Patterns of climate change across
Scotland and Northern Ireland Forum for Environmental Research
(SNIFFER), Scottish Executive, Scottish Environment Protection Agency
(SEPA), Scottish Natural Heritage (SNH) and the Forestry Commission.
Background to research
The Scottish mainland and Scottish Isles warmed by 0.69°C and
0.64°C respectively, over the period 1861-2000 (Jones and
Lister, 2004). Precipitation patterns have also altered, generally
producing drier summer and wetter winters but there has also been an
increased frequency of heavy rain events (Mayes, 1996; Smith, 1995).
Generalised annual values at a national level can mask significant
regional and seasonal variations. In order to plan for adaptation to
climate change there is a need to know the degree of change in specific
locations across the seasons. Only then can potential future
trends for that locality be considered in the context of the latest UK
Climate Impacts Programme (UKCIP) climate change scenarios.
Objectives of research
The aim of this study is to collate records of observed data in order
to provide an up to date assessment of how the climate of Scotland has
changed, not just giving a nationally averaged result but identifying
regional patterns of change. This study provides a benchmark against
which future change can be measured. The analysis of trends shows how
far Scotland’s climate has altered. It also places the
predicted future climate of Scotland within the context of changes
already observed. It thereby provides information essential to those
considering the need to adapt to the impacts of climate change in
Scotland. A stakeholder survey was conducted in order to ensure the
capture of key variables. The findings of the study are presented in
summary form as a Handbook, with the full details of the analysis being
given in this technical handbook.
When descriptions of our changing climate are presented in terms of
nationally averaged annual mean statistics, significant regional and
seasonal variations can be masked. This technical report describes the
analysis of a number of high-resolution datasets. These are based upon
data from a dense network of observing stations that has been gridded
using some of the latest data regression and interpolation techniques.
The datasets include temperature and precipitation from 1914 to 2004,
sunshine from 1929 to 2004, and a range of other variables, such as
mean sea level and snow cover, from 1961. A number of quantities based
upon either temperature or rainfall, such as growing season length and
rainfall intensity, have also been derived. These datasets have been
analysed in order to identify patterns of change in the Scottish
climate over time and space.
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.
- Since 1914 average temperatures in Scotland have risen by
0.5°C. Northern Scotland has warmed at a slower rate than the
rest of the country, with average increases in temperature only being
significant in spring. In northern Scotland, there has been little
change in winter temperatures since 1914.
- Temperatures have increased in every season and in all
parts of Scotland since 1961. This has been the fastest period of
warming observed over the 1914 to 2004 period analysed in this 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
- 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.
Scotland, climate change, observed trends
The report is available for download from the SNIFFER Website
The Technical Report and Handbook are each available separately in
electronic format at £20.00 + VAT
Hard copy available at the following prices:
Technical Report £35.00
A Handbook of Climate trends across Scotland £25.00
All prices less 20% to FWR members.