Positive feedback between global warming and atmospheric CO2 concentration inferred from past climate change

There is good evidence that higher global temperatures will promote a rise of greenhouse gas levels, implying a positive feedback which will increase the effect of anthropogenic emissions on global temperatures. However, the magnitude of this effect predicted by the available models remains highly uncertain, due to the accumulation of uncertainties in the processes thought to be involved. Here we present an alternative way of estimating the magnitude of the feedback effect based on reconstructed past changes. Linking this information with the mid‐range Intergovernmental Panel on Climate Change estimation of the greenhouse gas effect on temperature we suggest that the feedback of global temperature on atmospheric CO2 will promote warming by an extra 15–78% on a century‐scale. This estimate may be conservative as we did not account for synergistic effects of likely temperature moderated increase in other greenhouse gases. Our semi‐empirical approach independently supports process based simulations suggesting that feedback may cause a considerable boost in warming.

[1]  R. Schnur,et al.  Climate-carbon cycle feedback analysis: Results from the C , 2006 .

[2]  K. Holmgren,et al.  Highly variable Northern Hemisphere temperatures reconstructed from low- and high-resolution proxy data , 2005, Nature.

[3]  Leonard A. Smith,et al.  Uncertainty in predictions of the climate response to rising levels of greenhouse gases , 2005, Nature.

[4]  T. Stocker,et al.  Supporting evidence from the EPICA Dronning Maud Land ice core for atmospheric CO2 changes during the past millennium , 2005 .

[5]  V. Brovkin,et al.  The importance of ocean temperature to global biogeochemistry , 2004 .

[6]  Michael E. Mann,et al.  Global surface temperatures over the past two millennia , 2003 .

[7]  P. Cox,et al.  How positive is the feedback between climate change and the carbon cycle? , 2003 .

[8]  J. Dufresne,et al.  Positive feedback between future climate change and the carbon cycle , 2001 .

[9]  S. Schneider,et al.  Climate Change 2001: Synthesis Report: A contribution of Working Groups I, II, and III to the Third Assessment Report of the Intergovernmental Panel on Climate Change , 2001 .

[10]  Robert J. Scholes,et al.  The Carbon Cycle and Atmospheric Carbon Dioxide , 2001 .

[11]  R. Betts,et al.  Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model , 2000, Nature.

[12]  J. Jouzel,et al.  Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica , 1999, Nature.

[13]  George M. Woodwell,et al.  Biotic Feedbacks in the Warming of the Earth , 1998 .

[14]  B. DeAngelo,et al.  TERRESTRIAL ECOSYSTEM FEEDBACKS TO GLOBAL CLIMATE CHANGE , 1997 .

[15]  D. Etheridge,et al.  Natural and anthropogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn , 1996 .

[16]  G. Woodwell,et al.  Biotic Feedbacks in the Global Climatic System: Will the Warming Feed the Warming? , 1995 .

[17]  U. Siegenthaler,et al.  Ice-age atmospheric concentration of nitrous oxide from an Antarctic ice core , 1992, Nature.

[18]  D. Lashof.  The dynamic greenhouse: Feedback processes that may influence future concentrations of atmospheric trace gases and climatic change , 1989 .

[19]  W. Kellogg.  Feedback mechanisms in the climate system affecting future levels of carbon dioxide , 1983 .

[20]  M. Budyko.  The Earth's climate, past and future , 1982 .

[21]  R. Levins.  The strategy of model building in population biology , 1966 .