A Handbook of Climate Trends Across Scotland
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© Crown Copyright, Met Office 2006 All rights reserved. No part of this document may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of SNIFFER. The information in this report is provided in good faith and is believed to be correct, but the Met Office can accept no responsibility for any consequential loss or damage arising from any use that is made of it. The views expressed in this document are not necessarily those of SNIFFER. Its members, servants or agents accept no liability whatsoever for any loss or damage arising from the interpolation or use of the information, or reliance upon views contained herein. Dissemination status Unrestricted Research contractor This document was produced by: Claire Barnett and Matthew Perry Met Office, FitzRoy Road, Exeter, Devon, EX1 3PK, United Kingdom; and A handbook of Jo Hossell, Greg Hughes and Chris Procter Woodthorne, Wergs Road Wolverhampton, WV6 8TQ climate trends across Scotland United Kingdom. The report should be referenced as: Presenting changes in the climate across Scotland over the last century Barnett, C., J. Hossell, M. Perry, C. Procter and G. Hughes (2006) A handbook of climate trends across Scotland. SNIFFER project CC03, Scotland & Northern Ireland Forum for Environmental Research, 62pp. SNIFFER’s project manager SNIFFER’s project manager for this contract is: Noranne Ellis, Scottish Natural Heritage SNIFFER’s project steering group members are: June Graham, Scottish Environment Protection Agency (SEPA) Helen McKay, Forestry Commission Peter Singleton, Scottish Environment Protection Agency (SEPA) Guy Winter, Scottish Executive SNIFFER First Floor, Greenside House, 25 Greenside Place, EDINBURGH EH1 3AA Company No: SC149513 Scottish Charity: SCO22375 www.sniffer.org.uk A HANDBOOK OF CLIMATE TRENDS ACROSS SCOTLAND © Crown Copyright, Met Office 2006 All rights reserved. No part of this document may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of SNIFFER. The information in this report is provided in good faith and is believed to be correct, but the Met Office can accept no responsibility for any consequential loss or damage arising from any use that is made of it. The views expressed in this document are not necessarily those of SNIFFER. Its members, servants or agents accept no liability whatsoever for any loss or damage arising from the interpolation or use of the information, or reliance upon views contained herein. Dissemination status Unrestricted Research contractor This document was produced by: Claire Barnett and Matthew Perry Met Office, FitzRoy Road, Exeter, Devon, EX1 3PK, United Kingdom; and A handbook of Jo Hossell, Greg Hughes and Chris Procter Woodthorne, Wergs Road Wolverhampton, WV6 8TQ climate trends across Scotland United Kingdom. The report should be referenced as: Presenting changes in the climate across Scotland over the last century Barnett, C., J. Hossell, M. Perry, C. Procter and G. Hughes (2006) A handbook of climate trends across Scotland. SNIFFER project CC03, Scotland & Northern Ireland Forum for Environmental Research, 62pp. SNIFFER’s project manager SNIFFER’s project manager for this contract is: Noranne Ellis, Scottish Natural Heritage SNIFFER’s project steering group members are: June Graham, Scottish Environment Protection Agency (SEPA) Helen McKay, Forestry Commission Peter Singleton, Scottish Environment Protection Agency (SEPA) Guy Winter, Scottish Executive SNIFFER First Floor, Greenside House, 25 Greenside Place, EDINBURGH EH1 3AA Company No: SC149513 Scottish Charity: SCO22375 www.sniffer.org.uk A HANDBOOK OF CLIMATE TRENDS ACROSS SCOTLAND 1 CONTENTS Introduction 2 Chapter 1 Temperature related variables 6 1.1 Average temperature 7 1.2 24-hour maximum temperature 10 1.3 24-hour minimum temperature 12 1.4 Daily temperature range 14 1.5 Heating degree days 15 1.6 Growing degree days 17 1.7 Length of the growing season 18 1.8 Growing season start and end dates 20 1.9 Extreme temperature range 22 1.10 Length of heat-waves in summer and cold spells in winter 24 1.11 Air frost 26 1.12 Ground frost 28 1.13 Early and late season frosts 30 Chapter 2 Precipitation related variables 32 2.1 Average precipitation totals 33 2.2 Snow cover 36 2.3 Days of heavy rain each year 38 2.4 Number of consecutive dry days 40 2.5 Average rainfall intensity 42 2.6 Maximum five-day precipitation total 44 Chapter 3 Air-pressure related variables 46 3.1 Average air-pressure at sea level 47 3.2 Average wind speed each year 49 3.3 Days of gale each year 50 Chapter 4 Sunshine related variables 51 4.1 Sunshine hours 51 4.2 Cloud cover 54 Appendix 1 Where the information comes from and the techniques we have used to analyse it 55 Analysing the information 57 Appendix 2 References 58 2 Introduction This handbook presents the changes in climate across Scotland in the last century. It provides a benchmark against which we can measure future climate change. This should help with the development of strategies to adapt to the impacts of climate change. The handbook presents the highlights in a simplified way. For a more detailed technical analysis please see the accompanying SNIFFER publication “Patterns of Climate Change across Scotland: Technical Report” at www.sniffer.org.uk. Table 1 presents a summary of the results The Met Office datasets we have used in this showing what we have analysed, and the changes analysis cover temperature and precipitation for Scotland, by region and by timescale (in other from 1914 – 2004, sunshine from 1929 to 2004, words, annual or seasonal). Figure 1 shows the and a range of other variables from 1961 up three regions for which we describe the results. to 2004, including pressure, derived temperature The other sections provide the results of indices, snow cover, wind speed, and the analyses for each of the variable groups (related intensity of rainfall. Appendix 1 provides a brief to temperature, precipitation, atmospheric summary of the techniques we have used. pressure and sunshine and clouds). Figure 1 - Map of Scotland showing boundaries For each group we present the results as: of the three regions as defined in this study • a graph (time series) showing changes each (North, West and East Scotland). year since 1914 or since 1961; • a table summarising average change over the period by each region (see the note below table 2 for a worked example); and • a map of the patterns of change over the period for the whole of Scotland. In presenting the results, we have highlighted changes that are statistically significant at the 5% level. These show that we are 95% confident that we can measure a statistically significant trend in the changes. At the end of each analysis we compare these recent trends with the future climate, as estimated by the UK Climate Impacts Programme Scenarios published in 2002 (UKCIP02). The UKCIP02 scenarios provide a snapshot of future climate for three 30-year periods, the 2020s, 2050s and 2080s. The comparison considers whether or not the trend we have seen already agrees with the future direction of change for that variable and whether the pattern across Scotland is similar or not. When we describe areas of Scotland in this Handbook, a capital letter is used when any of the three regions are being discussed, that is to say ‘North’ Scotland rather than ‘north’ Scotland. A HANDBOOK OF CLIMATE TRENDS ACROSS SCOTLAND 3 Table 1 - Summary of the main findings by variable, region and season and a comparison of the trend for 1961 to 2004 with expectations for the climate in the future as presented by the UKCIP02 scenarios (Hulme et al., 2002). upward trend, downward trend, blank means no trend detectable Variable Change Region Expected future trend by season North East West (from UKCIP02 scenarios) Annual Average Spring Possible increase in all seasons, greater in Temperature Summer south than north. This matches the trends already seen. Autumn Winter Annual 24-hour Spring Maximum temperatures may increase in all maximum Summer seasons. The range of possible increases is temperature smallest in winter and greatest in autumn. Autumn This matches trends we have already seen. Winter Annual 24-hour Spring The minimum temperatures may increase minimum Summer more in winter than summer. This generally temperature matches the trends already seen. Autumn Winter Annual Daily Spring This range may increase most in summer. temperature Summer We cannot find a trend in the information range we have for summer, but some regions Autumn are showing an increasing trend in other Winter seasons. Annual Heating Annual This may reduce in the future, which is in degree days line with the trend already seen, but the possible reduction by the 2080s is 50% to 300% greater than that experienced so far. Growing Annual No estimates have been made in the degree days UKCIP02 scenarios for this measure. Length of the Annual A possible increase in the length of the growing season growing season of 20 to 60 days by the 2080s. We have seen a similar trend but the spatial pattern is different. Growing season Start Estimates for the start of the growing start and end season are similar to those we have already dates End seen, but suggest a later end to the growing season than has been seen already. Extreme Annual No estimates have been made in the temperature UKCIP02 scenarios for this measure. range Length of Summer No estimates have been made in the summer heat UKCIP02 scenarios for this measure. waves and winter Winter cold spells 4 Introduction Table 1 Continued upward trend, downward trend, blank means no trend detectable Variable Change Region Expected future trend by season North East West (from UKCIP02 scenarios) Air frost Spring No estimates have been made in the Summer UKCIP02 scenarios for this measure, but the reductions in minimum temperatures Autumn expected should mean some reduction in Winter the number of air frosts.