On multiple solutions of the atmosphere–vegetation system in present‐day climate

An asynchronously coupled global atmosphere‐biome model is used to assess the stability of the atmosphere‐vegetation system under present-day conditions of solar irradiation and sea-surface temperatures. When initialized with different land-surface conditions (1, the continents, except for regions of inland ice, completely covered with forest; 2, with grassland; 3, with (dark) desert; and 4, with (bright) sand desert), the atmosphere‐biome model finds two equilibrium solutions: the first solution yields the present-day distribution of subtropical deserts, the second reveals a moister climate in North Africa and Central East Asia and thereby a northward shift of vegetation particularly in the south-western Sahara. The first solution is obtained with initial condition 4, and the second with 1, 2, 3. When comparing these results with an earlier study of biogeophysical feedback in the African and Asian monsoon area, it can be concluded that North Africa is probably the region on Earth which is most sensitive considering bifurcations of the atmosphere‐vegetation system at the global scale.

[1]  M. Claussen,et al.  Simulation of the global bio-geophysical interactions during the Last Glacial Maximum , 1998 .

[2]  B. Barkstrom,et al.  Cloud-Radiative Forcing and Climate: Results from the Earth Radiation Budget Experiment , 1989, Science.

[3]  G. Meehl.  Influence of the land surface in the Asian summer monsoon , 1994 .

[4]  W. Köppen.  Das geographische System der Klimate , 1936 .

[5]  J. Charney,et al.  Drought in the Sahara: A Biogeophysical Feedback Mechanism , 1975, Science.

[6]  R. Leemans,et al.  Comparing global vegetation maps with the Kappa statistic , 1992 .

[7]  Aurélie Botta,et al.  Possible role of atmosphere-biosphere interactions in triggering the last glaciation , 1996 .

[8]  M. Claussen,et al.  The atmospheric general circulation model ECHAM-4: Model description and simulation of present-day climate , 1996 .

[9]  Veronika Gayler,et al.  The greening of the Sahara during the mid-Holocene: results of an interactive atmosphere-biome model , 1997 .

[10]  D. Legates,et al.  Mean seasonal and spatial variability in gauge‐corrected, global precipitation , 1990 .

[11]  H. Storch.  Inconsistencies at the interface of climate impact studies and global climate research , 1992 .

[12]  Robert Sausen,et al.  Simulation of the present-day climate with the ECHAM model: Impact of model physics and resolution , 1992 .

[13]  J. Louis.  A parametric model of vertical eddy fluxes in the atmosphere , 1979 .

[14]  W. Cramer,et al.  The IIASA database for mean monthly values of temperature , 1991 .

[15]  M. Claussen.  On coupling global biome models with climate models , 1994 .

[16]  M. Claussen.  Modeling bio-geophysical feedback in the African and Indian monsoon region , 1997 .

[17]  E. Lorenz.  Maximum Simplification of the Dynamic Equations , 1960 .

[18]  E. Todini,et al.  A rainfall–runoff scheme for use in the Hamburg climate model , 1992 .

[19]  J. Kutzbach,et al.  Vegetation and soil feedbacks on the response of the African monsoon to orbital forcing in the early to middle Holocene , 1996, Nature.

[20]  J. Kutzbach,et al.  Feedbacks between climate and boreal forests during the Holocene epoch , 1994, Nature.

[21]  S. Rahmstorf.  On the freshwater forcing and transport of the Atlantic thermohaline circulation , 1996 .

[22]  W. Cramer,et al.  A global biome model based on plant physiology and dominance, soil properties and climate , 1992 .

[23]  M. Wild,et al.  Regional climate simulation with a high resolution GCM: surface hydrology , 1996 .

[24]  K. Arpe,et al.  The Hydrological Cycle in the ECHAM3 Simulations of the Atmospheric Circulation , 1994 .

[25]  G. Bonan,et al.  Effects of boreal forest vegetation on global climate , 1992, Nature.

[26]  J. Charney.  Dynamics of deserts and drought in the Sahel , 1975 .

[27]  A. Henderson-Sellers,et al.  Continental vegetation as a dynamic component of a global climate model: a preliminary assessment , 1993 .