Upper-bound estimate of past atmospheric CO mixing ratios for the Northern Hemisphere high latitudes spanning from 1700 to 2018 CE. This multisite composite CO baseline spanning 1700–1957 CE was generated by considering the D4, NEEM, NGRIP, and PLACE CO records.
Drillings: NEEM, PLACE, D4, NGRIPDrilling locations: NEEM : LATITUDE: 77.45 N, LONGITUDE: 51.06 W; PLACE : LATITUDE: 72.58 N, LONGITUDE: 37.64 W; D4 : LATITUDE: 71.40 N, LONGITUDE: 43.08 W; NGRIP : LATITUDE: 75.10 N, LONGITUDE: 42.32 WDrilling years: NEEM : 2009 and 2011; PLACE : 2015; D4 : 2001; NGRIP : 2000Analytical methodology: Continous Flow Analysis (CFA) coupled with laser spectroscopy detection (OF-CEAS)Laboratory of analysis: Desert Research Institute (DRI, USA)Analysis dates: NEEM : 2011 and 2013 * PLACE 2015 * D4 : 2013 * NGRIP : 2013