Cloud heights are always reported as height above ground level (AGL), not above sea level. For example, if ATIS says "scattered clouds at 2,000 feet," it means 2,000 feet above the ground at that aerodrome.

At an aerodrome at sea level (like Amsterdam or Dublin), 2,000 feet AGL is 2,000 feet altitude. At an aerodrome at 4,000 feet elevation (like Innsbruck or St. Moritz), 2,000 feet AGL means 6,000 feet altitude above sea level.

This is a critical distinction. Always remember: cloud bases in ATIS are AGL.