Trace gas data include; Net Ecosystem Production (NEP), Ecosystem Respiration (ER) and methane emissions measured in fertilized, warmed and control plots in 3 tundra types at Toolik Lake, from 1991 to 1993; soil respiration measured in treatment plots in moist acidic and non-acidic tundra in 2000; NEP and ER, plus soil temperature, soil moisture and vegetation descriptions for the ITEX flux survey plots 2003 – 2006. ITEX data include measurements made at Toolik Lake and Imnavait Creek, at Abisko in northern Sweden, in Adventdalen, Svalbard and in Zackenberg valley, northeast Greenland.