Before too much reliance can be placed on these model predictions, however, more attention needs to be placed on the accuracy and precision of the models. Several major problems must be solved: First, a change of one degree centigrade is near the precision of temperature measurements. Although average global temperatures are sometimes quoted to hundredths of a degree, the precision of the dry bulb thermometer, used at almost all weather stations around the world, is 0.5 degree centigrade. Second, the precision of the model in terms of grid size and boundary conditions is limited because of computer constraints. And, finally, several physical processes have been ignored because they are considered of secondary importance, or they are not capable of accurate treatment at this time.