Eu va sugerez de asemenea, daca aveti timp, sa studiati si acest articol (si referintele aferente de la final) publicat acum in octombrie 2009 in Science, articol care a declansat un nou val de dezbateri si ridica standardul discutiilor rolului CO2 pe alte coordonate. Concluzia articolului care ia in calcul masuratorile concentratiei de CO2 in ultimii 800.000 de ani si legatura cu variatiile de clima spune ca atunci cind conc. de CO2 (in parti pe milion) era aproape cu valorile pe care le avem noi azi, in acea perioada pe pamint nu exista calota de gheata si nivelul marii era mult mai ridicat (si desigur, nici oamenii nu existau atunci!!). Desi CO2 nu este (singurul) gaz responsabil de incalzirea globala din prezent, totusi are un rol principal in variatiile de clima la nivel global. Nu ar fi o idee buna sa ignoram niste detalii importante.
Daca doriti articolul complet ii puteti scrie direct autorului sau lasati o adresa de e-mail aici si va trimit PDFul.
Coupling of CO2 and Ice Sheet Stability Over Major Climate Transitions of the Last 20 Million Years
Aradhna K. Tripati 1*, Christopher D. Roberts 2, Robert A. Eagle 3
1 Departments of Earth and Space Sciences and Atmospheric and Oceanic Sciences, and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095, USA.; Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK.
2 Department of Earth Sciences, University of Cambridge, Cambridge, CB2 3EQ, UK.
3 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.
* To whom correspondence should be addressed.
Aradhna K. Tripati , E-mail: aradhna.tripati@gmail.com
The CO2 content of the atmosphere has varied cyclically between ~180 and ~280 ppmv over the last 800,000 years, closely coupled with temperature and sea level. For earlier periods in Earth’s history, pCO2 is much less certain and the relationship between pCO2 and climate remains poorly constrained. We use boron/calcium ratios in foraminifera to estimate pCO2 during major climate transitions of the last 20 million years (myr). During the Middle Miocene, when temperatures were ~3 to 6°C warmer and sea level 25 to 40 meters higher than present, pCO2 was similar to modern levels. Decreases in pCO2 were synchronous with major episodes of glacial expansion during the Middle Miocene (~14 to 10 million years ago; Ma) and Late Pliocene (~3.3 to -2.4 Ma).
