Philip Eden On January Trends
By Paul Homewood
Another interesting column from Philip Eden in last week’s Telegraph.
He makes a couple of points that are worth exploring.
While January temperatures have certainly warmed up since the 18thC, there has been little change since the early 20thC, other than the drop between 1940 and 1970.
This can be seen on the Met Office graph below. (Both minimum and maximum trends follow a similar pattern).
He also comments on the increase in sunshine hours since 1876, largely as a consequence of cleaner air in urban areas, but also seen in rural areas too.
The Met Office data only goes back to 1929, but we can see the trend:
As he points out, wetter winters tend to be warmer, and we can see a similar pattern on the rainfall graph, as on the temperature one above. The early and later years were both wetter and warmer, in contrast to the mid 20th ones.
We would logically expect sunshine hours to have reduced, as the climate has become wetter, yet the opposite is the case. This seems to be strong evidence that cleaner air, even across rural areas, has played a large part in the increase.
The question is – what impact has this factor had on temperatures? It is arguable that the effect is neutral during winter, as the sunshine is not strong enough, or out long enough, to counter the cooling effect of clear skies at night.
For the rest of the year, however, increased sunshine would surely lead to higher temperatures?