2094] reported a precision of ±3 ppm for measurements of CO2 made by the chemical method.
In contrast using the Infra-Red Gas measurements of CO2.
nalyser (IRG ), they found a precision of ±1 ppm for
While precision quantifies the measurement-to-measurement repeatability, a serious con- cern for any measurement is the question of ‘accuracy’. Do all the measurements exhibit a systematic bias, such that the (average) measured value differs from the true value of what is meant to be measured?
Many measurements actually involve comparison of a sample to a standard.
the accuracy of such a measurement is tied to the accuracy of the standard.
Thus when Bischof
method. ( veraging multiple chemical measurements of the standard will overcome the inher- ently lower precision of the chemical method). Thus Bischof’s agreement between chemical and IRG measurements could be essentially guaranteed. However in producing standards for
program, Bischof’s group used an independent approach bases manometric
niques — mixing gases from precisely calibrated volumes (described in the same issue of
as Bischof’s paper).
Bischof’s ability to merge results from the two techniques represents a val-
Keeling’s results from Mauna Loa — both indicating about 315 ppm. standards using manometric techniques.
Keeling also prepared his
Heaven and Earth has five sections on temperatures in historical times headed: The Roman Warming (250 BC – 450 D) pages 59 to 60 and citing references 213 to 222.
The Dark 223 to 238.
D – 900
D) – a period of cooling – pages 61 to 63, citing references
The Medieval warming (900 – 1300 D) pages 63 to 72 citing references 239 to 295. The Little Ice ge (1280 – 1850 D) pages 72 to 86 citing references 296 to 367. The late twentieth century warming (1850 – present) pages 86 to 87 citing references 368 to 369. These sections are followed by a cross-cutting review, The long tale of the lone pine, (pages 87 to 99 and citing references 370 to 400) primarily addressing the ‘hockey-stick’ controversy.
While specific misrepresentation are noted in the point-by-point analysis, this section ad- dresses whether the body of evidence presented in Heaven and Earth supports the claims of large globally-coherent temperature swings with extended periods much warmer than the present.
These first four periods (denoted RW, D , MWP and LI ) are alleged to be globally syn- chronous periods of alternating warm-cold-warm-cold times, but a significant fraction of the evidence contradicts this. Contradictory examples cited by Plimer are:
for Quebec ‘severe cold from 1025 to 1400 representing the Little Ice
ge’ (p70 citing
For Sierra Nevada ’dense forests grew above the current tree line during the Roman