Present climate and biological change - Climate Change: Biological and Human Aspects - page 196

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1300 1400 1500 1600 1700 1800 1900 2000

Ye a r

SevencenturiesofHoloceneGreenlanddeuterium( 2 H)measurements.Theproportionofdeuteriumintheice,
comparedtothecommonisotopeofhydrogen( 1 H)inwater,isproxyforregionaltemperature(seeChapter2).
Itdemonstratesthehighrapidvariabilityofthisonedimension.Smoothingdatahelps,asdoesincludingmore
thanonedimension.(Bycontrast,Figure5.3isbasedonGreenlandisotopesandsnowaccumulationaswellas
beingsmoothed.)DatafromtheNationalOceanicandAtmosphericAdministration(seeAcknowledgements).

Fig. 5.1

This is not just because of regionality but because different times of the year see
different amounts of water transportation ending up as Greenland ice, so whereas
some parts of the year may be getting warmer, others may be getting cooler, and
what ends up in the ice may not be as representative as researchers would like. Also,
the climate is not one-dimensional. Temperature alone does not determine climate
but a range of factors, such as humidity, precipitation, sunshine, seasonality and
so forth. Instrumentation provides standard, more sensitive, forms of measurements
independent of the constraints of many individual physicochemical, and biological,
palaeoclimatic proxies. There is a somewhat ironic symmetry that we have relied
on proxies, especially biological ones, to determine past climates before the Renais-
sance, and then instrumentation afterwards. The Renaissance enabled there to be an
Industrial Revolution that in turn saw the beginnings of extensive fossil fuel use,
which is now beginning to perturb biological systems. The post-Renaissance period
enabled calibration of the bioproxies used in the pre-Renaissance period. Since the
Renaissance, instrumentation has enabled the discipline of meteorology. Its forecasts
have been useful primarily because the weather affects our biologically based lives
and, more recently, because our anthropogenic (i.e. human-generated) perturbations
of the climate are affecting many biological systems globally. Nonetheless, at first
(in the Little Ice Age) instrumental records were neither as widespread nor as rig-
orously compiled as they became later. Combining early records with a variety of
palaeoclimatic indicators does provide a useful picture, such as that in Figure 5.2.