Numerical weather forecast errors are generated by model deficiencies and by errors in the initial conditions which interact and grow nonlinearly. With recent progress in data assimilation, the accuracy in the initial conditions has been substantially improved so that accounting for systematic...

Climatologists have attempted to predict changes in regional climate patterns caused by increasing levels of CO$\sb2$ and other trace gases in the atmosphere. Although the effects of climate are felt at the individual firm level, aggregate effects on crop production will determine if significant...