Verification done: “consensus” on the ice age?

“We are currently experiencing global warming. But in the 1970s, apparently, scientists were saying we were heading for a small ice age. Can we know if this was indeed the case and why scientists believed it? “Asks Denis Pelletier, of Quebec City.
FACTS

This is a common argument among climate scientists: the current scientific consensus on global warming does not mean much, they argue, since there has already been a scientific consensus on the contrary in the 1970s, when point that some predicted a new glaciation. So it’s worth it to linger.

In the 1960s and 1970s, climatology was still a very young discipline that had to work with much more limited resources than nowadays – few satellites, shorter and fewer data sets, and so on. At that time, the researchers were aware that there had been global warming since the middle of the XIX th century, but the trend was reversed and the climate seemed to cool for a few decades. Indeed, between the early 1940s and the mid-1960s, global average temperature dropped 0.4 ° C and will not return to previous levels until the 1980s .

The idea that this cooling would continue in the long term, however, has never rallied enough scientists to speak of a “scientific consensus”, far from it. At the time, we knew the heating power of CO 2 and we knew that its concentrations increased in the atmosphere, but we also knew that industrial pollution also contained huge amounts of fine particles and aerosols that block the sun’s rays and send them back to space, which has a cooling effect. The question then was whether one of these two effects would prevail in the long term, and which one.

In a short history of the climatology of the time published in 2008 in the Bulletin of the American Meteorological Society (BAMS), three climatologists have reviewed all the studies on the subject published between 1965 and 1979. They found seven that were in favor of cooling, 20 who were neutral and 44 who felt that the warming trend would resume in the future. They also counted the number of citations collected between 1965 and 1983 by each of these articles in order to measure their influence in the scientific community, but this did not really change the picture: 325 citations for articles in favor of cooling, 424 for neutrals and more than 2000 for warming.

Note that the Watts Up With That climate-sensitive website challenged these figures and resumed the exercise in its own way. This site is certainly not as credible a source as BAMS and one can / must doubt its conclusions, but it is quite telling that its author could not find “better” than 86 articles leaning for cooling, 58 neutrals and 45 for warming for the period 1965-1979 . It’s a sign that even putting things to the worst of the worst (and perhaps even putting a grain of bad faith, something that Watts Up With That, a highly oriented site, has often been accused of doing in the past), we still can not say that there was a “consensus” on global cooling. The idea has been debated in science – it’s the farthest we can possibly go. And again, I repeat, not if we rely on the best sources, such as BAMS and credible sites like RealClimate.org and the NASA website .

What seems to have happened between 1940 and 1970, reads a summary of the scientific literature published in 2012 in this same BAMS is that the end of the Second World War marked the beginning of a period of rapid global economic growth, which has been accompanied by a sharp increase in pollution (and therefore cooling aerosols). Several strong volcanic eruptions, which also emit large amounts of these aerosols, have also occurred.

From the 1980s, however, Western countries adopted laws to reduce their emissions of these particles and aerosols (especially to reduce acid rain), so that their cooling effect has largely disappeared, leaving more room for the effect of CO 2 . The long-term trend of warming then resumed. Since the 2000s, however, we have seen that in India and China solar radiation is increasingly blocked, because of the strong economic growth of Asia, its dependence on coal and the resulting pollution. .

Lastly, both in the 2008 BAMS article and in other sources , the media have been instrumental in creating and sustaining the “myth” around the scientific consensus on cooling. In the 1970s, Science Digest’s , for example, titled, “Prepare for a New Ice Age”. Newsweek spoke of a “cooling world” and suggested a possible “dramatic decline in food production”, and many other articles spoke (abusively) of “precursors of glaciation” that accumulated.

In short, everything indicates that the media of the time saw there a narrative plot selling and they granted him much more space than it deserved.

False. It can not be said that “the” scientists predicted global cooling in the 1970s. Some did, yes, the idea was debated. But it has never been more important than the media of the time and that the climateosceptics of today have granted it. And it has since been abandoned by an overwhelming majority of climatologists.

The statement of a minister seems doubtful to you? Circulating information seems exaggerated, unfounded? Write to our reporter ( [email protected] ). The section “Verification made” will take the time to delve into the facts, in depth, to give you the right time. Because we either do not like false news.

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