STOCKHOLM (Reuters) - Top artificial intelligence executives including OpenAI CEO Sam Altman on Tuesday joined experts and professors in raising the "risk of extinction from AI", which they urged policymakers to equate at par with risks posed by pandemics and nuclear war. "Mitigating the risk of extinction from AI should be a global priority alongside other societal-scale risks such as pandemics and nuclear war," more than 350 signatories wrote in a letter published by the nonprofit Center for AI Safety (CAIS). As well as Altman, they included the CEOs of AI firms DeepMind and Anthropic, and executives from Microsoft and...