The Canadian Arctic’s surface temperatures have been up to 15 to 25°C warmer than today during the geologically recent Holocene, Pleistocene, and Pliocene epochs.
Scientists (Campbell-Heaton et al., 2021) assessing the ratio of winter temperature at the ground surface to that in the air (the “freezing n-factor”) suggest ground surface winter temperatures now (1981-2016) average -33°C in the Canadian Arctic’s Eureka Sound Lowlands.
About 9000 to 10,000 years ago, ground surface temperatures reached -18°C at this location, which is 15°C warmer than present. Winter air temperatures, were, on average, “6-8°C warmer than today” at this time too.
Image Source: Campbell-Heaton et al., 2021
Other sites in this same region of the Canadian Arctic (Eureka, ~78°N) were 22-25°C warmer than today during the Pliocene (Fletcher et al., 2017), or 3-4 million years ago (Ma).
Mean annual temperatures (MAT) for the neighboring Meighen Island, for example, were about 4°C during this period, which is approximately 2°C warmer than the current MAT in Anchorage, Alaska (2°C). Today’s MAT at this location is around -20°C.
Image Source: Fletcher et al., 2017
Image Source: Rybczynski et al., 2013
It was during the Pleistocene that the Greenland ice sheet – which is today covered in 2 to 3 kilometers of ice (height) – was so warm it periodically melted to the ground, meaning the ice “disappeared on several occasions” (Young et al., 2021).
Image Source: Young et al., 2021
The peak CO2 values during the Pleistocene are alleged to be 280 ppm, which is lower than it was during the latter stages of the recent Little Ice Age period (~290 ppm).
These temperature reconstructions thus strongly suggests CO2 concentrations have little or nothing to do with mean annual surface temperatures in Arctic regions.