Two decades ago, researchers from Tel Aviv University warned that heat emitted from air-conditioners may contribute to the UHI (urban heat island) effect - metropolitan areas being significantly warmer than their surroundings. "Man-made UHIs cause our cities to be 4Âº-6Âº warmer then rural areas, especially at night. Global warming is still a theory speculating an average temperature rise of 0.5Âº to 1.5Âº over the next 50 years," says physicist Giora Shaviv of the Technion. Recently Shaviv, along with his son, physics Prof. Nir Shaviv of the Hebrew University of Jerusalem, and Prof. Rainer Wehrse of Heidelberg University proposed a revolutionary theory challenging the widely accepted global warming. "We use advanced astrophysical modeling," explains Shaviv. "Increasing carbon dioxide emissions indeed traps radiation from the sun, but also releases longer wave radiation back to space. Our calculations suggest that the release slightly outweighs absorption, which results in global cooling, not warming. Ours is a minority view, but whether we are right or wrong, UHI is a much more imminent and severe threat than global worming. And the best remedy is sustainable green building."