The problem with climate change is that the topic is genuinely complex, from a scientific point of view. This complexity shows itself in many anomalies. Anomalies are any phenomena which are odd, unusual; they are often unique and deviate from established norms. Climate change science is bursting with anomalies. Scientists, in trying to develop a theory of climate change, have to explain these anomalies.
The only way they can suggest why the anomalies occur is to speculate. They have to abandon their text books (or partly at least) walk out of the laboratory and start guessing at solutions. This is how and why the anomalies of climate change give rise to guesswork or, as scientists call it, speculation.
Now there has to be scientific speculation because out of the speculation comes a scientific hypothesis, which is a possible explanation for an anomaly in climate change science. Once a speculation is chosen as a solution to anomaly the hypothesis must be tested. Usually it is tested by experimentation but you cannot create an experiment the size of the planet and you would not wish to experiment on the planet, even if that were possible. Sometimes a hypothesis can be tested mathematically, but trying to test a climate change hypothesis mathematically does not provide an absolute answer. The algorithms are too complex and the variables are largely unknown.
You can have a good shot at experiments and maths but the result will not be proof or conclusive, but if they are strong enough in favour of your hypothesis, then your hypothesis attains the status of a working hypothesis, which is a provisionally accepted hypothesis, usually provisionally accepted on the basis that it is the most likely one.
I am going to provide just one example of how these stages of scientific opinion might apply to a single phenomenon of climate. Forty years ago, when we had all just emerged from the swinging sixties, it has been now found that the oceans rapidly changed temperature. To top parts of the northern oceans cooled by just under a third of a degree Celsius and the top layers of the southern oceans warmed by about the same amount.
The first stage that the scientists undertook was to guess why this could have happened. Some suggested that aerosols from industrial pollution might be the cause, by reflecting solar radiation back into space in the North, but there being few industries in the south, the effect in the north was great.
Others guessed that this may be related to the increased amounts of fresh water in the northern oceans, perhaps caused by changes in ocean currents. Others say that this rapid change has no scientific effect and that it is just part of a normal cycle of events in the earth’s climate and physical properties.
If we consider just this one phenomena and look at all the different possibilities that could explain it, and then realise that there are literally millions of such anomalies over the period that we can measure the earth’s climate with reasonable accuracy, we can understand why climate science can only provide us with a working hypothesis.
Occam’s Razor argues that the fewer anomalies in any hypothesis the more likely the hypothesis is to be true. I do not dissent from that, provided that we can identify all the anomalies.
The status of the concept of anthropogenic global warming is either a working hypothesis or possibly a theory. A theory can be modelled and the model must account for all the relevant features of the theory and the observations on which the theory was founded. Theories can be disproved, and often are. Theories cannot be proved.
Obviously if the theory is based upon a great deal of information with very few variables it is likely to be right, until new data or information disproves it. If it is likely to be right then we should act upon it. In this sense the theory of anthropogenic climate change (or is it a working hypothesis) is based upon more dated with fewer variables than the theory that climate change is due to other causes than humans.
To measure the quantity and quality of anomalies in each theory will require a more sophisticated tool than the razor or knife that Mr Occam proposed. Mr Sherlock Holmes had another approach; when you rule out the impossible anything left, however improbable, must be the truth. Unfortunately in climate change science having ruled out the impossible you are still left with a body of conflicting improbable and probable matters. In this case the logical way to proceed is to accept the best working hypothesis. That brings humanity as the cause of present climate change, and that is not a bad working hypothesis upon which we should base our actions and policies.