aside in making such predictions, and his natural articulate and charismatic appeal to the general public.

It would be fair to say that Schneider bears a large part of the responsibility for making Greenhouse the hysterical public issue it has become today. He even once joked that since Greenhouse had hit the public arena, he had become more of a politician than a scientist. (`Many a true word is spoken in jest')

That Greenhouse had moved from being an esoteric scientific issue to being a political one was certainly true, and Schneider was in the vanguard of the political push to get Greenhouse firmly implanted in the public consciousness.

Firstly, Schneider was not always promoting the idea of Global warming. Up to about 1978, Schneider was warning the world of an impending Global Cooling, leading to the next Ice Age !

Before Global Warming became the politically correct scientific fashion of the 1990s, the reverse situation existed in the 1970s, where it had become a scientific article of faith that the Ice Age was about to happen. Even the US National Academy of Sciences adopted this view.

Prof Patrick Michaels, now a prominent critic of the Greenhouse scare, was justifiably sceptical then, just as he is now.

Just as with Global Warming, we find Schneider in the vanguard of the Global Cooling doomsayers during the 1970s.

It was only when global temperatures took an upward turn around 1980 that Schneider and others quickly made a career change and became passionate advocates of impending catastrophe, only this time from warming, not cooling. But then, opportunism is a trait of politicians rather than scientists.

During the Ice Age Scare of the 1970s, Schneider was one of it's foremost advocates. He published a book titled "The Genesis Strategy" at this time, warning of the coming glaciation, and wrote glowing a testimonial on the back cover of a popular `Ice Age' book of the time - (Ponte, Lowell. "The Cooling", Prentice Hall, N.J., USA, 1976), in which the author claimed that the climatic cooling from 1940 to the 1970s was but the precursor to the main event - the coming Ice Age.

Schneider was one of the first in the scientific community to warn of the impending Ice Age with this paper -

Schneider S. & Rasool S., "Atmospheric Carbon Dioxide and Aerosols - Effects of Large Increases on Global Climate", Science, vol.173, 9 July 1971, p.138-141

Here are the opening paragraphs of that paper -

Abstract. Effects on the global temperature of large increases in carbon dioxide and aerosol densities in the atmosphere of Earth have been computed. It is found that, although the addition of carbon dioxide in the atmosphere does increase the surface temperature, the rate of temperature increase diminishes with increasing carbon dioxide in the atmosphere. For aerosols, however, the net effect of increase in density is to reduce the surface temperature of Earth. Becuase of the exponential dependence of the backscattering, the rate of temperature decrease is augmented with increasing aerosol content. An increase by only a factor of 4 in global aerosol background concentration may be sufficient to reduce the surface temperature by as much as 3.5 deg.K. If sustained over a period of several years, such a temperature decrease over the whole globe is believed to be sufficient to trigger an ice age.

The rate at which human activities may be inadvertently modifying the climate of Earth has become a problem of serious concern 1 . In the last few decades the concentration of CO2 in the atmosphere appears to have increased by 7 percent 2 . During the same period, the aerosol content of the lower atmosphere may have been augmented by as much as 100 percent 3 .

How have these changes in the composition of the atmosphere affected the climate of the globe? More importantly, is it possible that a continued increase in the CO2 and dust content of the atmosphere at the present rate will produce such large-scale effects on the global temperature that the process may run away, with the planet Earth eventually becoming as hot as Venus (700 deg. K.) or as cold as Mars (230 deg. K.)?

We report here on the first results of a calculation in which separate estimates were made of the effects on global temperature of large increases in the amount of CO2 and dust in the atmosphere. It is found that even an increase by a factor of 8 in the amount of CO2, which is highly unlikely in the next several thousand years, will produce an increase in the surface temperature of less than 2 deg. K.

However, the effect on surface temperature of an increase in the aerosol content of the atmosphere is found to be quite significant. An increase by a factor of 4 in the equilibrium dust concentration in the global atmosphere, which cannot be ruled out as a possibility within the next century, could decrease the mean surface temperature by as much as 3.5 deg. K. If sustained over a period of several years, such a temperature decrease could be sufficient to trigger an ice age!

It was clearly not enough to merely warn of an impending Ice Age, but he also blamed it's potential onset on human activities causing aerosol discharge into the atmosphere. After all, every disaster must have a scapegoat. In fact, aerosol discharge into the global atmosphere has not lessened in any way. It has, if anything, increased. This means that Schneider's conclusions would be just as valid today.

Note how he also discounted the countervailing effect of carbon dioxide, claiming that even an 8-fold, or 800%, increase in CO2 would give very little warming and would, of itself, raise temperature less than 2 deg. In view of the fact that CO2 has so far risen only 25% since the Industrial Revolution, this would suggest that Schneider saw little warming potential in CO2 at all - in 1971. This makes his later conversion to the gospel of CO2-induced Global Warming all the more inexplicable, given that atmospheric radiation physics are the same today as then.

In 1971, Schneider claimed that an 800% increase in CO2 would be needed to raise global temperature by +2 deg. By the late 1980s, he promoted the UN view that a mere 100% increase in CO2 would be enough to raise temperature by +1.5 to +4 deg.

In 1971, Schneider promoted the idea that the next Ice Age was imminent. By the mid-1980's and into the 1990s, he equally vigorously promoted the idea that world was about to suffer a catastrophe caused by Global Warming.

In both cases, Schneider was publicly active in promoting both views, wheras other scientists who may have had a change of view due to new information, did so in the relative privacy of the scientific community, avoiding unnecessary publicity. Not so with Schneider. He revelled in publicity, and promoted both viewpoints at different points in time with equal enthusiasm.

When Schneider uses his public profile to promote an idea, he is not only economical with the truth, as suggested by his comment to Discover magazine at the head of this article, but he also makes dramatic statements designed to create an impression with the public, but which on closer examination are shown to be quite misleading. Take, for example, the following quote from a TV interview he gave with Britain's Channel 4 in 1990 -

Technically, Schneider was quite correct here. We do know that cold times ( eg. ice ages) tend to associated with less greenhouse gases, warm time with more greenhouse gases.

But what impression was this comment designed to make on the general public (to whom it was directed)? Clearly, he was implying that greenhouse gases cause warm times, while a lack of these gases cause cold times.

Here is a chart of temperature and carbon dioxide going back 160,000 years, a period which includes the present warm period (Interglacial), the last Ice Age, and the previous Interglacial to this one. (data is derived from ice cores from Greenland and Antarctica, where gas content can be determined from trapped air bubbles in the ice, and temperature determined from the ratio of oxygen isotopes in those bubbles).

Schneider clearly intended the public to get the impression that the carbon dioxide was the villain, but closer examination of this graph shows that changes in temperature occurred before the associated change in carbon dioxide. In other words, it was the changes in temperature which caused the changes in carbon dioxide, not the other way round as hinted at by Schneider.

Other studies (eg. Kuo, Lindberg & Thomson, 1990) confirmed that changes in temperature do indeed cause carbon dioxide to vary. Schneider omitted to tell the public that when two variables correlate, the cause-effect relationship can go either way, or even be subject to an external variable.

Finally, on the key issue as to whether this century has yet seen a Greenhouse-induced warming or not, his scientific standards were perhaps best illustrated from his own lips during that same interview with UK Channel 4 in 1990 -