Varied Cloud Cover (image) Uppsala University Share Print E-Mail Caption Varied cloud cover, such as here outside the Angstrom Laboratory at Uppsala University, makes reliable forecasts of solar irradiance challenging. Credit Joakim Munkhammar Usage Restrictions To accompany coverage of Joakim Munkhammar's research. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.