Simon T. Kaye

With the Copenhagen Summit underway and the low rumble of discontent over the hacked emails debacle still audible, I feel the need to communicate my feelings on all the claims and counter-claims on the ’science’ of global warming.

I marched on the ‘Copenhagen Wave’ last weekend, along with tens of thousands of other people from all around the UK. It’s a worthwhile cause, I’m strongly in favour of firm emissions reduction targets, and I believe that human activity is responsible for the climate change going on around us. Note, however, the use of the word ‘believe’ – I don’t know anything – not scientifically, anyway.

‘Scientific facts’ are curious beasts. Science may be said to be incapable of producing hard-and-fast facts. One formulates a hypothesis; one tests it; if the hypothesis is upheld, and is upheld repeatably, then surely we have a scientific fact on our hands? Well, yes and no.

Within the framework of the experiment, we have shown a ‘fact’ – but it’s possible that laboratory conditions or the specific arrangements of a test differ from what we’d assume to be ‘normal’ conditions. Test conditions are capable of presenting spurious, irrelevant or simply untrue ‘facts’. It works the same way as the framing of verbal logic.

So, scientific facts prove only the specific hypothesis which are tested. More importantly, they can only be assumed to do so temporarily. Facts have use-by dates. The first relevant experiment to come along and throw new light on a question or display slightly different results will once again throw doubt onto any ’scientific fact’, and it is a part of scientific method to assume that proofs are finite in this way. A statement is true until proven false, just as the accused is innocent until proven guilty. The difference is that reasonable doubt runs the other way: if there is reasonable doubt as to the truth of a scientific statement, then it cannot really be called a fact. For this reason, there must be much, much more evidence in support of a claim of scientific fact than there need to be made against it in order to ‘disprove’ it – which is parallel to our legal metaphor, where the onus lies with the prosecution to eradicate reasonable doubt.

The third important point about scientific facts is that, in an important way, they can never get beyond inference. We may observe the correlation between two different things a hundred times in experiments – but all we’ve really seen is the same correlation, a hundred times. So even with the non-existence of contrary evidence, ’scientific fact’ requires someone to look at the evidence and draw a causal conclusion about it all – to claim “these things are not coincidental: one causes the other”.

These three question-marks can help us to look at the human-caused (‘anthropogenic’) global warming argument objectively:

First of all, anyone who tells you that anthropocentric climate change is proven, certain, a done deal, is either lying to you, or doesn’t know much about science. These will be the sort of people who say ‘climate change deniers’ instead of ’skeptics’. Even in so far as there is any such thing as a ’scientific fact’, I cannot in good conscience write that anthropogenic climate change is one – no matter how useful that could be politically.

Why isn’t anthropogenic climate change a scientific fact? First of all, our planet’s atmosphere does not constitute a nice, stable test condition. It has its own ups and downs, is sensitive to the activity of the sun and to its own internal weather patterns, such as el niño. Even today our weather and climate can be altered by unpredictable, freak occurences. Trying to draw a general trend out of this mess, even over fairly long periods, is very hard work. Even worse, climate change scientists will always be frustrated in their efforts to project changes into the future, and a key element of scientific proof is in the success of a model: can we extrapolate our findings into a means to predict what will happen next? In this case, the short-term answer is no.

Instrumental data on warming. The range since useful records began is about 1 degree centigrade in total. From Wikicommons.

Secondly, even with something like an upward trend (which is more or less visible in the data – see the diagram above), there is the problem of cause-attribution. This is made a bigger issue by the fact that the two curves under scrutiny here do not scale particularly well together.

I take as absolutely true that greenhouse gas levels are increasing significantly in the atmosphere, and that these gases are being released because of human activity.

More difficult to prove, but still, in my opinion, true, is the general trend of a warming climate over the last fifty years or so.

But these facts together signify only correlation. I, personally, believe that there is enough evidence to link them causally. This third leap is required for ’scientific fact’. But the problem is that the rate of the increase in temperature does not match in terms of scale the rate of increase of CO2 in the atmosphere, or adhere to the predictions of scientists. There can be little doubt of an increase in CO2 levels – whereas warming levels can be attributed to other causes, such as solar activity or the (thus far barely understood) planetary rhythm of ice-age to warm-patch.

One word of warning  – stick to the instrumental data. Information on the ‘medieval warm period’ is worse than useless, because of course there is no reliable measurement information from that far back. We are limited to the last hundred years or so, and this is both bad news and good news for climate change scientists. It means we must discount the geological probabilities that this planet has been considerably warmer and considerably cooler than it is now at various points in its history, over the course of millions of years.

But these ‘good’ records do show a temperature increase, and it corresponds in terms of timeframe with the start of human industrial activity in earnest. This is enough for me.

Skepticism, it must be noted, is a good thing. It is the scientist’s responsibility to be skeptical, which is why the activities of the UEA scientists is particularly reprehensible. But skeptics must be skeptical always: there is far, far less evidence for ‘alternative’ causes of temperature increase than there is for the greenhouse effect argument, and this is what must be said at the Copenhagen summit.

It is with healthy skepticism that we ought to take action against CO2 emissions. We don’t know anything for certain – but shouldn’t we hedge our bets? I don’t think that scientific rationalism should ever form the basis, by itself, for public policy. But the intuitive response to all this information is to detect a cause, and the response to that intuition is clear.

And wouldn’t it be a noble human objective to cut down on pollution regardless of its relationship with climate-change? Why does no-one ever make that argument?