Snow Cov­er and Cli­mate Change in the Cairngorms Nation­al Park: Sum­mary Assessment

Mike Riv­ing­ton, Mike Spen­cer, Aless­andro Gimona, Rebekka Artz, Douglas War­dell-John­son and Jonath­an Ball. James Hut­ton Insti­tute, Novem­ber 2019

Exec­ut­ive summary

Snow cov­er is a key aspect of the Cairngorms Nation­al Park (CNP). It under­pins the eco­logy, hydro­logy, and eco­nomy. Mod­el­ling snow cov­er based on cli­mate pro­jec­tions is chal­len­ging. This study com­pared his­tor­ic tem­per­at­ure and pre­cip­it­a­tion data (1918−2018) with observed snow cov­er days (1969−2005) to identi­fy how tem­per­at­ure affects snow days. Future snow cov­er days were modeled using UK Met Office data.

Cau­tions in inter­pret­ing future pro­jec­tion results:

1. His­tor­ic­al snow cov­er data is incom­plete, and single loc­a­tions were used for weath­er and snow elev­a­tion analyses.
2. Mod­el­ing of future cli­mate con­sequences on snow cov­er is based on UKCP 18 high emis­sions scen­ario pro­jec­tions (warm­ing of 8.5 W m^-2). More detailed ana­lys­is is needed as fur­ther data­sets are released. Lower cli­mate for­cing RCP scen­ari­os (1.9, 2.6, 4.5, and 6.0) would show lower impacts on snow cover.

Ini­tial res­ults show a reduc­tion in snow cov­er as warm­ing con­tin­ues and accel­er­ates. Suc­cess­ful glob­al emis­sion reduc­tion efforts may mod­er­ate this impact; how­ever, high­er emis­sions rates may increase impacts.

Key find­ings

1. Observed snow cov­er in the CNP (1969−2005) declined, con­sist­ent with trends in oth­er moun­tain areas and the Arc­tic. Some vari­ab­il­ity exists, with sig­ni­fic­ant snow events and a pos­sible increase in the last dec­ade. This declin­ing trend is pro­jec­ted to con­tin­ue and accelerate.
2. A warm­ing trend was observed at CNP met­eor­o­lo­gic­al sta­tions since 1918 for both max­im­um and min­im­um tem­per­at­ures, with vari­ations between months.
   • Octo­ber and Novem­ber show approx­im­ately 1.6°C max­im­um and 0.8°C min­im­um tem­per­at­ure rises, influ­en­cing the like­li­hood of sea­son­al snow cov­er establishment.
   • March, April, and May show a warm­ing trend, indic­at­ing earli­er snow melt.
   • Pre­cip­it­a­tion shows vari­ab­il­ity between years, with no strong trend.
3. A clear decrease in snow cov­er days at all elev­a­tion levels was observed over 35 win­ters (1969÷70−2004÷05), with high­er elev­a­tions show­ing a lar­ger pro­por­tion­al decrease.
4. Near-term estim­ates indic­ate con­tin­ued snow cov­er at the cur­rent range of vari­ation, but with a sub­stan­tial decline from the 2040s, con­sist­ent with UK Met Office and IPCC (2019) res­ults. Some years will have snow com­par­able to the past, but such occa­sions will become few­er. By 2080, some years may have very little or no snow.
5. Snow is com­plex to mod­el and pre­dict, espe­cially in tem­per­ate regions like Scot­land. Future trends are indic­ated, but sub­stan­tial uncer­tain­ties remain.
6. Pro­jec­ted decreases in snow cov­er will have import­ant con­sequences on the eco­logy and hydro­logy of the CNP and sur­round­ing areas, includ­ing biod­iversity, ground­wa­ter, streams and rivers, and flood risk due to rap­id melting.

Con­tents

• Exec­ut­ive summary
• Key find­ings
• Con­tents
• Intro­duc­tion
  • Ana­lys­ing snow cover
  • Pre­vi­ous stud­ies of snow cover
• Ana­lys­is of past trends
  • Tem­per­at­ure and precipitation
  • Snow cov­er days
  • Apprais­al of his­tor­ic­al analysis
• Future pro­jec­tions
  • Tem­per­at­ure
  • Snow mod­el­ling
• Caveats and uncertainties
• Pos­sible implications
• Con­clu­sions
• Next Steps
• Acknow­ledge­ments
• Appendix A: Method
• Appendix B: His­tor­ic­al cli­mat­ic trends and future pro­jec­tions – Balmoral
• Appendix C: His­tor­ic­al cli­mat­ic trends and White­hil­locks snow cov­er and weath­er data comparison
• Ref­er­ences

(The remain­ing con­tent is a detailed ana­lys­is of the points men­tioned above, includ­ing charts and graphs. It is too extens­ive to fully repro­duce here, but the above provides a com­pre­hens­ive summary.)