It appears that in Greenland at least, the current warming cannot be said to be “unprecedented”, since similar magnitudes and rates of warming are present in several previous eras. Man certainly didn’t cause those warming periods, so natural climate change obviously had a significant effect on Greenland temperatures over the past 4000 years.
In a paper entitled “High variability of Greenland surface temperature over the past 4000 years estimated from trapped air in an ice core” the authors state:
… we reconstruct Greenland surface snow temperature variability over the past 4000 years at the GISP2 site (near the Summit of the Greenland ice sheet; hereafter referred to as Greenland temperature) with a new method that utilises argon and nitrogen isotopic ratios from occluded air bubbles. The estimated average Greenland snow temperature over the past 4000 years was −30.7°C with a standard deviation of 1.0°C and exhibited a long-term decrease of roughly 1.5°C, which is consistent with earlier studies. The current decadal average surface temperature (2001–2010) at the GISP2 site is −29.9°C. The record indicates that warmer temperatures were the norm in the earlier part of the past 4000 years, including century-long intervals nearly 1°C warmer than the present decade (2001–2010). Therefore, we conclude that the current decadal mean temperature in Greenland has not exceeded the envelope of natural variability over the past 4000 years, a period that seems to include part of the Holocene Thermal Maximum.
However, in order to get it past the pal-review system, the following caveat was inserted to appease the headbangers:
Notwithstanding this conclusion, climate models project that if anthropogenic greenhouse gas emissions continue, the Greenland temperature would exceed the natural variability of the past 4000 years sometime before the year 2100.
Unfortunately, it does little to dampen the effect of the preceding paragraph. Namely even with the additional CO2 presently in the atmosphere and its accepted small warming effect, Greenland was still warmer in the past.
Abstract is here.
(h/t Climate Depot and C3 Headlines)
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