Spain): Testing high altitude sites sensitivity to millennial scale vegetation and climate variability Maria Leunda (a,b) *, Penélope González-Sampériz (a) , Graciela Gil-Romera (a,c) , Josu Aranbarri (d) , Ana Moreno (a) , Belén Oliva-Urcia (e) , Miguel Sevilla-Callejo (a) and Valero-Garcés, B. (a)