From Hockey Shtick (via C3) we find reports of a new Peer-reviewed study to add to the collection.
A paper published last week in the journal Climate of the Past examines the climate of central China over the past 1800 years using two different types of proxies. The paper finds higher temperatures and precipitation were present during the Medieval Warming Period (960-1100 AD) than at the end of the 20th century. This study also shows both the rate and magnitude of the rise in temperature from the year ~ 700- 880 AD were much greater than over a comparable period including the 20th century.
In regards to the infamous Michael Mann and IPCC 'hockey-stick' chart, it was claimed that past climate temperatures could be ascertained by tree ring growth. Subsequently, it was determined that Mann had ignored other important factors in tree ring growth, including: water availability, atmospheric CO2 levels, atmospheric nitrogen levels, parasites, and sunlight.Now, scientists have discovered a much more important influence than temperatures on tree ring growth: animal (domestic or wild) behavior, especially chewing on the trees. If browsing on the trees has a great impact, then the animals' dung may be another influence that goes unaccounted for.