In April 2008 I delivered a paper to the ACT Division of the Planning Institute of Australia about the threat of global warming. Some months later we were to have the Copenhagen Climate Conference that was to solve all humanity’s problems. Many leaders said we had only a few weeks/months/years to save the planet. Al Gore, walking on stage to get his Nobel Peace Prize, barked to an interviewer that ‘the science is settled!’ Carbon dioxide in the atmosphere had been rocketing up, and so had seemed to be global temperature. So 2008 was a year where global warming was much on the national and international agendas. Our Prime Minister had already proclaimed that it was the most serious moral, economic and social challenge to humanity, or words to that effect.
My paper, which had grown out of a few years of close study of the issue, was profoundly sceptical of this apocalyptic talk. Yes, there might be something in it, but if you looked hard at the way the issue was set out you did begin to stroke your chin and shake your head. Above all, the data of all kinds were rubbery, spotty and inconclusive. For example, while the oceans make up a little more than 70 per cent of the earth’s surface our knowledge of sea-surface temperatures for much of the 20th century depended on where ships sailed, and the measuring of sea-water temperature in leather buckets. The location of land-temperature measurement sites is (unsurprisingly) heavily dependent on where people, and indeed where people in wealthy countries live.
My address made it to the local paper, and I gave a couple of talks on the subject on Robyn Williams’s ‘Ockham’s Razor’ program, plus a few addresses to Rotary, farming and other organisations. At one of them the German science attaché took me aside after the talk and discussion, and almost wagged his forefinger at me. ‘You are a senior figure,’ he said. ‘It is not right for you to say these things. The world is in great danger.’ I replied, as politely as I could, that I was used to reading scientific papers and judging how valuable they were. What I had said was what I thought was the case, after a lot of reading. How much reading in the area had he done? The conversation ended somewhat abruptly. I had come across my first ‘believer’. I was to meet many more, and argued with them too, twice in public.
Five years later I checked to see whether my judgments in 2008 were justified. They seemed to be. This year, the tenth anniversary, is a moment to look more comprehensively at the issue, and that requires two essays, of which this is the first. Two prefatory remarks are needed. The first is that a great deal more scientific work has been done in the past decade on the nature of ‘global warming’ and its running mate ‘climate change’. But quite a lot of it now does not support the central tenets of the climate orthodoxy. The second is that the international and national urgency to address the issue has passed. Governments occasionally talk the talk, but where they can they have stopped walking the walk. The Paris Accord of two years ago is without teeth and is not much referred to any more, except by believers. And these two terms, ‘global warming’ and ‘climate change’, have nowhere near the salience they had ten years ago in the media (for Australian newspapers, for example, see here).
Nonetheless, those who believe that the planet is in great danger are still about, and if anything more worried than they once were, because they can perceive that by and large they do not have the political clout they used to have. Governments are in a bind, because they committed themselves to certain actions a decade or more ago and find it difficult now to get out of them. What we have is a kind of policy impasse. In 2008 I set out what I thought was the central proposition of the global warming issue. It is still the core of the scare.
Human activity in burning coal and oil, and clearing forests has, over the past century, put an enormous amount of carbon dioxide into the atmosphere where it has combined with water vapour and other gases like methane to increase global temperatures in an unprecedented way. The evidence that this has occurred is clear-cut, and the increase in temperature will have, according to our computer models, dire effects on the planet, causing the melting of polar ice, the raising of sea levels, droughts, floods, storms and desertification. We must put an end to this prospect by changing our way of life lest catastrophe strike us. It may already be too late.
I then listed what seemed to me the seven important assumptions built into this scenario. The first was
1. The extent to which the planet is warming
In 2008 it was commonly accepted that the 20th century had seen a rise in average global temperature of 0.6 ± 0.2 degrees Celsius. I pointed out then how imprecise the data were to support such numbers, but was prepared to accept a rough equivalent. One great problem with all this is the considerable warming that occurred in the first half of the 20th century, when the burning of fossil fuels was not as pronounced as it became later in the century. Attention has since been paid to the same metric for the 21st century. One reason is that the steady upward movement in temperature mimicking the rise in CO2 accumulations in the 1980s and 1990s flattened out quickly in the new century, though CO2 accumulations continued to rise steadily. Another was that much more notice is taken of satellite measurements, which only began in 1979, and are almost completely global in their coverage. You can see the trends at page 6 in Ole Humlum’s Climate in 2017 paper, which is based on observations and the data from the five major climate datasets. Yes, temperatures began to rise again in the last three years, but they were accompanied by, if not caused by, the el Nino spike of 2016/7. They have begun to decline since, as the diagram below shows.
What we can say is that the approximately 1.5 degree C rise in temperatures in the last 150 or so years has been irregular. How much of this has been due to greenhouse gas emissions is moot. To this date no one has been able to distinguish the supposed CO2 ‘signal’ from the noise in the climate system, though there have been some efforts (for example, here). The tendency is to try to measure what is thought to be known (volcanic eruptions, ENSO etc), and then suggest that what is left must be caused by greenhouse gas emissions, and therefore by human activity. Such a method implies that all components of natural variability are known and easily measured, which is quite unlikely to be the case.
In any case, the level of warming is not great, and plainly has cyclic aspects. We don’t understand those very well, either.
2. Whether or not this warming is unprecedented
The allegedly ‘unprecedented’ nature of this warming is an important part of the global warming scare. If such warming never happened before, then it must be greenhouse gas emissions that have produced the warming. But what does ‘unprecedented’ mean? We have less than forty years of really good global data, and that’s not nearly enough to say anything much. The rubbery data put together from all sorts of sources for the 20th century, and back to the 1880s (where the evidence is increasingly scant) shows a similar warming in the first half of the century to that in the second half.
The similarity must raise doubts. It is sometimes argued that the first warming period was due to natural variability and the second to greenhouse gas emissions. But, to make the point again, there is as yet no way of isolating greenhouse gas emissions from natural variability. We do know, or at least we can estimate pretty accurately, that there have been a lot more greenhouse gas emissions in the last forty years than there were in the 1900 to 1940 period. But then, if it wasn’t greenhouse gas emissions, what caused the earlier warming period? And can some of the recent warming, or even most of it (a few sceptics would argue, all of it) be attributed to natural variability? If not, why not?
On the face of it, there is nothing at all unprecedented about the warming of the recent past. And it is well to remember that proxy data from ice cores, tree rings, sediments and the like suggest that there were past periods just as warm, or even warmer. The Romans enjoyed one around the time of the birth of Jesus Christ, and the Minoans much earlier enjoyed another, before they were wiped out, probably by a tsunami. Go to the beginning and consider Figure 3 in Ole Humlum’s climate4you.com. The ice-core data come from Greenland. Of these four warm periods (the other is the mediaeval), our present day is much the coolest. OK, Greenland isn’t the world…
[to be continued]