All Climate is Global 2....

While some claim that local effects will overwhelm global changes in climate, the net global effects of such changes will not be all in the same direction and should on the whole cancel out. Global changes on the other hand will push all local climates in the same direction. Some stubbornly resist. Some, of course, are wrong.....

This is the second in a series about such issues.

Recently, overblown results from a FACE experiment (high CO2 growth conditions in fields) stirred up a desert storm about weather (yes Eli does like puns, even bad ones, thank you very much) the Amazon would turn into a desert within the decade. Hiding behind this are a series of Hadley Center studies where carbon cycle models were coupled to climate models that show increasing greenhouse gas concentrations will turn the Amazon into very different place in the century.

Amazonian temperature rises by more than 10L pver the 21st century, and rainfall drops by an alarming 64%. Together these changes lead to a 78% loss in vegetation carbon and a 72% loss in soil carbon. By contrast, over the same period the global mean temperature rises by about 4K and rainfall increases by 3%. Global vegetation carbon increases by about 10 GtC despite the large losses in South American, but global soil carbon decreases by about 155 GtC. The carbon loss in the Amazon basin of about 50 GtC accounts for 23 ppmv of the total CO2 increase of 600 ppmv over the 21st century, or about a third of the total terrestrial carbon reduction of 145 GtC.

An important outcome of such models is that global CO2 increases much faster than in climate models alone. Cox and colleagues considered in detail how this would happen

Cox, P.M., Huntingford, C. and Jones, C.D., 2006: Conditions for sink-to-source transitions and runaway feedbacks from the land carbon-cycle. In Schellnhuber, H.J., Cramer, W., Nakicenovic, N., Wigley, T. and Yohe, G. (eds.) Avoiding Dangerous Climate Change (Cambridge University Press), Chapter 15, 155-161.

Cowling, S.A., Betts, R.A., Cox, P.M., Ettwein, V.J., Jones, C.D., Maslin, M.A. and Spall., S., 2005: Modelling the past and future fate of the Amazonian Rainforest. In Mahli, Y. and Phillips, O. (eds.) Tropical forests and global atmospheric change, (Oxford University Press, Oxford), 191-198.

Gash, J.H.C., Huntingford, C., Marengo, J.A., Betts, R.A., Cox, P.M., Fisch, G., Fu, R., Gandu, A.W., Harris, P.P., Machado, L.A.T., von Randow, C. and Silva Dias, M.A., 2004: Amazonian climate: results and future research. Theor Appl Climatol, 78(1-3), 187-193, doi:10.1007/s00704-004-0052-9.

Huntingford, C., Harris, P.P., Gedney, N., Cox, P.M., Betts, R.A., Gash, J.H.C. and Marengo, J., 2004: Using a GCM analogue model to investigate the potential for Amazonian forest dieback. Theor Appl Climatol, 78(1-3), 177-185, doi:10.1007/s00704-004-0051-x.