How does rising atmospheric CO2 affect marine organisms?

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Qilian Mountains, Tibetan Plateau, China
Liu, X., Shao, X., Zhao, L., Qin, D., Chen, T. and Ren, J. 2007. Dendroclimatic temperature record derived from tree-ring width and stable carbon isotope chronologies in the Middle Qilian Mountains, China. Arctic, Antarctic, and Alpine Research 39: 651-657.

Based on ring-width and δ13C data derived from long-lived Qilian juniper trees in the middle Qilian Mountains of China (37-39N, ~99-103E), Liu et al. (2007) reconstructed a 1000-year temperature history of the region that captures approximately 75% of the temperature variance over the calibration period of 1960-2000 and correlates extremely well with a well-established Northern Hemisphere temperature reconstruction. The six researchers say the two warmest intervals of their new temperature history are 1060-1150 and 1900-2000, with peaks occurring around 1100 and 1999; and in viewing the graph of their results, the peak temperatures of these two times look identical. However, the new temperature history does not extend as far back in time as the hemispheric temperature history, which rises to its highest level prior to the time that Liu et al.'s history begins. As a result, Liu et al. conclude that their temperature reconstruction "has not included all of the Medieval Warm Period and, perhaps, not even its warmest period [our italics]." All we can report, therefore, is that the MWP of this study encompasses AD 1060-1150, and that the MWP = CWP at least, although the earlier portion of the MWP was probably warmer than the CWP at this location.