Basert på målinger i 616 borehull verden over av avviket mellom forventet
geotermisk gradient og faktisk temperaturkurve ned gjennom hullene
konkluderer noen forskere med en global temperaturstigning de siste fem
hundre år med 1 grad (hvorav det meste de siste hundre), hvilket er mer
enn atmosfæriske målinger/estimater har vist.
Borehullsmålinger gir mer nøyaktige svar enn de mer usikre atmosfæriske
målingene, idet bakken lagrer tidligere temperaturer helt eksakt.
Karsten Johansen
Nature 403, 756 - 758 (2000) © Macmillan Publishers Ltd.
Temperature trends over the past five centuries reconstructed from borehole
temperatures
SHAOPENG HUANG, HENRY N. POLLACK & PO-YU SHEN
For an accurate assessment of the relative roles of natural variability and
anthropogenic influence in the Earth's climate, reconstructions of past
temperatures from the pre-industrial as well as the industrial period are
essential. But instrumental records are typically available for no more than
the past 150 years. Therefore reconstructions of pre-industrial climate rely
principally on traditional climate proxy records, each with particular
strengths and limitations in representing climatic variability. Subsurface
temperatures comprise an independent archive of past surface temperature
changes that is complementary to both the instrumental record and the
climate proxies. Here we use present-day temperatures in 616 boreholes from
all continents except Antarctica to reconstruct century-long trends in
temperatures over the past 500 years at global, hemispheric and continental
scales. The results confirm the unusual warming of the twentieth century
revealed by the instrumental record, but suggest that the cumulative change
over the past five centuries amounts to about 1 K, exceeding recent
estimates from conventional climate proxies. The strength of temperature
reconstructions from boreholes lies in the detection of long-term trends,
complementary to conventional climate proxies, but to obtain a complete
picture of past warming, the differences between the approaches need to be
investigated in detail.
This archive was generated by hypermail 2b29 : Thu Aug 03 2000 - 10:25:55 MET DST