Patterns of climate change across Scotland: technical report - Sniffer

study. Since 1961 average spring, summer and winter temperatures have risen by more than
1°C.
• Since 1961 average daily maximum temperatures have been increasing at a faster rate than
average minimum, or night time, temperatures in Scotland. Globally, over approximately the
same period, it is minimum temperatures that have increased at the faster rate. It is interesting
to note that conversely the trend in Scotland over the 1914 to 2004 period also has the
minimum temperatures increasing at the faster rate.
• Scotland has become wetter since 1961, with an average increase of almost sixty percent in
winter months in northern and western Scotland. For the majority of the country there has not
been a large-scale significant change in average summer rainfall although some parts of north
west Scotland have become up to forty five percent drier in summer. Contrary to the Scottish
national trend, Aberdeenshire has seen little change in precipitation in winter months although
this is compensated for in this region by a significant increase in precipitation in autumn
(September-November).
• Heavy rainfall events have increased significantly in winter, particularly in northern and
western regions.
• The snow season has shortened across the country since 1961, with the season starting
later and finishing earlier in the year. The greatest reductions have occurred in northern and
western Scotland.
• Since 1961 there has been more than a twenty-five percent reduction in the number of days
of frost (both air and ground frost) across the country. At the same time, the growing season
length has increased significantly, with the greatest change occurring at the beginning of the
season.
• Inconsistent methods for observing cloud data and the challenges of analysing wind
observations have meant that identification of any trends or patterns of change in these
quantities has not been possible in this study. Further, more complex, data analysis techniques
would be required for such an undertaking.
• The majority of the analysis presented here is based upon data for 1961 to 2004. Longer
data records for temperature and precipitation have allowed trends over this time to be put into
the context of a long period. The study highlights the fact that since 1961 both annual mean
temperature and precipitation have increased at a faster rate than at any other time in the ninety
years considered.
• The trends identified since 1961 are not always consistent with those that might be expected
based upon the future climate of Scotland projected by climate models, although evidence of
such trends often exists in the longer record, i.e. the 1914 to 2004 dataset. This underlines the
fact that caution is required when drawing conclusions about trends and climate change based
upon a relatively short data period.
This study is focused upon the identification of trends in Scottish climate and providing the
regional and spatial detail that national averages mask. The study does not seek to explain, or
attribute a cause, for identified trends. Although some of the trends identified are consistent with
projected future climate for Scotland, it is not possible to say that the trends are evidence of
man-made, i.e. anthropogenic, climate change. However, many of the trends identified are
significant and therefore beyond the range expected from natural variability. Whether or not the
changes are due to anthropogenic climate change it is clear that these observed trends are
often comparable with those predicted for the future. This means that Scotland already has
experience of the impact of such changes and is therefore well placed to plan the necessary
adaptation measures for the future.
Key words: Scotland, climate change, observed trends
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