Changing Interhemisopheric Temperature Asymmetry (image) University of California - Berkeley Share Print E-Mail Caption The top chart shows the steady rise in Northern and Southern Hemisphere temperature since the beginning of the 20th century. The second chart shows little change in the interhemispheric temperature asymmetry (ITA) until the 1980s, when the effect of sulfate aerosols declined as a result of the Clean Air Act. Credit Andrew Friedman, UC Berkeley Usage Restrictions None 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.