A More accurate History of Climate-Without Tree Rings
In 2008, a minor correction was issued:
A climatic reconstruction published in E&E (Loehle, 2007) is here corrected for various
errors and data issues, with little change in the results. Standard errors and 95%
confidence intervals are added. The Medieval Warming Period (MWP) was significantly
warmer than the bimillennial average during most of the period 820 – 1040 AD. The
Little Ice Age was significantly cooler than the average during most of 1440 – 1740
AD. The warmest tridecade of the MWP was warmer than the most recent tridecade, but
not significantly so.
Historical data provide a baseline for judging how anomalous recent temperature changes
are and for assessing the degree to which organisms are likely to be adversely affected
by current or future warming. Climate histories are commonly reconstructed from a
variety of sources, including ice cores, tree rings, and sediment. Tree-ring data,
being the most abundant for recent centuries, tend to dominate reconstructions. There
are reasons to believe that tree ring data may not properly capture long-term climate
changes. In this study, eighteen 2000-year-long series were obtained that were not
based on tree ring data. Data in each series were smoothed with a 30-year running
mean. All data were then converted to anomalies by subtracting the mean of each series
from that series. The overall mean series was then computed by simple averaging.
The mean time series shows quite coherent structure. The mean series shows the Medieval
Warm Period (MWP) and Little Ice Age (LIA) quite clearly, with the MWP being approximately
0.3°C warmer than 20th century values at these eighteen sites.
The below is from:
Energy & Environment · Vol. 18, No. 7+8, 2007, A 2000-YEAR GLOBAL TEMPERATURE RECONSTRUCTION
BASED ON NON-TREERING PROXIES, Craig Loehle, Ph.D.
Energy & Environment · Vol. 19, No. 1, 2008, CORRECTION TO: A 2000-YEAR GLOBAL TEMPERATURE
RECONSTRUCTION BASED ON NON-TREE RING PROXIES, Craig Loehle, Ph.D.