Rings in fossilised pine trees have proven that the world was much warmer than previously thought - and the earth has been slowly COOLING for 2,000 years.Update: Here is the link to the article at Nature. It indicates:
Measurements stretching back to 138BC prove that the Earth is slowly cooling due to changes in the distance between the Earth and the sun.
The finding may force scientists to rethink current theories of the impact of global warming.
It is the first time that researchers have been able to accurately measure trends in global temperature over the last two millennia.
Over that time, the world has been getting cooler - and previous estimates, used as the basis for current climate science, are wrong.
Their findings demonstrate that this trend involves a cooling of -0.3°C per millennium due to gradual changes to the position of the sun and an increase in the distance between the Earth and the sun.
‘This figure we calculated may not seem particularly significant,’ says Esper, ‘however, it is also not negligible when compared to global warming, which up to now has been less than 1°C.
'Our results suggest that the large-scale climate reconstruction shown by the Intergovernmental Panel on Climate Change (IPCC) likely underestimate this long-term cooling trend over the past few millennia.’
The finding was based on semi-fossilised tree rings found in Finnish lapland.
Professor Dr. Jan Esper's group at the Institute of Geography at JGU used tree-ring density measurements from sub-fossil pine trees originating from Finnish Lapland to produce a reconstruction reaching back to 138 BC.
In so doing, the researchers have been able for the first time to precisely demonstrate that the long-term trend over the past two millennia has been towards climatic cooling.
‘We found that previous estimates of historical temperatures during the Roman era and the Middle Ages were too low,’ says Esper. ‘Such findings are also significant with regard to climate policy, as they will influence the way today's climate changes are seen in context of historical warm periods.’
Solar insolation changes, resulting from long-term oscillations of orbital configurations, are an important driver of Holocene climate. The forcing is substantial over the past 2,000 years, up to four times as large as the 1.6 W m−2 net anthropogenic forcing since 1750, but the trend varies considerably over time, space and with season. Using numerous high-latitude proxy records, slow orbital changes have recently been shown to gradually force boreal summer temperature cooling over the common era. Here, we present new evidence based on maximum latewood density data from northern Scandinavia, indicating that this cooling trend was stronger (−0.31 °C per 1,000 years, ±0.03 °C) than previously reported, and demonstrate that this signature is missing in published tree-ring proxy records. The long-term trend now revealed in maximum latewood density data is in line with coupled general circulation models, indicating albedo-driven feedback mechanisms and substantial summer cooling over the past two millennia in northern boreal and Arctic latitudes. These findings, together with the missing orbital signature in published dendrochronological records, suggest that large-scale near-surface air-temperature reconstructions relying on tree-ring data may underestimate pre-instrumental temperatures including warmth during Medieval and Roman times.(Notes omitted).