The debate on global warming is over. That is not because the case for greenhouse gases as the cause has been proven or even that the earth is still getting warmer. So much capital, political, scientific and indeed financial, has been invested that there is no turning back. The debate is not going to be reopened. Reports keep appearing making ill supported claims about what has occurred- the number who have already died from global warming, the increase in storms, the increased variability of rainfall and so on- and others, equally ill founded, about what is going to happen. On the other hand, there are no published attempts to consider how greenhouse gas models have performed to date and every obstacle placed in my path when I have tried to get the information to make such a study. Anyone denying the greenhouse gas case – not my position by the way- is ridiculed as a “flat earther,” or dismissed as being in the pay of a vested interest.
The end of debate may well be a good thing since to admit that the case is flimsy would be seized upon and nothing would be done, and the consequences might be disastrous. It is our old friend the producer’s and consumer’s risk; in this case the probability of accepting the greenhouse gas case as true when it isn’t, against the probability of rejecting greenhouse gases as the cause of warming when they are. But those probabilities, even if we knew them, are not the whole story. The cost of not reducing greenhouse gases, if they are the cause of warming, is much greater than the waste of resources resulting from reducing emissions when that is in fact not needed. Unfortunately the costs in both cases are huge, with the first possibility incalculable.
Even if a “good thing”, accepting a case as effectively proven when it isn’t, is something I do not like. It goes against everything I believe in – against evidence, rationality, disinterestedness and objectivity. So I shall continue to look into the business.
Of course if global mean temperatures were to stop rising that would be the end of the matter, although I think we would have to be deep in another ice age before that would be acknowledged.
All I can look at currently are the temperatures and the carbon dioxide levels. Global warming is indicated - one might almost say given- by the daily returns from weather stations. I have criticisms about the way those returns are used to produce a global mean but I doubt my criticisms would affect the estimates significantly. We can accept the results, such as those placed on the web by NASA, as facts. The level of atmospheric carbon dioxide has been measured since 1956 at Manua Loa in Hawaii and the results are also available on the web; the level is said not to vary greatly from place to place so a chain of stations is not necessary.
Global temperature has risen over the 150 or so years for which adequate records are available, but irregularly.  There are many reasons why some years are relatively hot and other relatively cold. The variation depends fundamentally on the laws of physics but played out day-by-day, hour-by-hour, even minute-by-minute, so annual variations from any trend are effectively random; they are also large. If we look at the last 11 years, gas levels have continued their steady rise but temperatures have fluctuated with no clear trend (Fig 1). If we look at the last 7 years the trend is very slightly towards cooler years. However, the fluctuation about the trend is so large that the underlying trend might well be for progressively hotter or progressively cooler years. And 7 years is a short period. Fig 2 shows the trend and the “two Standard Deviation” slopes; there is a 90% chance that the true trend lies somewhere between the extremes. All one can say is that the trend for increasing global mean temperature may have ceased, with the accent very much on “may”. Because carbon dioxide levels have risen steadily the relationship with global mean temperature is almost exactly the same as that with year (Figs 3). If temperature really is no longer rising, though greenhouse gas levels are, it would mean that greenhouse gases are not making the world warmer and almost certainly never were. You will not find all this being pointed out in the Guardian Weekly or at the coming Copenhagen conference – or by the Intergovernmental Panel on Climate Change. To do so would be deemed ‘irresponsible” and perhaps rightly. But if 2009 proves to be on the cool side and 2010 also, my questioning will begin to look rather less irresponsible.
Note.
I have I admit started both series with unusually warm years. That will tend to underestimate any upward trend in temperature just as starting with a very cold year would over estimate.
I have used the standard method of regression analysis. For change with historical time, that is not strictly valid since time increases steadily and inevitably; 2003 follows 2002. Time is not a “variable”. The method is completely valid with carbon dioxide. The analyses give virtually identical results but only because carbon dioxide levels happened to have increased at a uniform rate.

July 2009