What is the climate change debate all about?

In 1981 I was appointed to the Australian Research Grants Committee, the body that advised the Minister for Science on the grants to be awarded to academics across the country that would enable them to carry out the research they wanted to do. It was a highly competitive system, and about 21 of us did the work, covering all disciplines save those in medical science (that was the responsibility of the NH&MRC). People came and went. You had a three -year term that could be extended to five years. Mine was, and I also became the Chairman of the ARGC, was then asked to set up the new body to replace it, the Australian Research Council, and spent three years doing that.

Both in my ARGC and ARC time I got to know, often quite well, other members of these bodies. One was a geologist from James Cook University in Queensland, Bob Carter, who was not only internationally noted for his work but, unlike most scientists, was interested in policy questions. He and I got on well, but we disagreed about matters, too, and that made our relationship memorable. Since he was confident, well-read and outspoken, he was a formidable opponent. We crossed swords most about whether or not the ARGC and ARC should have priorities. I felt that the mood of the times told us that we had to be able to say that some research areas were simply more important to Australia than others. Bob felt that excellence alone should rule.I felt that there was too much supposed excellence about. He felt that meant we needed to do our jobs more skilfully. And so on.

Bob Carter has become one of the most distinguished and able opponents of what I see as the fashionable and quasi-religious notion that the planet is warming and that doom awaits us unless we abandon fossil fuels and all that goes with them — the doctrine of Anthropogenic Global Warming. He has written an major book about it, and speaks from time to time about the issue in Australia and overseas. He has written an excellent summary of what it is that is really in issue in the AGW debate, and the rest of this essay is mostly drawn from that. I should add that while I greatly respect his argument, I think he takes too much notice of temperature data that to me are rubbery. He would reply that unless one uses the data that exist it is hard to have an argument about their meaning.

He argues that there is much more common ground than you would appreciate if your reading and viewing are confined to the mainstream media: climate changes anyway, the earth has warmed, human activity must have contributed to that, and greenhouse gas emissions accumulate. (I would accept all that, too.) What is really at issue are three unknowns: how much net warming will be produced by human activity, whether or not there is any evidence for dangerous warming over the last fifty years, and whether climate models can provide accurate  predictions far into the future.

He then offers to test the DAGW (D=dangerous) hypothesis against what is actually known, like this:

‘(i)     Over the last 16 years, global average temperature, as measured by both thermometers and satellite sensors, has displayed no statistically significant warming; over the same period, atmospheric carbon dioxide has increased by 10%.

Large increases in carbon dioxide have therefore not only failed to produce dangerous warming, but failed to produce any warming at all. Hypothesis fails.

(ii)   During the 20th century, a global warming of between 0.4O C and 0.7O C occurred, at a maximum rate, in the early decades of the century, of about 1.7O C/century. In comparison, our best regional climate records show that over the last 10,000 years natural climate cycling has resulted in temperature highs up to at least 1O C warmer than today, at rates of warming up to  2.5O C/century.

In other words, both the rate and magnitude of 20th century warming falls well within the envelope of natural climate change. Hypothesis fails, twice.

(iii)  If global temperature is controlled primarily by atmospheric carbon dioxide levels, then changes in carbon dioxide should precede parallel changes in temperature.

In fact, the opposite relationship applies at all time scales. Temperature change precedes carbon dioxide change by about 5 months during the annual seasonal cycle, and by about 700-1000 years during ice age climatic cycling. Hypothesis fails.

(iv)  The IPCC’s computer general circulation models, which factor in the effect of increasing carbon dioxide, project that global warming should be occurring at a rate of +2.0O C/century.

In fact, no warming at all has occurred in either the atmosphere or the ocean for more than the last decade. The models are clearly faulty, and allocate too great a warming effect for the extra carbon dioxide (technically, they are said to overestimate the climate sensitivity). Hypothesis fails.

(v)    The same computer models predict that a fingerprint of greenhouse-gas-induced warming will be the creation of an atmospheric hot spot at heights of 8-10 km in equatorial regions, and enhanced warming also near both poles.

Given that we already know that the models are faulty, it shouldn’t surprise us to discover that direct measurements by both weather balloon radiosondes and satellite sensors show the absence of surface warming in Antarctica, and a complete absence of the predicted low latitude atmospheric hot spot. Hypothesis fails, twice.’

Now scientists who actively support the AGW notion will and do take issue with Carter on each of these tests. I would myself say that the fact that warming has stalled over the last 16 years is not conclusive evidence that the AGW notion fails, though the longer the lack of warming persists the weaker the AGW argument must be.

The whole paper that Carter has written is worth reading. I have not even summarised it properly. It is a clear and accessible account of what is still one of the major issues affecting not only our society, but every developed society in the world — in my view to our cost.


Join the discussion 6 Comments

  • hammygar says:

    Denialists place a huge weight on the apparent pause in warming over a very brief period (16 years). Ther’re going to be blown right out of the water when warming resumes in coming years, probably at an unprecedented upward trajectory.

  • Don Aitkin says:


    Setting aside your use of ‘denialists’ (who are they?) as not warranting any response, there is a problem with the ‘apparent’ stasis in warming. If it continues, then indeed there will have to be a very fast warming for the 21st century’s GTA to reach IPCC predictions. And the stasis wasn’t predicted by the models. It wasn’t supposed to happen, which then causes one to wonder how useful the models actually are.

    And it suggests that, even if adding carbon dioxide to the atmosphere does (and must, according to radiative transfer physics) lead to warming, there are plainly other factors out there that counter-balance that warming, part of the so-called ‘natural variability’ that on the whole the IPCC reports play down.

    And that suggests that the science is not settled after all. And that calls into question the supposed urgency of doing things now.

    As you will have seen from my own remarks, I don’t place a huge weight on the stasis. I expect warming to resume at some stage, but many of the indications are that we are in for cooling rather than for warming, and if that is the case, then the great importance of fossil fuels loses even more of its sinister overtones.

  • Malcolm Miller says:

    If only the mainstrem media would know about this, But their journalists only repeat the pr releases of loud special interest groups, like the AGW religion’s supporters.

  • Christine says:

    It would seem useful to answer a number of basic questions in order to put climate science on solid foundations at the macro level:

    1. Is the climate changing? 2. Is it getting warmer or cooler? 3. At what rate is the climate changing (in the short, medium and long term)?

    4. Is the climate changing due to natural factors? 5. Can these be quantified? 6. If so with what degree of accuracy? 7. How does the accuracy of the measurements effect certainty?

    8. Is the climate changing due to human factors? ditto as above (9,10 and 11).

    12. Are there interactions between natural and human factors? ditto as above (13, 14 and 15)

    16. Are these interactions (if they exist) important for our understanding of climate change? 17. How? 18. Why?

    I am assuming that the question of climate status would be positioned somewhere within the short range horizons? Or maybe there have been historical periods of climate status that could give insight into this phenomenon?

    • Don Aitkin says:


      All these questions have been answered, but not everyone agrees (as always). But, quickly, (1, 2 and 3) Relative to 2000 years ago, the world is cooler, relative to a hundred years ago, it is warmer, relative to twenty years ago, it is about the same. Climate includes many other factors than temperature, but we have no records for rainfall, for example, longer than 100 or so years. (4 -11) Yes, natural and human factors are at work, especially when we change landscapes by clearing. Our measurements aren’t very good, and we rely on proxies for anything earlier than 1900. There is no certainty about any of this, and the error bars around proxy measurements are large. (12 to 18) Yes, but we can’t yet separate out the human from the natural, and we don’t know all the natural factors at work.

      ‘Climate status’ puzzles me as a term. We know that there can be long-term periods of drought, and massive floods tend to greatly disturb human settlements, and even end whole societies. Temperature I’ve dealt with. What I feel that I can say with confidence is that we are only at the beginning of our understanding of ‘climate’, though I expect that we will know a great deal more in twenty years.

  • […] at all interested in the topic, and it was not, at least in my memory, much discussed in the ARGC, about which I wrote a couple of days ago. Apparently the Age ran a story in 1986 (I haven’t been able to find it) that sea levels were […]

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