By Paul Homewood
The sharp rise in UK temperatures, which effectively began in the 1980’s, is widely known about, but, (and I may be wrong here), has never been satisfactorily explained. Indeed, I am not sure anybody from the Met Office, Hadley Centre, etc has ever seriously attempted to explain it.
Usually, whenever it is mentioned, it is brushed aside as “climate change”. I have always thought this to be nonsense, as, whatever our views of global warming theory, CO2 does not possess the magical properties that enable it to suddenly raise temperatures in such a way, thereafter followed by a decade long pause. Theory tells us that, as CO2 increases in the atmosphere, temperatures should rise gradually and steadily.
A few weeks ago, whilst checking something else, I became aware that around the same time that UK temperatures began to rise, sunshine hours also increased sharply, as the Met Office below shows. Indeed, not only did it rise, but it increased to levels well above anything seen since records start in 1929.
I naturally wondered whether there was a connection here, but was initially thrown as the largest increase in sunshine hours was during winter and spring, with little change in summer. This seemed counterintuitive, since we would normally associate bright, sunny winters with cold weather. At that stage, I filed it all away in my memory and went off to beat the wife instead.
However, in last week’s Sunday Telegraph, I came across this piece on December climate from Philip Eden, (as always, not available on line).
Now the jigsaw began to fit into place. The increase in sunshine hours, particularly during winter, was not caused by changing weather patterns but a reduction in air pollution. It is not unreasonable, then, to surmise that this increase in sunshine was, at least in part, responsible for the increase in temperatures we have seen.
As the graph below shows, there is pretty good correlation between sunshine and temperature.
There is nothing very new in this argument, as air pollution has often been quoted as the reason for the decline in northern hemisphere temperatures during the 1960’s and 70’s. However, that logic misses the point that pollution has been a major factor since the mid 19thC. If it is true that a polluted atmosphere can depress temperatures, then these temperatures have been lower as a result for a century or more.
With a cleaner atmosphere now, temperatures have simply returned to the level they would have been at in the past.
This phenomenon of a sharp rise in late 20thC temperatures is not limited to Britain. We see the same effect across much of NW Europe, for instance France and Germany, as GISS show:
Combined with the recovery of the Atlantic Multidecadal Oscillation, from its low point in the late 1970’s, how much has reduced air pollution, and therefore more sunshine, contributed to UK and European warming in the late 20thC?