Atmospheric CO2 has risen 40% sinds 1850. General belief is that this would have stimulated growth of tropical trees, which in turn would have slowed down the rise in CO2. Most models for future climate prediction assume that this effect will also take place in the future. Collaborative research lead by Wageningen University and published in Nature Geoscience shows no evidence for this growth stimulation in the past suggesting that climate models might be overly optimistic in this respect.
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