How does rising atmospheric CO2 affect marine organisms?

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Previous Interglacial Sea Surface Temperatures Off the Western Coast of North America
Reference
Herbert, T.D., Schuffert, J.D., Andreasen, D., Heusser, L., Lyle, M., Mix, A., Ravelo, A.C., Stott, L.D. and Herguera, J.C. 2001. Collapse of the California Current during glacial maxima linked to climate change on land. Science 293: 71-76.

What was done
Proxy sea surface temperatures (SSTs) were analyzed over the past 550,000 years from several marine sediment cores obtained along the western coast of North America from around latitude 22N at the southern tip of the Baja Peninsula to around latitude 42N off the coast of Oregon.

What was learned
Tucked away in this paper is an important finding relative to today's debate on global climate change. According to the SST data analyzed by the authors, "the previous interglacial (isotope stage 5e) produced surface waters several degrees warmer than today," such that "waters as warm as those now at Santa Barbara occurred along the Oregon margin." Furthermore, it can readily be seen from the SST histories presented in figure 2 of the paper that SSTs for this region in the current interglacial have not reached the warm peaks witnessed in all four of the preceding interglacial periods, falling short by a margin of 1 to 4C.

What it means
No one would argue against the conclusion that the warmer SSTs observed along the California margin in each of the four previous interglacial periods were the result of natural climate change. This study thus provides an excellent benchmark for evaluating any contemporary SST trend against natural climate variability. It would take, for example, a warming on the order of 4C before natural climate change could be discounted as the sole cause of the warming. Furthermore, given the degree of SST warmth in this region during the past four interglacials, we should not be surprised to see SSTs there naturally rise substantially above their uncharacteristically cold present-day values.