About six years ago Professor Steven Koonin wrote a guest post for Judith Curry's blog site Climate Etc. entitled "Are human influences on the climate really small?" The post was a follow-up to an article Prof. Koonin had written for the Wall Street Journal (WSJ) about six months earlier entitled "Climate science is not settled." The general thrust of these articles was to argue that many effects of man-made climate change were too small to be significant when compared with natural variabilities and climate uncertainties.
Needless to say both articles provoked a heated response from lot of climate scientists and their supporters. One such came from Andrew Lacis. His response was posted on Judith Curry's blog, and then again on Skeptical Science, and it began as follows:
Physicists should take the time to understand their physics better.
Only 1% to 2% . . . that may sound small and insignificant . . . but it isn’t.
It is well known that the normal human body temperature is about 310 K. Furthermore, it is also well known that a seemingly small change (up or down) in absolute body temperature by only 1% (3.1 K, or 5.6 F) would make one sicker than a dog, and, that a 2% change in body temperature (up or down by 6.2 K, or 11.2 F) will virtually guarantee a dead body. From this, it should be sufficiently clear that, when viewed in absolute energy terms, the viable margin between life and death in the Earth’s biosphere is remarkably narrow – so much so that a seemingly insignificant 1% to 2% change in the total energy of the global environment will invariably result in serious disruption of the established infrastructure of life in the biosphere.
The full response from Andrew Lacis ran to over twenty paragraphs and extended to other issues such as changes to atmospheric water vapour concentrations and other climate feedbacks. I am not going to consider the rest of his arguments in detail as they are not pertinent to the main thrust of this post. What I am going to consider is the above quote, minus the rather condescending first line, and ask, is the human body a good analogy for global climate? My considered answer is, no!
The attraction of the above analogy is, I think, two-fold. Firstly, both the normal temperature of the human body (310 K) and the generally assumed mean surface temperature of the Earth (288 K) are fairly similar in magnitude (the difference is only about 7%). Secondly, both the human body and the Earth are highly complex systems regulated by multiple feedback mechanisms, but which at the same time appear to be extremely stable. So, it could be inferred that what is true for one could, or should, be true for the other. In which case, according to the analogy, if a change in body temperature of 1°C in a human is of profound importance to their health and well-being, then the same should be true for the biosphere of the Earth with regard to the interdependence of its own mean temperature and its long-term survival.
Except, that it is not.
Because the mean temperature of the human body does not change by ±10°C or more every twelve hours. Nor does the mean daily temperature of the body change by over 10°C over the course of a month, or in many cases even a week, or by over 50°C from January to July. Nor is there a permanent temperature difference of over 100°C between different points on the body such as the head and the feet. Because if it did do any of this, then a mean temperature rise of only 1°C due to a mild fever would be undetectable. And that is the key point! Yet that is what climate science is trying to measure in respect of a mean global temperature, and then claim that a) the measurement is statistically significant, and b) that the consequences will be so catastrophic that the system will be unable to cope.
You might ask, why should we care now about what a few physicists, climate scientists and commenters wrote over six years ago? The main reason is that those who oppose the Steven Koonin viewpoint, or his right to articulate it, continue to republish quotes like the one above to support their own arguments.
So, thank you to Andrew Lacis for the above analogy. It is indeed a very useful and illuminating analogy.
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