The Physical Evidence of Earth's Unstoppable 1,500-Year Climate Cycle

Studies | Environment | Global Warming

No. 279
Friday, September 30, 2005
by S. Fred Singer & Dennis T. Avery


Tree Rings

Tree rings can be counted to date events, and their summertime width is wider under good growing conditions (warmth, rainfall) than during poor growing seasons (cold, dry). Tree ring studies are limited by the distance back in time for which researchers can find live trees, dead trees, buried wood or even structural wood from an earlier time which can be accurately dated to its growth period.

A 1,400-year tree ring study in 1990 led by Britain’s Keith Briffa showed little evidence of the Medieval Warming or Little Ice Age.61 In 1992, however, Briffa and several of the same coauthors published another report in Climate Dynamics, noting that “our previously published reconstruction was limited in its ability to represent long-timescale temperature change because of the method used to standardize the original tree-ring data. Here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales.”62 This second report found a cool period from 500 to 700, with 660 an especially cold year. Then it showed generally warm periods from 720 to 1360 (the Medieval Warming) with “peaks of warmth” in the 10th, 11th, 12th and 15th centuries — up to 1430.

In northern Quebec, tree rings and growth sequences from more than 300 spruce tree skeletons buried in a peatland near the tree line showed colder weather from 760 to 860, a warming from 860 to 1000, and severe cold from 1025 to 1400.63

"Tree-growth rings show a 1,500-year pattern in rainfall and temperature."

In Siberia, a continuous 2,200-year temperature record from relict tree rings (rings from trees preserved from an earlier period) shows a warming from 850 to 1150, followed by a sharp cooling from 1200 through 1800, very much in phase with Asia’s climate cycling. The authors report that 20th century warming is “not extraordinary” according to their tree rings.64

On Yakushima Island off southern Japan, carbon-13 isotopes from a giant Japanese cedar infer a temperature 2° C below present from 1600 to 1700, and a warm period about one degree Celsius above present between 800 and 1200.65

In northwestern Pakistan, more than 200,000 tree-ring measurements from 384 trees and more than 20 individual sites show the warmest decades occurred between 800 and 1000, and the coldest periods between 1500 and 1700.66


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