Dozens of rapid warming and cooling periods episodically occurred throughout the last glacial. However, they have often been dismissed as local-only events. A 2020 study published in Science robustly affirms steeper-than-today warming periods spanned both hemispheres and 23 of 25 were “globally synchronous.”
Geologists have long recognized that Greenland abruptly warmed up by 5 to 16°C “within a few decades to centuries” about 25 times in the last ~100,000 years (Capron et al., 2021).
These past abrupt climate changes do not even require a clear external trigger to explain their provenance. They can simply be “unforced or noise-induced oscillations” internal to the climate system (Capron et al., 2021, Li and Born, 2019).
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.
Figure 1. Atmospheric CO2 concentrations from NOAA…
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