How does rising atmospheric CO2 affect marine organisms?

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A Christmas Island El Niņo History
Woodroffe, C.D., Beech, M.R. and Gagan, M.K.  2003.  Mid-late Holocene El Niņo variability in the equatorial Pacific from coral microatolls.  Geophysical Research Letters 30: 10.1029/2002GL 015868.

What was done
The authors used oxygen isotope ratios obtained from Porites microatolls at Christmas Island in the central Pacific to provide high-resolution proxy records of ENSO variability since 3.8 thousand years ago (ka).  In doing so, they note that "Christmas Island is particularly well-placed [2°00'N, 157°30'W] to capture a large proportion of the El Niņo-La Niņa SST [sea surface temperature] variation, and represents an optimum site for monitoring ENSO (Evans et al., 1998)."

What was learned
In the words of the authors, "individual ENSO events in the late Holocene [3.8-2.8 ka] appear at least as intense as those experienced in the past two decades."

What it means
Contrary to the oft-repeated climate-alarmist claim that global warming will lead to more frequent and intense ENSO events, as suggested by the modeling work of Timmermann et al. (1999), the authors find no support for this hypothesis in their Christmas Island data.  In addition, they note that "geoarcheological evidence from South America (Sandweiss et al., 1996), Ecuadorian varved lake sediments (Rodbell et al., 1999), and corals from Papua New Guinea (Tudhope et al., 2001) indicate that ENSO events were considerably weaker or absent between 8.8 and 5.8 ka," which was the warmest part of the Holocene.  Indeed, they report that "faunal remains from archeological sites in Peru (Sandweiss et al., 2001) indicate that the onset of modern, rapid ENSO recurrence intervals was achieved only after ~4-3 ka," or during the long cold interlude that preceded the Roman Warm Period (McDermott et al., 2001).

Evans, M.N., Kaplan, A. and Cane, M.A.  1998.  Optimal sites for coral-based reconstruction of global sea surface temperature.  Paleoceanography 13: 502-516.

McDermott, F., Mattey, D.P. and Hawkesworth, C.  2001.  Centennial-scale Holocene climate variability revealed by a high-resolution speleothem ð18O record from SW Ierland.  Science 294: 1328-1331.

Rodbell, D.T., Seltzer, G.O., Abbott, M.B., Enfield, D.B. and Newman, J.H.  1999.  An 15,000-year record of El Niņo-driven alluviation in southwestern Ecuador.  Science 283: 515-520.

Sandweiss, D.H., Richardson III, J.B., Reitz, E.J., Rollins, H.B. and Maasch, K.A.  1996.  Geoarchaeological evidence from Peru for a 5000 years BP onset of El Niņo.  Science 273: 1531-1533.

Sandweiss, D.H., Maasch, K.A., Burger, R.L., Richardson III, J.B., Rollins, H.B. and Clement, A.  2001.  Variation in Holocene El Niņo frequencies: Climate records and cultural consequences in ancient Peru.  Geology 29: 603-606.

Timmermann, A., Oberhuber, J., Bacher, A., Esch, M., Latif, M. and Roeckner, E.  1999.  Increased El Niņo frequency in a climate model forced by future greenhouse warming.  Nature 398: 694-696.

Tudhope, A.W., Chilcott, C.P., McCuloch, M.T., Cook, E.R., Chappell, J., Ellam, R.M., Lea, D.W., Lough, J.M. and Shimmield, G.B.  2001.  Variability in the El Niņo-Southern Oscillation through a glacial-interglacial cycle.  Science 291: 1511-1517.

Reviewed 27 August 2003