A team of mostly northern European researchers led by Professor Dr. Jan Esper, department of geography, Johannes Gutenberg University, Mainz, Germany, have used tree-ring density measurements from living and subfossil northern Scandinavian pines in Finnish Lapland to produce a climate reconstruction reaching back to 138 B.C.

The research findings, published in the July 8 Nature Climate Change journal, assert the tree ring data allowed the researchers ?EUR??,,????'?????<

The researchers believe their findings prove the world was much warmer than previously thought, and that the earth has been slowly cooling for 2,000 years at a rate of 0.3???????(R)?C (3.74???????(R)?F) per millennium.

The annual growth of tree rings, said the researchers, is the most important witnesses over the past 1,000 to 2,000 years to how warm and cool past climate conditions were.

Esper says this cooling rate may not seem that significant, ?EUR??,,????'?????<

He adds: ?EUR??,,????'?????<

The 2000 years of cooling, according to the researchers, is the result of ?EUR??,,????'?????<

?EUR??,,????'?????<

The researchers came from Johannes Gutenberg University (Germany), Swiss Federal Research Institute, Oeschger Centre for Climate Change Research, University of Bern, Finnish Forest Research Institute, Institute for Coastal Research (Germany), School of Geography and Geosciences, University of St Andrews, Scotland, Department of Geography, Climatology, Climate Dynamics and Climate Change, Justus-Liebig University (Germany) and the Max Planck Institute for Meteorology in Hamburg.

Ref: Esper J, Frank D, Timonen M, et al. Orbital forcing of tree-ring data. Nature Climate Change, 08 July 2012.

Click here to read the study.