Megafossil Carbon Dating Indicates Sweden Was 2-3°C Warmer Than Today During The Last Glacial

“Modern warming is within natural Holocene climate variability” – Kullman and Öberg, 2024

From about 16,800 to 6000 years ago warmth-dependent tree species grew 300-700 altitudinal meters higher than they do today on Mt. Åreskutanthan, Swedish Scandes.

Due to the well-known warmth threshold for boreal tree species and the lapse rate (0.6°C per 100 m), recovering birch, spruce, and pine megafossil remains at much higher elevations than today’s treeline altitudes affirms much warmer-than-today climates during the late last glacial and through the early Holocene, when CO2 ranged from 190 to 255 ppm.

“It is increasingly evident that common boreal tree species grew close to this summit in a climate, 2-3°C warmer than at present, during the Lateglacial and early Holocene periods 16 800- 6000 years ago.”

The scientists point out that such early dating for warmer-than-today climates has been viewed as controversial, as it is assumed the Earth had not sufficiently warmed or deglaciated until about 11,000 years ago, near the official starting timeline for the Holocene. But the carbon-dating of tree megafossils is regarded as a much more reliable data collection method than pollen analysis and terrestrial cosmogenic nuclide analysis, so these results are robust.

“Moreover, Mt. Åreskutan has been in the centre of a controversy concerning the date of deglaciation and late-glacial arboreal performance. Kullman (2000, 2002) presented robust megafossil data, showing unequivocal presence of mountain birch (Betula pubescens ssp. czerepanovii), spruce (Picea abies) and pine (Pinus sylvestris), as early as about 16 000 cal. a BP, close to the summit 300-400 m higher than present-day treelines.”

While there has been warming in this region recently, the warming is “within natural Holocene climate variability” and poses no threat to these landscapes. Instead, warming may enhance biodiversity in this region.

The Intergovernmental Panel on Climate Change (IPCC) promulgates a contrasting “alarmist and dystopic” viewpoint of warming as a “serious and imminent threat to man and planet Earth” as they simultaneously “downgrade natural climate history and rely more on immature and unvalidated numerical models.”

Image Source: Kullman and Öberg, 2024

For good measure, another new Scandinavian study (Salonen et al., 2024) indicates today’s temperatures in northern Finland are among the coldest of the last 8000 years (see “Present-day value” dashed line). Much of the Holocene – as well nearly all of the last interglacial (LIG) – was 2 to 2.5°C warmer than present.

Image Source: Salonen et al., 2024