Summer dryness in northern midlatitudes due to increased CO sub(2)

Numerical simulations indicate that increases in atmospheric CO sub(2) (and trace gases) could lead to increased summer dryness of the land surface in northern middle and high latitudes, with potentially serious consequences for agriculture. Not all studies support this view, and the validity of the early results has been questioned. The dependence of the original finding upon the representation of the land surface has been investigated. The authors find that the magnitude of the simulated summer drying is dependent upon the physical attributes of the soil, and in certain regions, can be reduced or even reversed by an alternative, but equally plausible, treatment of runoff over frozen ground.