by K. Richard, Jan 3, 2025 in NoTricksZone
Today, with CO2 levels supposedly in the “dangerously high” range, Central Greenland has 3 kilometers of ice piled atop it.
Scientists have known since the GISP2 borehole was drilled in 1993 that Central Greenland deglaciated at least once in the late Pleistocene (Bierman et al., 2024). Indeed, the Summit of the modern Greenland ice sheet was actually ice-free at some point between 250,000 and 1.1 million years ago – which is relatively recent from a geological perspective.
Plants, wood, insects, fungi and other remnants suggestive of vegetation were recovered from the bottom of the boring site. This is quite a contrast to today’s 3000-meters-high ice sheet at this same location.
“The presence of poppy, spike-moss, fungal sclerotia, woody tissue, and insect parts in the GISP2 till shows that tundra vegetation once covered central Greenland, mandating that the island was largely ice-free.”
The atmospheric CO2 concentration is presumed to have ranged between 275 and 290 ppm during the Late Pleistocene, or during this same period when Greenland was ice-free. These sub-300 ppm CO2 levels are thought to be the same as they were from 1700 to 1900 (the Little Ice Age), when, as today, Central Greenland has remained buried in kilometers of ice.
The authors of this study use existing knowledge of Greenland’s climate (for example, Summit’s mean July temperature is -7°C) to calculate how much warmer Central Greenland was “when the ice was gone” during the last 1.1 million years. Controlling for lapse rate, Central Greenland’s average surface air temperatures were likely +3 to 7°C in July when it had no ice sheet.
The atmospheric CO2 concentration thus appears to be largely unrelated to either Greenland’s climate or its state of glaciation.
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