title: Uncertainties and recommendations.
abstract: An assessment of the impacts of changes in climate and UV-B radiation on Arctic terrestrial ecosystems, made within the Arctic Climate Impacts Assessment (ACIA), highlighted the profound implications of projected warming in particular for future ecosystem services, biodiversity and feedbacks to climate. However, although our current understanding of ecological processes and changes driven by climate and UV-B is strong in some geographical areas and in some disciplines, it is weak in others. Even though recently the strength of our predictions has increased dramatically with increased research effort in the Arctic and the introduction of new technologies, our current understanding is still constrained by various uncertainties. The assessment is based on a range of approaches that each have uncertainties, and on data sets that are often far from complete. Uncertainties arise from methodologies and conceptual frameworks, from unpredictable surprises, from lack of validation of models, and from the use of particular scenarios, rather than predictions, of future greenhouse gas emissions and climates. Recommendations to reduce the uncertainties are wide-ranging and relate to all disciplines within the assessment. However, a repeated theme is the critical importance of achieving an adequate spatial and long-term coverage of experiments, observations and monitoring of environmental changes and their impacts throughout the sparsely populated and remote region that is the Arctic.
authors.affiliation: Abisko Scientific Research Station, Sweden. terry.callaghan@ans.kiruna.se
authors.forename: Terry V
authors.initials: TV
authors.lastname: Callaghan
authors.forename: Lars Olof
authors.initials: LO
authors.lastname: Björn
authors.forename: Yuri
authors.initials: Y
authors.lastname: Chernov
authors.forename: Terry
authors.initials: T
authors.lastname: Chapin
authors.forename: Torben R
authors.initials: TR
authors.lastname: Christensen
authors.forename: Brian
authors.initials: B
authors.lastname: Huntley
authors.forename: Rolf A
authors.initials: RA
authors.lastname: Ims
authors.forename: Margareta
authors.initials: M
authors.lastname: Johansson
authors.forename: Dyanna
authors.initials: D
authors.lastname: Jolly
authors.forename: Sven
authors.initials: S
authors.lastname: Jonasson
authors.forename: Nadya
authors.initials: N
authors.lastname: Matveyeva
authors.forename: Nicolai
authors.initials: N
authors.lastname: Panikov
authors.forename: Walter
authors.initials: W
authors.lastname: Oechel
authors.forename: Gus
authors.initials: G
authors.lastname: Shaver
mesh_terms: D000818:Animals; D001110:Arctic Regions; D044822:Biodiversity; D003081:Cold Climate; D003625:Data Collection / Q000379:methods; D017753:Ecosystem; D004784:Environmental Monitoring / Q000379:methods*; D005544:Forecasting / Q000379:methods; D008962:Models, Theoretical; D010944:Plants; D012988:Soil Microbiology; D009626:Terminology as Topic; D014466:Ultraviolet Rays