Open Research Online The Open University’s repository of research publications and other research outputs Local scale assessment of climate change and its impacts in the Highlands and Islands of Scotland Thesis How to cite: Coll, John (2007). Local scale assessment of climate change and its impacts in the Highlands and Islands of Scotland. PhD thesis The Open University. For guidance on citations see FAQs. c 2007 John Coll https://creativecommons.org/licenses/by-nc-nd/4.0/ Version: Version of Record Link(s) to article on publisher’s website: http://dx.doi.org/doi:10.21954/ou.ro.0000fa2d Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyright owners. For more information on Open Research Online’s data policy on reuse of materials please consult the policies page. oro.open.ac.uk Open University - UHI Millennium Institute ‘Local scale assessment of climate change and its impacts in the Highlands and Islands of Scotland ’3 By John Coll A thesis submitted to the Department of Earth Sciences of the Open University, in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) December 2006 UHI Millennium Institute Environmental Research Institute, The Open University The North Highland College, Milton Keynes, UHI Millennium Institute, MK7 6 AA, UK Thurso KWH 7JD, Scotland © This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with the author and that no quotation from the dissertation, nor any information derived therefrom, may be published without the author’s prior, written consent. v v >-o<5fr A J o i ProQuest Number: 13889976 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a com plete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest ProQuest 13889976 Published by ProQuest LLC(2019). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States C ode Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 Abstract Abstract The global climate is warming and there is consensus that recent warming trends will amplify, as the present century progresses, in response to a continued build up of atmospheric greenhouse gas (GHG) concentrations. However, there are limitations associated with Global Climate Model (GCM) and Regional Climate Model (RCM) outputs for topographically diverse regions. Strategic management decisions relating to maritime upland communities require locally resolved projections of change across a range of elevations, which are not supplied by the present generation of models. Here, some of these challenges are addressed via a series of distinctive analyses. Quality controlled baseline station data are used to assess performance outputs for seasonal mean values of temperature and precipitation from an RCM at representative locations across the region. In the case of temperature these inter-comparisons indicate a warm bias in the RCM-simulated seasonal minima for the transition seasons of spring and autumn, whereas for summer maxima there is a cold bias in RCM- simulated values. RCM-generated outputs of future changes to temperature and precipitation are then variably combined with station data to model altitudinal changes at western and eastern upland locations. These analyses indicate a substantial upward migration in key seasonal temperature isotherms associated with present vegetation zones for the climate change scenarios used. This approach is then extended by applying selected outputs to conduct Climate Change Impact Assessments (CCIAs) for the scenarios used in a series of upland case studies. The analyses flag a number of remaining research challenges. Principally, these are that scale-dependent controls on local topo-climates are not adequately captured in the GCM driven RCM projection. While the approach delivers more refined local-scale projections of possible change across a range of elevations than has hitherto been available, residual uncertainties associated with the use of GCM/RCM outputs remain. Table of Contents Glossary 1. Introduction....................................................................... 1 1.1 A Wider Context for Regional Climate Change Assessment......................... 1 1.1.1 Drivers of recent global and hemispheric trends.. .................................. 1 1.1.2 Sources of variability in the climate system ............................................ 2 1.1.3 Detection and attribution of recent changes ............................................ 4 1.1.4 Projected future changes at global and hemispheric scales ....................... 9 1.2 Hemispheric and Regional Influences on NW European Climate ............... 12 1.2.1 North Atlantic climate stability - the role of the Atlantic thermohaline (THC) circulation........................................................................................... 12 1.2.2 The influence of the North Atlantic Oscillation (NAO) ...... ..................... 17 1.3 Context and Background to The Altitudinal Modelling of Temperature ............................................................................................................. 20 1.3.1 A global context............................................... 20 1.3.2 Maritime upland sensitivity to climate change .......................................... 22 1.3.3 Altitudinal zonation of vegetation in the Highlands ................. ................ 25 1.3.4 The influence of oceanicity on vegetation zones ......................... 26 1.3.5 Species and habitat factors influencing migration in response to warming.......................................................................................................... 28 1.4 Uncertainty in Regional Climate Change Scenarios ........................................ 31 1.4.1 GCM and scenario limitations.................................................................. 31 1.4.2 Sources of uncertainty in the UKCIP02 scenario ................................... 35 1.5 Objectives 40 Table of Contents 2. Methods: Construction Of A Baseline Climatology For The Highland Region................................................................ 42 2.1 Creating A Temperature Station Network .......................................................... 42 2.1.1 Obtaining the raw data and determining a baseline period .................... 42 2.1.2 Deriving the annual means ........................................................................ 45 2.1.3 Deriving the seasonal means ..................................................................... 45 2.1.4 Adding existing data to the station network ........................................... 47 2.2 Creating A Precipitation Station Network........................................................... 49 2.2.1 Obtaining the raw data .............................................................................. 49 2.2.2 Deriving the annual totals .......................................................................... 49 2.2.3 Deriving the seasonal totals ....................................................................... 50 2.3 Variability in Observed Temperature and Precipitation Data Time-Series................................................................................................................ 52 2.4 Working With The HadRM3 Model Outputs And Baseline Data .................. 54 2.4.1 Obtaining the UKCIP02 data outputs from HadRM3 ............................ 54 2.4.2 Extracting the data for ‘Highland’ grid-boxes ........................................ 55 2.4.3 Spatially referencing stations to the HadRM3 grid cells ....................... 58 2.4.4 Inter-comparison: Station Observed 1961-90 Baseline Averages and HadRM3 Simulated 1961-90 Averages ................................................... 59 2.4.4.1 Temperature: Method I Inter-comparison. ...................................... 59 2.4.4.2 Temperature: Method II Inter-comparison ............................................. 61 2.4.4.3 Precipitation: Method I Inter-comparison .............................................. 63 2.4.4.4 Precipitation: Method II Inter-comparison ............................................. 63 2.4.4.5 Precipitation: Method III Inter-comparison ............................................ 64 2.5 Lapse Rate Models (LRMs) for The Projection of Future Temperature Changes ........................................................................................................... 2.5.1 Obtaining upland station temperature records for validating the lapse rate models. .............................................................................................. 66 Table of Contents 2.5.2 Constructing and testing the lapse rate models against the 1960-1990 baselines (observed and HadRM3 simulated) ......................................... 66 2.5.3 Perturbing the baseline model outputs with selected future scenario outputs fromHadRM3 ............................................................................... 69 2.5.4 Utilising the lapse rate models to infer future shifts in key seasonal isotherms.....................................................................................................