Today, an exclusive interview with famed international climatologist Dr Arturo Calor. Dr Calor is leading the scientific fight against man-made global warming.
Thank you for being with us, Dr Calor. Let me ask you this: how do we know the Earth is imperiled, that it’s really growing ever warmer?
Simply because the data shows that the globe is getting hotter. I’ll anticipate your next question and tell you about the data. We have thermometers of various kinds at several locations around the planet. Most of these have been in place a few tens of year, others longer; some have been moved, some have seen cities grow up around them, others have seen cities die. Some locations are new, some old. The thermometers measure the temperature at various heights, but usually near the surface. There is some error in this process, and incompatibilities, but we can down weight these difficulties because the subject is so important.
Because the instrumental record is so brief, we also infer temperatures using proxies.
These are things like widths of tree rings, ratios of isotopes of certain chemicals in other living things and ice, and so forth. What we do is match the proxies with known temperatures measured by thermometer, and then build a statistical model which estimates a parameter. We report that parameter as the error-free estimate of the temperature.
Wouldn’t it be better to remove these parameters—“integrate them out,” in statistical parlance—and report on the uncertainty of the actual predicted temperature, which will always be much higher than the uncertainty of the parameter?
No. Because then we would be less certain than we now are. Plus, we are very busy people and that sort of thing takes a lot of time.
I see. Very compelling. What’s the next step?
We take all of the measurements and estimates, process them through a filter which attempts to remove the largest mistakes, and then we average what’s left over together. We call this average the Global Average Temperature. This average, we now know, has been increasing. It has gone up by a little over a half degree centigrade since the beginning of the industrial revolution.
Do we know the plus and minus of this estimate?
I don’t follow you.
Well, all these different locations and ways of measuring temperature and all the models that predict but do not directly measure temperature. Surely there is some uncertainty in that half degree estimate.
Ah, I see. It is the duty of science to seek certainty, to dispel the dark clouds of ignorance. It would be of no use to concentrate on uncertainty. Many professionals are working on this problem, therefore we are very sure of the results.
I see what you mean. Can you tell us about satellites?
Ah, there we have something. Satellites have been measuring temperatures for a few decades now, and these also show that temperatures are going up (well, sometimes going up).
But satellites don’t directly measure temperature. Isn’t it so that they measure radiation and through a physical-statistical algorithm estimate temperature?
This is natural, yes.
This implies that there is uncertainty in that estimate: another plus and minus. Do you account for that in your estimates?
These satellites are calibrated by very complicated computers, a very expensive process. We are confident in the data they produce.
Taken in all, we are as sure as we are about anything that the temperature has increased a few tenths of a degree and that most of this increase is due to the activity of mankind.
How do we know that?
We build very beautiful, extraordinarily complex computer models which prove this. Although they are difficult to fully comprehend, at base they are very simple.
We know that carbon dioxide captures heat in the lower reaches of the atmosphere. The more CO2 there is, the more heat captured. We also know that a doubling of pre-industrial levels of CO2 will only raise the temperature an insignificant amount. Yes?
So we build into these models a feedback mechanism that says as more CO2 is added, the temperature increases non-linearly. We then run these models and we find exactly what we expected to see: increasing CO2 leads to a positive feedback in temperature!
But aren’t you just seeing what you put into the model? It’s not quite an independent verification of the theory.
You forget that we also have evidence that these models have produced simulations that look, after some processing, like actual observations. That should be enough proof that our theory is correct.
Perhaps. But aren’t there literally hundreds of knobs and dials that you need to tweak to “tune” the models so that they first produce those simulations? Do you have independent evidence that these models predicted new data better than predictions based on the assumption that your theory is wrong?
Look here, young man. I hope you are not going to take the denialist position. If we don’t do something now, by the time we confirm everything, it may be too late.
You can’t argue with that. Thank you for talking to us, Dr Calor.
My pleasure. I hope this interview increases the chance that my grant is funded.