ERICE, Sicily  This ancient hilltop town, rife with Roman, Greek, Norman and other influences, is hosting a very modern gathering: a conference on global risks like cyberterrorism, climate change, nuclear weapons and the world’s lagging energy supply.

More than 120 scientists, engineers, analysts and economists from 30 countries were hunkered down here for the 40th annual conference on “planetary emergencies.” The term was coined by Dr. Antonino Zichichi, a native son and a theoretical physicist who has made Erice a hub for experts to discuss persistent, and potentially catastrophic, global challenges.

The participants were not particularly optimistic. They presented data showing that the boom in biofuels was depleting Southeast Asian rain forests, that “bot herders”  computer hackers for hire  were hijacking millions of computers, and that the lack of progress over handling nuclear waste was both hampering the revival of nuclear energy and adding to terrorism risks.

The meetings, which end Sunday, were sponsored by the Erice-based Ettore Majorana Foundation and Center for Scientific Culture and by the World Federation of Scientists in Geneva. Both organizations are led by Dr. Zichichi with what the physicist Dr. Richard L. Garwin, a longtime Erice conference participant and expert on nuclear weapons, affectionately called “imperious” zeal.