date: Mon Nov  6 10:03:16 2000
from: Tim Osborn <t.osborn@uea.ac.uk>
subject: Fwd: intense precip
to: hilles@easynet.co.uk

> I am very concerned by the strong correlations between UK Winter Rainfall
>and solar activity and the failure of the authorities to incorporate such
>data in their forward planning - we appear to be paying a bitter price for
>this here in Gloucestershire. 
>  
> Your rainfall data had been previously been published to illustrate
>increasing UK rainfall due to Greenhouse Gas emission led Global Warming -
>there would appear to be a strong solar component to this also.
>  
> By failing to acknowledge this and incorporate this in our plans we are
>also failing to produce a cohesive argument for Sustainable Development -
>certainly as far as the petrol protesters are concerned!

Dear Julian,

Mike Hulme asked me to reply to your email (copied above).  The possible link between solar variability and winter precipitation intensity is very interesting - one of the scientific reviewers of our paper in fact asked us to add some comments about it to our original scientific paper.  We declined to do so, however, mainly because we had a second record that covered the period from 1931-1997, though based on only 63 weather stations rather than 120 stations used to create the figure that appeared in the media.  The second record showed a very similar trend to our main results over 1961-1995, and also showed the 11-year variability that indicates a link to solar activity over this period.  *But* over the 1931-1960 period it showed no link at all to solar activity.  It is quite possible that the 11-year oscillations over 1961-1995 are purely coincidental, and that the solar-climate link is weak or non-existent.

The range of scientific opinion is quite broad on the topic of how much climate variability and change is driven by solar variations.  Nevertheless, as more observational data and improved statistical analysis techniques become available, it is becoming increasingly obvious that solar variations are important.  For temperature, many scientists now feel that natural solar variations were the main contributor to the early 20th century warming that occurred between about 1910 and 1950.  The dramatic warming since 1980, however, cannot be explained by changes in solar output.  So, the role of solar variability is starting to be acknowledged, though it cannot explain all changes, and is much more uncertain than the greenhouse effect (in terms of quantifying past changes and in understanding physical/chemical mechanisms that can amplify a small change in radiation into a large climate response).  It also does not imply that the greenhouse effect is necessarily weaker than is currently believed, so the best way to think of it might not be that climate change scenarios due to increasing concentrations of greenhouse gases are wrong, but just that the level of natural variability that should be superimposed upon them is larger if solar variability is included.  This is, of course, my personal opinion.

Best regards

Tim