February 28, 2007
GCRIO Program Overview
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Global Climate Change Digest
A Guide to Information on Greenhouse Gases and Ozone Depletion
Published July 1988 through June 1999
FROM VOLUME 12, NUMBER 3, MARCH 1999
Growing Season Extended in Europe, A. Menzel and P. Fabian,Nature
397, 659 (1999).
Observations at the International Phenological Gardens indicated that,
since 1959, spring has arrived an average of six days earlier and autumn
has come an average of five days later. The Gardens consist of 77 research
sites across Europe that contain genetically identical clones of various
trees and shrubs. The calculations of the timing of spring and fall were
made from records of the dates on which those trees and shrubs bud and
flower and when their leaves change color and fall off. These changes in
seasonal timing are attributed to the regions temperatures, which
have risen during the past three decades. These observational results
agreed closely with and validated computer models of the effects of rising
temperatures on plant behavior.
Effects of Climatic Variability on the Annual Carbon Sequestration
by a Boreal Aspen Forest, W. J. Chen et al.,Global Change
Biology 5 (1), 41-53 (1999).
To determine variability, CO2 fluxes above an old aspen
forest in Canada were measured in 1994 and again in 1996. Carbon
sequestration was found to be 200 ± 30 g C/m2-y in 1994 and 130 ±
30 g C/m2-y in 1996. The difference was caused by the leaf-emergence dates
being 18 to 24 days earlier in 1994 than in 1996, which exposed the forest
to 16% more solar irradiance in 1994 than in 1996. In addition, the early
growing months in 1994 were 4.8° C warmer than in 1996, increasing
respiration by 20 g C/m2-y.
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