A new peer reviewed study based on an analysis of megafossil tree remains documents the indisputable conclusion: it was warmer during both the Roman and Medieval periods - ergo, extreme climate change can happen without human involvement.
The above plots (click each plot to enlarge) of ancient tree lines from previous research provides ample evidence that indeed climates were warmer prior to human CO2 emissions. This new research examines 455 radiocarbon-dated mega-fossils from Scandinavian region.
This newest study establishes the following:
- that "fundamental aspects of glacial, Lateglacial and early Holocene plant cover and landscapes in northern Scandinavia
- that mega-fossil analysis is the only methodology that can "accurately document the existence of a certain tree species at a certain spot and at a certain point of time in the past."
- indicates that "summer temperatures during the early Holocene thermal optimum may have been 2.3°C higher than present,"
- that "the pine tree line was about 100 m higher than today (i.e., early 21st century) c. 1940 and 1300-930 cal. years BP," while noting that "the same applies to birch by c. 1700 and 1300 cal years BP," which clusters "represent the Medieval and Roman times."
- that "these temperature anomalies were succeeded by a distinct tree line/temperature dip, broadly corresponding to the Little Ice Age."
- that "the emergence during the past two millennia of at least two short-term tree line and thermal excursions to higher than present levels (i.e. early 21st century) indicates that the current performance of the ecological and climatic systems is well within the envelope of the natural variability
- that "the pine tree line (and summer temperature) was consistently higher than present ... during the Roman and Medieval periods, c. 1900 and 1000 cal years BP."
Note: Doing a search of the internet did not result in finding a definition for 'megafossil' yet a definition for 'microfossil' was readily available. For purposes of this posting, megafossil refers to fossilized material that can be viewed with the naked eye.