Their non-linear character makes predictions of solar activity very difficult. The solar minimum is characterized by a period of decreased solar activity with few, if any, sunspots. Scientists from the National Center for Atmospheric Research (NCAR) also developed a computer model of solar dynamics (Solar dynamo) for more accurate predictions and have confidence in the forecast based upon a series of test runs with the newly developed model simulating the strength of the past eight solar cycles with more than 98% accuracy.