New paper finds 'much lower risk' to Amazon from climate change

A paper published today in Nature finds "a much lower risk of Amazon forest dieback under CO₂-induced climate change if CO₂ fertilization effects are as large as suggested by current models." The paper adds to other recent papers demonstrating the Amazon is resilient to climate change due to CO2 fertilization, and that Amazon trees will tolerate IPCC projected temperature in the year 2100.

Sensitivity of tropical carbon to climate change constrained by carbon dioxide variability

• Peter M. Cox,
• David Pearson,
• Ben B. Booth,
• Pierre Friedlingstein,
• Chris Huntingford,
• Chris D. Jones
• & Catherine M. Luke

• Affiliations
• Contributions
• Corresponding author

Nature

 

494,

 

341–344

 

(21 February 2013)

 

doi:10.1038/nature11882

Received

 

31 May 2012 

Accepted

 

28 December 2012 

Published online

 

06 February 2013

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The release of carbon from tropical forests may exacerbate future climate change¹, but the magnitude of the effect in climate models remains uncertain². Coupled climate–carbon-cycle models generally agree that carbon storage on land will increase as a result of the simultaneous enhancement of plant photosynthesis and water use efficiency under higher atmospheric CO₂concentrations, but will decrease owing to higher soil and plant respiration rates associated with warming temperatures³. At present, the balance between these effects varies markedly among coupled climate–carbon-cycle models, leading to a range of 330 gigatonnes in the projected change in the amount of carbon stored on tropical land by 2100. Explanations for this large uncertainty include differences in the predicted change in rainfall in Amazonia^4, 5 and variations in the responses of alternative vegetation models to warming⁶. Here we identify an emergent linear relationship, across an ensemble of models⁷, between the sensitivity of tropical land carbon storage to warming and the sensitivity of the annual growth rate of atmospheric CO₂ to tropical temperature anomalies⁸. Combined with contemporary observations of atmospheric CO₂ concentration and tropical temperature, this relationship provides a tight constraint on the sensitivity of tropical land carbon to climate change. We estimate that over tropical land from latitude 30° north to 30° south, warming alone will release 53 ± 17 gigatonnes of carbon per kelvin. Compared with the unconstrained ensemble of climate–carbon-cycle projections, this indicates a much lower risk of Amazon forest dieback under CO₂-induced climate change if CO₂ fertilization effects are as large as suggested by current models⁹. Our study, however, also implies greater certainty that carbon will be lost from tropical land if warming arises from reductions in aerosols¹⁰ or increases in other greenhouse gases¹¹.