Tuesday, December 18, 2012

Another day, another non-hockey-stick

A paper published today in Quaternary Research reconstructs June-July air temperature over the past 785 years in British Columbia, Canada. The paper shows that reconstructed temperatures at the end of the record in 2010 were colder than in the 1940's and during at least 6 other periods within the Little Ice Age from 1350-1850 AD. The temperature record shows there is nothing unusual, unnatural, unprecedented, or accelerated about the 20th and 21st centuries.
Top graph shows reconstructed temperatures from 1225-2010. The reconstructed temperatures of 2010 have been exceeded many times over the past 785 years, even during the Little Ice Age

Tree-ring derived Little Ice Age temperature trends from the central British Columbia Coast Mountains, Canada

  • University of Victoria Tree-Ring Laboratory, Department of Geography, University of Victoria, Victoria, British Columbia, Canada V8W 3R4


Most glaciers in the British Columbia Coast Mountains reached their maximum Holocene extent during the Little Ice Age. Early- and late-Little Ice Age intervals of expansion and retreat fluctuations describe a mass-balance response to changing climates. Although existing dendroclimatic records provide insights into these climatic fluctuations over the last 400 yr, their short durations prohibit evaluation of early-Little Ice Age climate variability. To extend the duration of these records, submerged coarse woody debris salvaged from a high-elevation lake was cross-dated to living chronologies. The resulting chronology provides the opportunity to reconstruct a regional June–July air-temperature anomaly record extending from AD 1225 to 2010. The reconstruction shows that the intervals AD 1350–1420, 1475–1550, 1625–1700 and 1830–1940 characterized distinct periods of below-average June–July temperature followed by periods of above-average temperature. Our reconstruction provides the first annually resolved insights into high-elevation climates spanning the Little Ice Age in this region and indicates that Little Ice Age moraine stabilization corresponds to persistent intervals of warmer-than-average temperatures. We conclude that coarse woody debris submerged in high-elevation lakes has considerable potential for developing lengthy proxy climate records, and we recommend that researchers focus attention on this largely ignored paleoclimatic archive.

No comments:

Post a Comment