How does rising atmospheric CO2 affect marine organisms?

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Modeling Natural vs. Human-Induced Climate Change
Hulme, M., Barrow, E.M., Arnell, N.W., Harrison, P.A., Johns, T.C. and Downing, T.E.  1999.  Relative impacts of human-induced climate change and natural climate variability.  Nature 397: 688-691.

What was done
Results from recent global climate GCM simulations and two environmental response models were used to analyze the effects of natural climate variability and potential human-induced climate change on river runoff and agricultural wheat yield potential in Europe over the next 50 years.

What was learned
The authors found that the impacts of natural climate variability on runoff and wheat yields were "as great as, or greater than, the estimated impacts of human-induced climate change."

What it means
The authors note that "conventional impact analyses implicitly assume that ... multi-decadal natural climate variability can be ignored."  However, as they showed and concluded in this study, "these assumptions are not correct."  Indeed, the authors convincingly demonstrate that "human-induced climate change may not have as great an impact on natural resources as might multi-decadal natural climate variability."  And if impact is what everyone is concerned about, it would appear that there is little of the human-induced type left to put in the "worry about" category.

Reviewed 15 March 1999