From April 1925 to May 1927 a German expedition took place crossing the Atlantic Ocean from Hamburg (Germany) to the tropic and southern part. At 310 stations he took about 1200 series with about 10 000 samples of sea water ( Spiess 1927, p. 279, 355) analysing most important chemical parameters of sea water as temperature and salinity (9383 samples), oxygen (6577samples) and carbonate content, alkalinity, chlorinity or pH (6549) from the surface down to the ocean grounds. The content of CO 2 from the surface to the ocean floors were also measured and the partial pressure of CO2 over the sea surface (312 samples) were calculated. Wattenberg stated an error of 1-2% accuracy of the CO 2 analysis using the Pettenkofer analyser variant of Krogh modified by Buch and a volumetric Petterson analyser, which he used for most of the measurements and which is known for an accuracy of 2-3%. The values were given as the partial pressure in situ as 10 -4 atm (e.g. 2,7 * 10 -4 atm = 270 ppm = 0,027 Vol%)

A total average for the expedition of 299,6 ppm (corrected: about 298,44 ppm) for the Atlantic Ocean (19N-55S) was calculated. For the year 1926 a total average of 313,4 ppm (corrected: about 311,7 ppm) can be calculated for the latitudes of 9N – 63S. A level of 305 ppm is reconstructed from the ice core records by Neftel et al. The chemical analysis by Wattenberg and the ice core reconstruction result in a difference of 6,7 ppm for 1926 (wet chemical method shows higher level).

These values are well within accuracy (about +-9ppm) of the methods, fit to the levels calculated from the summer data measured by Lundegardh and show the rised CO2 level at the end of the 2nd decade in the 20th century. Strong outgassing with high CO2 levels up to 430 ppm measured over sea around the equator. High CO2 values in the location of the thermohaline circulation with high temperature and pH>8 . pH bandwith the same as today 7,7 -8,3