[permaculture] Early Warning: To Boldly Go Where None Have Been Before...

Lawrence London lfljvenaura at gmail.com
Sat Mar 16 17:48:59 EDT 2013

Early Warning: To Boldly Go Where None Have Been Before...

"The amazing image of the day here is is Figure S3 from the supplementary
material of Marcott et
http://www.sciencemag.org/content/339/6124/1198.full) *A Reconstruction of
Regional and Global Temperature for the Past 11,300 Years,* in the current
issue of Science.  They combined 73 proxy records of temperature from
around the globe - mainly from marine sediments - and used a Monte Carlo
analysis to estimate the uncertainties.  The result is the above picture of
the entire Holocene - the period in which agriculture and civilization have
arisen on this planet for the first time - together with the spike of the
Anthropocene on the right - the period of major human impact on the climate.

Note that the authors' work suggests that global temperature has not yet
exceeded the mid-Holocene optimum, but obviously that is going to change in
a hurry:

Our results indicate that global mean temperature for the decade 2000–2009
has not yet exceeded the warmest temperatures of the early Holocene (5000
to 10,000 yr B.P.). These temperatures are, however, warmer than 82% of the
Holocene distribution as represented by the Standard5×5 stack, or 72% after
making plausible corrections for inherent smoothing of the high frequencies
in the stack (Fig. 3). In contrast, the decadal mean global temperature of
the early 20th century (1900–1909) was cooler than >95% of the Holocene
distribution under both the Standard5×5 and high-frequency corrected
scenarios. Global temperature, therefore, has risen from near the coldest
to the warmest levels of the Holocene within the past century, reversing
the long-term cooling trend that began ~5000 yr B.P. Climate models project
that temperatures are likely to exceed the full distribution of Holocene
warmth by 2100 for all versions of the temperature stack (Fig. 3),
regardless of the greenhouse gas emission scenario considered (excluding
the year 2000 constant composition scenario, which has already been
exceeded). By 2100, global average temperatures will probably be 5 to 12
standard deviations above the Holocene temperature mean for the A1B
scenario based on our Standard5×5 plus high-frequency addition stack."

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