Introduction: Is climate research a real science?
I shall certainly admit a system as empirical or scientific only if it is capable of being tested by experience. These considerations suggest that not the verifiability but the falsifiability of a system is to be taken as a criterion of demarcation. In other words: I shall not require of a scientific system that it shall be capable of being singled out, once and for all, in a positive sense: but I shall require that its logical form shall be such that it can be singled out, by means of empirical tests, in a negative sense: it must be possible for an empirical scientific system to be refuted by experience.
Hence the statement, “It will rain or not rain here tomorrow” will not be regarded as empirical, simply because it cannot be refuted; whereas the statement, “It will rain here tomorrow” will be regarded as empirical.
A series of postings under Falsification Tests in Calder’s Updates will compare results for the man-made global warming hypothesis and for Henrik Svensmark’s cosmic climate hypothesis about cosmic rays and clouds.
Although the Svensmark hypothesis is quite recent (1996), it’s a fresh version of a much older and more general solar hypothesis, that the Sun is responsible for climate change over years, decades and centuries. From its origin with William Herschel in 1801, the idea that copious sunspots mean a warm climate and a scarcity means a cooler climate was the leading hypothesis for nearly two centuries.
The solar hypothesis was supposedly falsified in the 1980s when the SolarMax satellite measured the variation in the Sun’s brightness during a solar cycle and found that the changes were too small to be very influential on the climate. That is still the official position of the Intergovernmental Panel on Climate Change (IPCC), but the verdict flew in the face of abundant historical evidence for solar-driven climate change. The Svensmark hypothesis soon provided a mechanism for greatly amplifying the influence of the Sun’s variations.
As for the man-made global warming hypothesis, its adoption by an influential group of climate scientists is also a recent phenomenon. Writing in Scientific Europe (ed. Calder, 1990) the first chairman of the IPCC, Bert BolÍn of Stockholm, recalled that the idea that human beings would alter the Earth’s climate by releasing CO2 was neglected or disbelieved by most climate scientists from 1896, when Svante Arrhenius pointed out the possibility, until 1988, when a meeting of experts in Toronto called for a curb on CO2 emissions.
What changed their minds was mainly the big increase in computer speeds. It enabled the development of ever-more elaborate models to simulate the climate for decades ahead, on various assumptions. The continuing reliance of the man-made global warming hypothesis on the computer models is important to remember. As they assume that positive feedbacks amplify the rather small direct greenhouse effect of CO2, the models easily generate alarming predictions of big temperature rises as CO2 increases.
And they are endlessly adjustable. Medieval astronomers, who believed that all heavenly motions had to be ideal circles, were able to match the imperfectly measured motions of planets by adding epicycles. Similarly, climate scientists can tweak the models to deal with criticisms and would-be Popperian falsifiers keep finding the goalposts moving.
In any case, different models give a wide range of different predictions, both globally and regionally. The man-made global warming hypothesis thus comes perilously close to “It will rain or not rain here tomorrow”, which Popper said is not empirical, because it cannot be refuted. While this slipperiness may be handy for the “warmists” to score temporary debating points, it would leave them with a pseudo-science if there were not some features of the hypothesis that remain open to tests.
Many critics wish to refute the Svensmark hypothesis. Their tests will be evaluated too, starting with claims, much publicized over the past few years, that changes in cloudiness fail to follow sudden changes in the influx of cosmic rays. In such a contentious area I must of course declare an interest, as co-author with Svensmark of The Chilling Stars, which explains his hypothesis.
- Do clouds disappear when cosmic rays get weaker?
- Is the recent warming of Greenland unprecedented?
Other tests of the Svensmark hypothesis will include
- The recently lazy Sun
- Laboratory tests
- The Earth’s changing magnetic field
- Recent changes in the Earth’s cloud cover
- Anomalous Antarctica
Other topics tests of the man-made global warming hypothesis will include
- Do temperature changes follow CO2 ?
- The Hockey Stick
- Climate sensitivity
- Upper air temperatures
- Anomalous Antarctica