Saturday, October 10, 2009

Climate Hypotheses and the falsification thereof

There is much discussion in climate related circles about this topic being a scientifically based set of events, conclusions and predictions. In scientific circles when new ideas come along they are generally accorded the title of hypotheses and they are then subject to review, with the potential that they will ultimately be discarded because they have been shown to be wrong, or falsified as the technical term would describe it.

Essentially – to use the examples from Wikipedia, if I say that some men are immortal it is not possible to falsify the statement, since I just might not have met one of the immortals yet, but if I say all men are immortal, then production of the first dead body proves the hypothesis wrong.

The question then arises as to how much error a hypothesis is allowed, before it is considered wrong.

For instance I was looking at the Real Climate website, and noted their arguments about the data that they believe falsify Svensmark’s theories on the impact of Galactic Cosmic Rays on global climate. I find this a bit amusing really, since while they are quite happy to argue about falsification when it comes to theories that differ from theirs, they appear remarkably insensitive to seeing the shoe put on the other foot, when it comes to discussions of climate warming. (And incidentally there is some evidence that what Svensmark said is correct. (Which might be why folk, not generally considered to be idiots, are funding him).

RC's previous post, for example discusses the possibility of a pause in the steady progress of global warming that their theories have projected is still going on.

Trends in Global Temperature (from Real Climate – and previously from GISS)

Now the thing is that there is obviously some natural phenomenon going on that would (were greenhouse gases the villain they proclaim) negate the increasing effect of those gases over the past decade. And that has an impact on an earlier study.

It should be remembered that when the whole issue of global warming was first brought to large-scale public attention, one of the arguments made for the influence of greenhouse gases on the climate was that the models of climate behavior without consideration of the influence of greenhouse gases, showed relatively little change over time.

Predicted global temperatures from 13 models run by James Hansen (from Dire Predictions)

You can see that from 1965 the graph set is pretty flat, with all models showing no significant change over the period. Thus, if one accepts that there is something natural that is precluding the global temperature following the theoretical prediction, then one must go back to one of the underlying hypotheses that Dr Hansen proposed - namely that there are no natural phenomena that will likely have any significant effect on global temperatures over the period of time that we are all concerned about. Given that RC is now saying that there are natural causes that are transiently diminishing the effects of carbon dioxide on global temperatures, it would seem that they are concurrently arguing that the initial premise upon which Dr Hansen built his case has now been falsified.

Now when we look at the predictions with greenhouse gas in them then the graphs show that temperatures match those predicted when greenhouse gases are included.

Predicted global temperatures from Hansen’s models (blue), against actual temperatures (red) (from Dire Predictions).

However if one then looks at what Dr Hansen projects from 2000 to 2010 and beyond, one gets a very distinctive upturn in the predicted temperatures:

Dr Hansen’s predicted global temperatures under 3 scenarios (A business as usual; B moderate gas emissions and a volcanic event of significant magnitude; C a volcanic event and reductions in the emission of carbon dioxide by 2000). (Again from Dire Predictions).

Looking at where we are actually at relative to those three scenarios – which have temperature anomalies of A – 1.1 degrees; B – about 1 degree; and C about 0.65 degrees, one can see that the actual temperatures from the top graph are actually closest to following line C at the moment with an increase of somewhere around 0.55 degrees, which is below even the increase that that model predicts, although it does predict a lowering value, suggesting that we have already reached the target for 2012. . However this result, given that carbon dioxide levels have not fallen as predicted, suggests that the model predictions, once outside the range of conditions that prevailed at the time they were written, are not correct. In fact one could conclude that if Dr Hansen’s predictions are summarized into the hypothesis that, without the control of greenhouse gases exemplified by those measures he calls for in scenario C, that global temperatures will increase unacceptably, then this hypothesis has been falsified.

Now Real Climate argues that global temperatures should actually be considered higher, since there is insufficient data from the Arctic, which is considered to be warming much faster than the rest of the globe, and were that considered, then the models and readings would be much closer. . (Interestingly, however, when the ocean temperatures from the North Atlantic are looked at, they now appear to be declining, perhaps falsifying that argument before long).

North Atlantic Heat content (after Tisdale )

The problem with the RC argument is that is that it was the available temperature readings, relative to the model predictions that were touted as being so close in performance (graph 2) during the global warming period of the last part of the last century. Changing the data base as one moves along a line of predictions is generally frowned upon.

There is some growing body of opinion that projects that – just as with curve C above – the global temperature may stabilize around current temperatures for a total of as much as 30-years, before beginning to rise again. That is inconsistent with the predictions of the models used in the above work. Thus it seems only rational to conclude that if there is no discernable increase in temperature, on a consistent basis, in the near future, that the climate change arguments that hang on these graphs for justification must themselves be considered to be falsified.

That would be the scientific conclusion, and were this really a scientific debate then this would be a subject of discussion. Since, however, this has long passed beyond the point where it has become an article of faith with many folk, and the weakness of the foundations on which the Climate Change debate is really built is not to be considered, then one is left wondering how many years of obfustication we must tolerate before the recognition that it is worthy of considerable debate actually occurs.


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