by Renee Hannon, January 7, 2020, in WUWT

Introduction
Ice cores datasets are important tools when reconstructing Earth’s paleoclimate. Antarctic ice core data are routinely used as proxies for past CO₂ concentrations. This is because twenty years ago scientists theorized Greenland ice core CO₂ data was unreliable since CO₂trapped in air bubbles had potentially been altered by in-situ chemical reactions. As a result, Greenland CO₂ datasets are not used in scientific studies to understand Northern and Southern hemispheres interactions and sensitivity of greenhouse gases under various climatic conditions.

This theory was put forward because Greenland CO₂ data were more variable and different than Antarctic CO₂ measurements located in the opposite polar region about 11,000 miles away. This article re-examines Greenland ice cores to see if they do indeed contain useful CO₂ data. The theory of in-situ chemical reactions to explain a surplus and deficit of CO₂, relative to Antarctic data, will be shown to be tenuous. The Greenland CO₂ data demonstrates a response to the Medieval Warm Period, Little Ice Age, Dansgaard-Oeschger and other past climate change events. This response to past climate changes offers an improved explanation for why Greenland and Antarctic CO₂ measurements differ. Further, Greenland CO₂ measurements show rapid increases of 100 ppm during warm events in relatively short periods of time.

Atmospheric CO₂ is More Variable in Northern Latitudes

Figure 1, from NOAA, shows atmospheric CO₂ concentrations measured from the continuous monitoring program at four key baseline stations spanning from the South Pole to Barrow, Alaska. CO₂ has risen from about 330 ppm to over 400 ppm since 1975 and is increasing at approximately 1-2+ ppm/year. Many scientists believe that rapidly increasing CO₂ is mostly due to fossil fuel emissions.