How does rising atmospheric CO2 affect marine organisms?

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Eurasian River Flows
MacDonald, G.M., Kremenetski, K.V., Smith, L.C. and Hidalgo, H.G. 2007. Recent Eurasian river discharge to the Arctic Ocean in the context of longer-term dendrohydrological records. Journal of Geophysical Research 112: 10.1029/2006JG000333.

In introducing their study, the authors write that "sustained increases of river discharge from northern Eurasia into the Arctic Ocean basin could be a key diagnostic of global climate warming," since climate models suggest that the planet's strongest response to greenhouse gas forcing should occur in high northern latitudes, where concomitant increases in precipitation could be expected to significantly increase river flows.

What was done
MacDonald et al. first demonstrate that "discharge variability of the largest northern Eurasian rivers is correlated with broad geographic-scale variations in aridity as captured by the Palmer Drought Severity Index," which "is a synthetic hydrometeorological index incorporating precipitation, evaporation and soil moisture storage that is often highly correlated with tree ring width variations and river discharge," after which they "use tree ring records from a network of sites extending across northern Eurasia to provide reconstructions [extending back to AD 1800] of annual discharge for the October to September water year for the major Eurasian rivers entering the Arctic Ocean (S. Dvina, Pechora, Ob', Yenisey, Lena, and Kolyma)."

What was learned
The four researchers report that the increased annual discharges of the mid to late 20th century that have been previously reported "are not significantly greater than discharges experienced at other times of higher flow over the preceding 200 years, and are thus still within the range of long-term natural variability." In addition, they say their "longer-term discharge records do not indicate a consistent positive significant correlation between discharge [and] Siberian temperature." In fact, they report there are actually weak negative correlations between discharge and temperature on some of the rivers over the period of their study.

What it means
Even in the Arctic, it would appear we are still waiting for the hydrological response the authors describe as "a key diagnostic of global climate warming" to manifest itself.

Reviewed 24 September 2008