Developing site scale projections of climate change in the Scottish Highlands

Abstract

With recent warming trends projected to amplify over the coming century, there are concerns surrounding the impacts on mountain regions. Despite these concerns, global (GCMs) and regional climate models (RCMs) fail to capture local scale-dependent controls on upland climates. A modelling framework combining climate model outputs and station data is presented and used to explore possible future changes to temperature with altitude in the Scottish Highlands. The approach was extended by modelling shifts in seasonal isotherm values associated with existing vegetation zones. To achieve this, temperature lapse rate models (LRMs) were applied to 1961-1990 baseline (BL) observed station data for selected stations in the eastern Highlands using seasonally representative lapse rate values (LRVs) derived from paired station values. Tests against 3 upland station records ranging from 663 to 1245 m indicated a credible model performance for the mean seasonal maximum (T max ) and minimum (T min ) BL values evaluated. Following derivation of seasonal isotherm values for the present upper limit of vegetation zones via the LRMs, selected scenario data outputs from the corresponding Hadley Centre RCM (HadRM3H) 50 × 50 km grid cells were used to project future changes to BL values via the LRMs. The findings suggest substantial shifts in the isotherm associated with each zone for the scenarios selected, with shifts in T min more marked than those for T max , although substantial uncertainties remain. Following an exploration of the results for the region, we suggest that a refinement to the approach linked to a wider modelling effort incorporating other important controlling variables for upland species could inform future management initiatives for mountain areas more generally.

Altitudinal temperature lapse rates in an Alpine valley: trends and the influence of season and weather patterns

“…Potential sub-seasonal controls such as snow cover did not show a major influence on vertical distribution of temperature. In future investigations, wind, air humidity and cloud cover data should be included as done by Milionis and Davies (2008) and as suggested by Coll et al (2010).…”

Climate change and the British Uplands: evidence for decision-making

“…Direct observations of recent climate (Burt & Holden 2010, Coll et al 2010) suggest upland areas are already experiencing change, and that this change is greater than in lowland systems. Burt & Holden (2010) found that over the period 1961-2000 upland weather stations showed a rise in mean temperature that was stronger in winter than in summer, with minimum temperature rising more than maximum temperature, whereas in the lowlands the changes were similar between minima and maxima.…”

“…Higher run off at high elevations in winter when bare peat is loosened by freeze-thaw activity may increase POC loss, although this effect could be countered by warmer conditions. Differences between upland and lowland weather stations observed by Burt & Holden (2010) and Coll et al (2010) suggest lowland data cannot be used to infer change in the Uplands (Malby et al 2007). In the UK, only 4% of temperature stations that have ever been operational are located above 300 m and yet around onethird of the UK's land surface is higher than 300 m. Spatial heterogeneity between upland weather stations is also significant due to topography, the effects of regional circulation patterns, and feedbacks related to snow and ice cover in zones with seasonal mean temperature close to 0°C (Manley 1952, Burt & Holden 2010.…”

“…Seasonal and spatial climate heterogeneity due to scaledependent local controls is not fully captured in the present generation of Global Climate Models (GCMs) and Regional Climate Models (RCMs) due to the relatively course resolution of model grids. Coll et al (2010) propose a methodology of combining information from weather station data on the gradients of temperature change between upland and lowland areas (lapse rate) with RCM outputs, to capture the scale of change more likely to be experienced in upland environments.…”

“…Funding priority was given to work that used climate projections to identify areas most at risk of change, and the implications of this change for peat formation and persistence , Clark et al 2010b,c,d, this Special, Gallego-Sala et al 2010. Ongoing work by network partners also included in this Special gives a broad picture of upland peat condition (Billett et al 2010); drivers of change-including burning (Yallop et al 2010), gully erosion (Evans & Lindsay 2010, this Special) and climate change (Burt & Holden 2010, Coll et al 2010; model studies of change due to different drivers (Heinemeyer et al 2010, Smart et al 2010, Smith et al 2010a; implications of climate change for upland birds (Pearce-Higgins 2010, this Special) and wildfire (Albertson et al 2010, this Special); and application of the ecosystem services approach to uplands (Maltby 2010, Cornell 2010. In this introduction, we bring together the evidence presented and evaluate the implications for managing upland ecosystem services under a changing climate.…”