Initial measurements of CO₂ concentrations (1530 to 1940 AD) in air occluded in the GISP 2 Ice Core from central Greenland

Initial measurements of CO 2 in the air of bubbles in the GISP 2 (Greenland Ice Sheet Project 2) ice core were performed using a dry extraction technique and tunable diode laser absorption spectroscopy. The record spans the years 1530 to 1940, and includes part of the little ice age. Absolute dating of the air was obtained from the location of the 14 CO 2 bomb peak in the bubble air, relative dating from the seasonal variations of H 2 18 O and electro‐conductivity. The results for preindustrial times indicate constant atmospheric CO 2 levels of 280±5 ppmv between 1530 and 1810 AD. Thereafter the concentrations rise rather abruptly. The record smoothly connects to the direct atmospheric observations from Mauna Loa.